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Initial vendor packages

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Signed-off-by: Valentin Popov <valentin@popov.link>
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Valentin Popov
2024-01-08 01:21:28 +04:00
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This project is dual-licensed under the Unlicense and MIT licenses.
You may use this code under the terms of either license.

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# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
#
# When uploading crates to the registry Cargo will automatically
# "normalize" Cargo.toml files for maximal compatibility
# with all versions of Cargo and also rewrite `path` dependencies
# to registry (e.g., crates.io) dependencies.
#
# If you are reading this file be aware that the original Cargo.toml
# will likely look very different (and much more reasonable).
# See Cargo.toml.orig for the original contents.
[package]
edition = "2021"
rust-version = "1.61"
name = "memchr"
version = "2.7.1"
authors = [
"Andrew Gallant <jamslam@gmail.com>",
"bluss",
]
exclude = [
"/.github",
"/benchmarks",
"/fuzz",
"/scripts",
"/tmp",
]
description = """
Provides extremely fast (uses SIMD on x86_64, aarch64 and wasm32) routines for
1, 2 or 3 byte search and single substring search.
"""
homepage = "https://github.com/BurntSushi/memchr"
documentation = "https://docs.rs/memchr/"
readme = "README.md"
keywords = [
"memchr",
"memmem",
"substring",
"find",
"search",
]
license = "Unlicense OR MIT"
repository = "https://github.com/BurntSushi/memchr"
[package.metadata.docs.rs]
rustdoc-args = ["--generate-link-to-definition"]
[profile.bench]
debug = 2
[profile.release]
debug = 2
[profile.test]
opt-level = 3
debug = 2
[lib]
name = "memchr"
bench = false
[dependencies.compiler_builtins]
version = "0.1.2"
optional = true
[dependencies.core]
version = "1.0.0"
optional = true
package = "rustc-std-workspace-core"
[dependencies.log]
version = "0.4.20"
optional = true
[dev-dependencies.quickcheck]
version = "1.0.3"
default-features = false
[features]
alloc = []
default = ["std"]
libc = []
logging = ["dep:log"]
rustc-dep-of-std = [
"core",
"compiler_builtins",
]
std = ["alloc"]
use_std = ["std"]

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The MIT License (MIT)
Copyright (c) 2015 Andrew Gallant
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

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memchr
======
This library provides heavily optimized routines for string search primitives.
[![Build status](https://github.com/BurntSushi/memchr/workflows/ci/badge.svg)](https://github.com/BurntSushi/memchr/actions)
[![Crates.io](https://img.shields.io/crates/v/memchr.svg)](https://crates.io/crates/memchr)
Dual-licensed under MIT or the [UNLICENSE](https://unlicense.org/).
### Documentation
[https://docs.rs/memchr](https://docs.rs/memchr)
### Overview
* The top-level module provides routines for searching for 1, 2 or 3 bytes
in the forward or reverse direction. When searching for more than one byte,
positions are considered a match if the byte at that position matches any
of the bytes.
* The `memmem` sub-module provides forward and reverse substring search
routines.
In all such cases, routines operate on `&[u8]` without regard to encoding. This
is exactly what you want when searching either UTF-8 or arbitrary bytes.
### Compiling without the standard library
memchr links to the standard library by default, but you can disable the
`std` feature if you want to use it in a `#![no_std]` crate:
```toml
[dependencies]
memchr = { version = "2", default-features = false }
```
On `x86_64` platforms, when the `std` feature is disabled, the SSE2 accelerated
implementations will be used. When `std` is enabled, AVX2 accelerated
implementations will be used if the CPU is determined to support it at runtime.
SIMD accelerated routines are also available on the `wasm32` and `aarch64`
targets. The `std` feature is not required to use them.
When a SIMD version is not available, then this crate falls back to
[SWAR](https://en.wikipedia.org/wiki/SWAR) techniques.
### Minimum Rust version policy
This crate's minimum supported `rustc` version is `1.61.0`.
The current policy is that the minimum Rust version required to use this crate
can be increased in minor version updates. For example, if `crate 1.0` requires
Rust 1.20.0, then `crate 1.0.z` for all values of `z` will also require Rust
1.20.0 or newer. However, `crate 1.y` for `y > 0` may require a newer minimum
version of Rust.
In general, this crate will be conservative with respect to the minimum
supported version of Rust.
### Testing strategy
Given the complexity of the code in this crate, along with the pervasive use
of `unsafe`, this crate has an extensive testing strategy. It combines multiple
approaches:
* Hand-written tests.
* Exhaustive-style testing meant to exercise all possible branching and offset
calculations.
* Property based testing through [`quickcheck`](https://github.com/BurntSushi/quickcheck).
* Fuzz testing through [`cargo fuzz`](https://github.com/rust-fuzz/cargo-fuzz).
* A huge suite of benchmarks that are also run as tests. Benchmarks always
confirm that the expected result occurs.
Improvements to the testing infrastructure are very welcome.
### Algorithms used
At time of writing, this crate's implementation of substring search actually
has a few different algorithms to choose from depending on the situation.
* For very small haystacks,
[Rabin-Karp](https://en.wikipedia.org/wiki/Rabin%E2%80%93Karp_algorithm)
is used to reduce latency. Rabin-Karp has very small overhead and can often
complete before other searchers have even been constructed.
* For small needles, a variant of the
["Generic SIMD"](http://0x80.pl/articles/simd-strfind.html#algorithm-1-generic-simd)
algorithm is used. Instead of using the first and last bytes, a heuristic is
used to select bytes based on a background distribution of byte frequencies.
* In all other cases,
[Two-Way](https://en.wikipedia.org/wiki/Two-way_string-matching_algorithm)
is used. If possible, a prefilter based on the "Generic SIMD" algorithm
linked above is used to find candidates quickly. A dynamic heuristic is used
to detect if the prefilter is ineffective, and if so, disables it.
### Why is the standard library's substring search so much slower?
We'll start by establishing what the difference in performance actually
is. There are two relevant benchmark classes to consider: `prebuilt` and
`oneshot`. The `prebuilt` benchmarks are designed to measure---to the extent
possible---search time only. That is, the benchmark first starts by building a
searcher and then only tracking the time for _using_ the searcher:
```
$ rebar rank benchmarks/record/x86_64/2023-08-26.csv --intersection -e memchr/memmem/prebuilt -e std/memmem/prebuilt
Engine Version Geometric mean of speed ratios Benchmark count
------ ------- ------------------------------ ---------------
rust/memchr/memmem/prebuilt 2.5.0 1.03 53
rust/std/memmem/prebuilt 1.73.0-nightly 180dffba1 6.50 53
```
Conversely, the `oneshot` benchmark class measures the time it takes to both
build the searcher _and_ use it:
```
$ rebar rank benchmarks/record/x86_64/2023-08-26.csv --intersection -e memchr/memmem/oneshot -e std/memmem/oneshot
Engine Version Geometric mean of speed ratios Benchmark count
------ ------- ------------------------------ ---------------
rust/memchr/memmem/oneshot 2.5.0 1.04 53
rust/std/memmem/oneshot 1.73.0-nightly 180dffba1 5.26 53
```
**NOTE:** Replace `rebar rank` with `rebar cmp` in the above commands to
explore the specific benchmarks and their differences.
So in both cases, this crate is quite a bit faster over a broad sampling of
benchmarks regardless of whether you measure only search time or search time
plus construction time. The difference is a little smaller when you include
construction time in your measurements.
These two different types of benchmark classes make for a nice segue into
one reason why the standard library's substring search can be slower: API
design. In the standard library, the only APIs available to you require
one to re-construct the searcher for every search. While you can benefit
from building a searcher once and iterating over all matches in a single
string, you cannot reuse that searcher to search other strings. This might
come up when, for example, searching a file one line at a time. You'll need
to re-build the searcher for every line searched, and this can [really
matter][burntsushi-bstr-blog].
**NOTE:** The `prebuilt` benchmark for the standard library can't actually
avoid measuring searcher construction at some level, because there is no API
for it. Instead, the benchmark consists of building the searcher once and then
finding all matches in a single string via an iterator. This tends to
approximate a benchmark where searcher construction isn't measured, but it
isn't perfect. While this means the comparison is not strictly
apples-to-apples, it does reflect what is maximally possible with the standard
library, and thus reflects the best that one could do in a real world scenario.
While there is more to the story than just API design here, it's important to
point out that even if the standard library's substring search were a precise
clone of this crate internally, it would still be at a disadvantage in some
workloads because of its API. (The same also applies to C's standard library
`memmem` function. There is no way to amortize construction of the searcher.
You need to pay for it on every call.)
The other reason for the difference in performance is that
the standard library has trouble using SIMD. In particular, substring search
is implemented in the `core` library, where platform specific code generally
can't exist. That's an issue because in order to utilize SIMD beyond SSE2
while maintaining portable binaries, one needs to use [dynamic CPU feature
detection][dynamic-cpu], and that in turn requires platform specific code.
While there is [an RFC for enabling target feature detection in
`core`][core-feature], it doesn't yet exist.
The bottom line here is that `core`'s substring search implementation is
limited to making use of SSE2, but not AVX.
Still though, this crate does accelerate substring search even when only SSE2
is available. The standard library could therefore adopt the techniques in this
crate just for SSE2. The reason why that hasn't happened yet isn't totally
clear to me. It likely needs a champion to push it through. The standard
library tends to be more conservative in these things. With that said, the
standard library does use some [SSE2 acceleration on `x86-64`][std-sse2] added
in [this PR][std-sse2-pr]. However, at the time of writing, it is only used
for short needles and doesn't use the frequency based heuristics found in this
crate.
**NOTE:** Another thing worth mentioning is that the standard library's
substring search routine requires that both the needle and haystack have type
`&str`. Unless you can assume that your data is valid UTF-8, building a `&str`
will come with the overhead of UTF-8 validation. This may in turn result in
overall slower searching depending on your workload. In contrast, the `memchr`
crate permits both the needle and the haystack to have type `&[u8]`, where
`&[u8]` can be created from a `&str` with zero cost. Therefore, the substring
search in this crate is strictly more flexible than what the standard library
provides.
[burntsushi-bstr-blog]: https://blog.burntsushi.net/bstr/#motivation-based-on-performance
[dynamic-cpu]: https://doc.rust-lang.org/std/arch/index.html#dynamic-cpu-feature-detection
[core-feature]: https://github.com/rust-lang/rfcs/pull/3469
[std-sse2]: https://github.com/rust-lang/rust/blob/bf9229a2e366b4c311f059014a4aa08af16de5d8/library/core/src/str/pattern.rs#L1719-L1857
[std-sse2-pr]: https://github.com/rust-lang/rust/pull/103779

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This is free and unencumbered software released into the public domain.
Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.
In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.
For more information, please refer to <http://unlicense.org/>

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max_width = 79
use_small_heuristics = "max"

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/*!
Wrapper routines for `memchr` and friends.
These routines choose the best implementation at compile time. (This is
different from `x86_64` because it is expected that `neon` is almost always
available for `aarch64` targets.)
*/
macro_rules! defraw {
($ty:ident, $find:ident, $start:ident, $end:ident, $($needles:ident),+) => {{
#[cfg(target_feature = "neon")]
{
use crate::arch::aarch64::neon::memchr::$ty;
debug!("chose neon for {}", stringify!($ty));
debug_assert!($ty::is_available());
// SAFETY: We know that wasm memchr is always available whenever
// code is compiled for `aarch64` with the `neon` target feature
// enabled.
$ty::new_unchecked($($needles),+).$find($start, $end)
}
#[cfg(not(target_feature = "neon"))]
{
use crate::arch::all::memchr::$ty;
debug!(
"no neon feature available, using fallback for {}",
stringify!($ty),
);
$ty::new($($needles),+).$find($start, $end)
}
}}
}
/// memchr, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::find_raw`.
#[inline(always)]
pub(crate) unsafe fn memchr_raw(
n1: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(One, find_raw, start, end, n1)
}
/// memrchr, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::rfind_raw`.
#[inline(always)]
pub(crate) unsafe fn memrchr_raw(
n1: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(One, rfind_raw, start, end, n1)
}
/// memchr2, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Two::find_raw`.
#[inline(always)]
pub(crate) unsafe fn memchr2_raw(
n1: u8,
n2: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(Two, find_raw, start, end, n1, n2)
}
/// memrchr2, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Two::rfind_raw`.
#[inline(always)]
pub(crate) unsafe fn memrchr2_raw(
n1: u8,
n2: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(Two, rfind_raw, start, end, n1, n2)
}
/// memchr3, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Three::find_raw`.
#[inline(always)]
pub(crate) unsafe fn memchr3_raw(
n1: u8,
n2: u8,
n3: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(Three, find_raw, start, end, n1, n2, n3)
}
/// memrchr3, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Three::rfind_raw`.
#[inline(always)]
pub(crate) unsafe fn memrchr3_raw(
n1: u8,
n2: u8,
n3: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(Three, rfind_raw, start, end, n1, n2, n3)
}
/// Count all matching bytes, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::count_raw`.
#[inline(always)]
pub(crate) unsafe fn count_raw(
n1: u8,
start: *const u8,
end: *const u8,
) -> usize {
defraw!(One, count_raw, start, end, n1)
}

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/*!
Vector algorithms for the `aarch64` target.
*/
pub mod neon;
pub(crate) mod memchr;

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/*!
Algorithms for the `aarch64` target using 128-bit vectors via NEON.
*/
pub mod memchr;
pub mod packedpair;

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/*!
A 128-bit vector implementation of the "packed pair" SIMD algorithm.
The "packed pair" algorithm is based on the [generic SIMD] algorithm. The main
difference is that it (by default) uses a background distribution of byte
frequencies to heuristically select the pair of bytes to search for.
[generic SIMD]: http://0x80.pl/articles/simd-strfind.html#first-and-last
*/
use core::arch::aarch64::uint8x16_t;
use crate::arch::{all::packedpair::Pair, generic::packedpair};
/// A "packed pair" finder that uses 128-bit vector operations.
///
/// This finder picks two bytes that it believes have high predictive power
/// for indicating an overall match of a needle. Depending on whether
/// `Finder::find` or `Finder::find_prefilter` is used, it reports offsets
/// where the needle matches or could match. In the prefilter case, candidates
/// are reported whenever the [`Pair`] of bytes given matches.
#[derive(Clone, Copy, Debug)]
pub struct Finder(packedpair::Finder<uint8x16_t>);
/// A "packed pair" finder that uses 128-bit vector operations.
///
/// This finder picks two bytes that it believes have high predictive power
/// for indicating an overall match of a needle. Depending on whether
/// `Finder::find` or `Finder::find_prefilter` is used, it reports offsets
/// where the needle matches or could match. In the prefilter case, candidates
/// are reported whenever the [`Pair`] of bytes given matches.
impl Finder {
/// Create a new pair searcher. The searcher returned can either report
/// exact matches of `needle` or act as a prefilter and report candidate
/// positions of `needle`.
///
/// If neon is unavailable in the current environment or if a [`Pair`]
/// could not be constructed from the needle given, then `None` is
/// returned.
#[inline]
pub fn new(needle: &[u8]) -> Option<Finder> {
Finder::with_pair(needle, Pair::new(needle)?)
}
/// Create a new "packed pair" finder using the pair of bytes given.
///
/// This constructor permits callers to control precisely which pair of
/// bytes is used as a predicate.
///
/// If neon is unavailable in the current environment, then `None` is
/// returned.
#[inline]
pub fn with_pair(needle: &[u8], pair: Pair) -> Option<Finder> {
if Finder::is_available() {
// SAFETY: we check that sse2 is available above. We are also
// guaranteed to have needle.len() > 1 because we have a valid
// Pair.
unsafe { Some(Finder::with_pair_impl(needle, pair)) }
} else {
None
}
}
/// Create a new `Finder` specific to neon vectors and routines.
///
/// # Safety
///
/// Same as the safety for `packedpair::Finder::new`, and callers must also
/// ensure that neon is available.
#[target_feature(enable = "neon")]
#[inline]
unsafe fn with_pair_impl(needle: &[u8], pair: Pair) -> Finder {
let finder = packedpair::Finder::<uint8x16_t>::new(needle, pair);
Finder(finder)
}
/// Returns true when this implementation is available in the current
/// environment.
///
/// When this is true, it is guaranteed that [`Finder::with_pair`] will
/// return a `Some` value. Similarly, when it is false, it is guaranteed
/// that `Finder::with_pair` will return a `None` value. Notice that this
/// does not guarantee that [`Finder::new`] will return a `Finder`. Namely,
/// even when `Finder::is_available` is true, it is not guaranteed that a
/// valid [`Pair`] can be found from the needle given.
///
/// Note also that for the lifetime of a single program, if this returns
/// true then it will always return true.
#[inline]
pub fn is_available() -> bool {
#[cfg(target_feature = "neon")]
{
true
}
#[cfg(not(target_feature = "neon"))]
{
false
}
}
/// Execute a search using neon vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
#[inline]
pub fn find(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
// SAFETY: Building a `Finder` means it's safe to call 'neon' routines.
unsafe { self.find_impl(haystack, needle) }
}
/// Execute a search using neon vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
#[inline]
pub fn find_prefilter(&self, haystack: &[u8]) -> Option<usize> {
// SAFETY: Building a `Finder` means it's safe to call 'neon' routines.
unsafe { self.find_prefilter_impl(haystack) }
}
/// Execute a search using neon vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
///
/// # Safety
///
/// (The target feature safety obligation is automatically fulfilled by
/// virtue of being a method on `Finder`, which can only be constructed
/// when it is safe to call `neon` routines.)
#[target_feature(enable = "neon")]
#[inline]
unsafe fn find_impl(
&self,
haystack: &[u8],
needle: &[u8],
) -> Option<usize> {
self.0.find(haystack, needle)
}
/// Execute a prefilter search using neon vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
///
/// # Safety
///
/// (The target feature safety obligation is automatically fulfilled by
/// virtue of being a method on `Finder`, which can only be constructed
/// when it is safe to call `neon` routines.)
#[target_feature(enable = "neon")]
#[inline]
unsafe fn find_prefilter_impl(&self, haystack: &[u8]) -> Option<usize> {
self.0.find_prefilter(haystack)
}
/// Returns the pair of offsets (into the needle) used to check as a
/// predicate before confirming whether a needle exists at a particular
/// position.
#[inline]
pub fn pair(&self) -> &Pair {
self.0.pair()
}
/// Returns the minimum haystack length that this `Finder` can search.
///
/// Using a haystack with length smaller than this in a search will result
/// in a panic. The reason for this restriction is that this finder is
/// meant to be a low-level component that is part of a larger substring
/// strategy. In that sense, it avoids trying to handle all cases and
/// instead only handles the cases that it can handle very well.
#[inline]
pub fn min_haystack_len(&self) -> usize {
self.0.min_haystack_len()
}
}
#[cfg(test)]
mod tests {
use super::*;
fn find(haystack: &[u8], needle: &[u8]) -> Option<Option<usize>> {
let f = Finder::new(needle)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find(haystack, needle))
}
define_substring_forward_quickcheck!(find);
#[test]
fn forward_substring() {
crate::tests::substring::Runner::new().fwd(find).run()
}
#[test]
fn forward_packedpair() {
fn find(
haystack: &[u8],
needle: &[u8],
index1: u8,
index2: u8,
) -> Option<Option<usize>> {
let pair = Pair::with_indices(needle, index1, index2)?;
let f = Finder::with_pair(needle, pair)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find(haystack, needle))
}
crate::tests::packedpair::Runner::new().fwd(find).run()
}
#[test]
fn forward_packedpair_prefilter() {
fn find(
haystack: &[u8],
needle: &[u8],
index1: u8,
index2: u8,
) -> Option<Option<usize>> {
let pair = Pair::with_indices(needle, index1, index2)?;
let f = Finder::with_pair(needle, pair)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find_prefilter(haystack))
}
crate::tests::packedpair::Runner::new().fwd(find).run()
}
}

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/*!
Provides architecture independent implementations of `memchr` and friends.
The main types in this module are [`One`], [`Two`] and [`Three`]. They are for
searching for one, two or three distinct bytes, respectively, in a haystack.
Each type also has corresponding double ended iterators. These searchers
are typically slower than hand-coded vector routines accomplishing the same
task, but are also typically faster than naive scalar code. These routines
effectively work by treating a `usize` as a vector of 8-bit lanes, and thus
achieves some level of data parallelism even without explicit vector support.
The `One` searcher also provides a [`One::count`] routine for efficiently
counting the number of times a single byte occurs in a haystack. This is
useful, for example, for counting the number of lines in a haystack. This
routine exists because it is usually faster, especially with a high match
count, then using [`One::find`] repeatedly. ([`OneIter`] specializes its
`Iterator::count` implementation to use this routine.)
Only one, two and three bytes are supported because three bytes is about
the point where one sees diminishing returns. Beyond this point and it's
probably (but not necessarily) better to just use a simple `[bool; 256]` array
or similar. However, it depends mightily on the specific work-load and the
expected match frequency.
*/
use crate::{arch::generic::memchr as generic, ext::Pointer};
/// The number of bytes in a single `usize` value.
const USIZE_BYTES: usize = (usize::BITS / 8) as usize;
/// The bits that must be zero for a `*const usize` to be properly aligned.
const USIZE_ALIGN: usize = USIZE_BYTES - 1;
/// Finds all occurrences of a single byte in a haystack.
#[derive(Clone, Copy, Debug)]
pub struct One {
s1: u8,
v1: usize,
}
impl One {
/// The number of bytes we examine per each iteration of our search loop.
const LOOP_BYTES: usize = 2 * USIZE_BYTES;
/// Create a new searcher that finds occurrences of the byte given.
#[inline]
pub fn new(needle: u8) -> One {
One { s1: needle, v1: splat(needle) }
}
/// A test-only routine so that we can bundle a bunch of quickcheck
/// properties into a single macro. Basically, this provides a constructor
/// that makes it identical to most other memchr implementations, which
/// have fallible constructors.
#[cfg(test)]
pub(crate) fn try_new(needle: u8) -> Option<One> {
Some(One::new(needle))
}
/// Return the first occurrence of the needle in the given haystack. If no
/// such occurrence exists, then `None` is returned.
///
/// The occurrence is reported as an offset into `haystack`. Its maximum
/// value for a non-empty haystack is `haystack.len() - 1`.
#[inline]
pub fn find(&self, haystack: &[u8]) -> Option<usize> {
// SAFETY: `find_raw` guarantees that if a pointer is returned, it
// falls within the bounds of the start and end pointers.
unsafe {
generic::search_slice_with_raw(haystack, |s, e| {
self.find_raw(s, e)
})
}
}
/// Return the last occurrence of the needle in the given haystack. If no
/// such occurrence exists, then `None` is returned.
///
/// The occurrence is reported as an offset into `haystack`. Its maximum
/// value for a non-empty haystack is `haystack.len() - 1`.
#[inline]
pub fn rfind(&self, haystack: &[u8]) -> Option<usize> {
// SAFETY: `find_raw` guarantees that if a pointer is returned, it
// falls within the bounds of the start and end pointers.
unsafe {
generic::search_slice_with_raw(haystack, |s, e| {
self.rfind_raw(s, e)
})
}
}
/// Counts all occurrences of this byte in the given haystack.
#[inline]
pub fn count(&self, haystack: &[u8]) -> usize {
// SAFETY: All of our pointers are derived directly from a borrowed
// slice, which is guaranteed to be valid.
unsafe {
let start = haystack.as_ptr();
let end = start.add(haystack.len());
self.count_raw(start, end)
}
}
/// Like `find`, but accepts and returns raw pointers.
///
/// When a match is found, the pointer returned is guaranteed to be
/// `>= start` and `< end`.
///
/// This routine is useful if you're already using raw pointers and would
/// like to avoid converting back to a slice before executing a search.
///
/// # Safety
///
/// * Both `start` and `end` must be valid for reads.
/// * Both `start` and `end` must point to an initialized value.
/// * Both `start` and `end` must point to the same allocated object and
/// must either be in bounds or at most one byte past the end of the
/// allocated object.
/// * Both `start` and `end` must be _derived from_ a pointer to the same
/// object.
/// * The distance between `start` and `end` must not overflow `isize`.
/// * The distance being in bounds must not rely on "wrapping around" the
/// address space.
///
/// Note that callers may pass a pair of pointers such that `start >= end`.
/// In that case, `None` will always be returned.
#[inline]
pub unsafe fn find_raw(
&self,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
if start >= end {
return None;
}
let confirm = |b| self.confirm(b);
let len = end.distance(start);
if len < USIZE_BYTES {
return generic::fwd_byte_by_byte(start, end, confirm);
}
// The start of the search may not be aligned to `*const usize`,
// so we do an unaligned load here.
let chunk = start.cast::<usize>().read_unaligned();
if self.has_needle(chunk) {
return generic::fwd_byte_by_byte(start, end, confirm);
}
// And now we start our search at a guaranteed aligned position.
// The first iteration of the loop below will overlap with the the
// unaligned chunk above in cases where the search starts at an
// unaligned offset, but that's okay as we're only here if that
// above didn't find a match.
let mut cur =
start.add(USIZE_BYTES - (start.as_usize() & USIZE_ALIGN));
debug_assert!(cur > start);
if len <= One::LOOP_BYTES {
return generic::fwd_byte_by_byte(cur, end, confirm);
}
debug_assert!(end.sub(One::LOOP_BYTES) >= start);
while cur <= end.sub(One::LOOP_BYTES) {
debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES);
let a = cur.cast::<usize>().read();
let b = cur.add(USIZE_BYTES).cast::<usize>().read();
if self.has_needle(a) || self.has_needle(b) {
break;
}
cur = cur.add(One::LOOP_BYTES);
}
generic::fwd_byte_by_byte(cur, end, confirm)
}
/// Like `rfind`, but accepts and returns raw pointers.
///
/// When a match is found, the pointer returned is guaranteed to be
/// `>= start` and `< end`.
///
/// This routine is useful if you're already using raw pointers and would
/// like to avoid converting back to a slice before executing a search.
///
/// # Safety
///
/// * Both `start` and `end` must be valid for reads.
/// * Both `start` and `end` must point to an initialized value.
/// * Both `start` and `end` must point to the same allocated object and
/// must either be in bounds or at most one byte past the end of the
/// allocated object.
/// * Both `start` and `end` must be _derived from_ a pointer to the same
/// object.
/// * The distance between `start` and `end` must not overflow `isize`.
/// * The distance being in bounds must not rely on "wrapping around" the
/// address space.
///
/// Note that callers may pass a pair of pointers such that `start >= end`.
/// In that case, `None` will always be returned.
#[inline]
pub unsafe fn rfind_raw(
&self,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
if start >= end {
return None;
}
let confirm = |b| self.confirm(b);
let len = end.distance(start);
if len < USIZE_BYTES {
return generic::rev_byte_by_byte(start, end, confirm);
}
let chunk = end.sub(USIZE_BYTES).cast::<usize>().read_unaligned();
if self.has_needle(chunk) {
return generic::rev_byte_by_byte(start, end, confirm);
}
let mut cur = end.sub(end.as_usize() & USIZE_ALIGN);
debug_assert!(start <= cur && cur <= end);
if len <= One::LOOP_BYTES {
return generic::rev_byte_by_byte(start, cur, confirm);
}
while cur >= start.add(One::LOOP_BYTES) {
debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES);
let a = cur.sub(2 * USIZE_BYTES).cast::<usize>().read();
let b = cur.sub(1 * USIZE_BYTES).cast::<usize>().read();
if self.has_needle(a) || self.has_needle(b) {
break;
}
cur = cur.sub(One::LOOP_BYTES);
}
generic::rev_byte_by_byte(start, cur, confirm)
}
/// Counts all occurrences of this byte in the given haystack represented
/// by raw pointers.
///
/// This routine is useful if you're already using raw pointers and would
/// like to avoid converting back to a slice before executing a search.
///
/// # Safety
///
/// * Both `start` and `end` must be valid for reads.
/// * Both `start` and `end` must point to an initialized value.
/// * Both `start` and `end` must point to the same allocated object and
/// must either be in bounds or at most one byte past the end of the
/// allocated object.
/// * Both `start` and `end` must be _derived from_ a pointer to the same
/// object.
/// * The distance between `start` and `end` must not overflow `isize`.
/// * The distance being in bounds must not rely on "wrapping around" the
/// address space.
///
/// Note that callers may pass a pair of pointers such that `start >= end`.
/// In that case, `0` will always be returned.
#[inline]
pub unsafe fn count_raw(&self, start: *const u8, end: *const u8) -> usize {
if start >= end {
return 0;
}
// Sadly I couldn't get the SWAR approach to work here, so we just do
// one byte at a time for now. PRs to improve this are welcome.
let mut ptr = start;
let mut count = 0;
while ptr < end {
count += (ptr.read() == self.s1) as usize;
ptr = ptr.offset(1);
}
count
}
/// Returns an iterator over all occurrences of the needle byte in the
/// given haystack.
///
/// The iterator returned implements `DoubleEndedIterator`. This means it
/// can also be used to find occurrences in reverse order.
pub fn iter<'a, 'h>(&'a self, haystack: &'h [u8]) -> OneIter<'a, 'h> {
OneIter { searcher: self, it: generic::Iter::new(haystack) }
}
#[inline(always)]
fn has_needle(&self, chunk: usize) -> bool {
has_zero_byte(self.v1 ^ chunk)
}
#[inline(always)]
fn confirm(&self, haystack_byte: u8) -> bool {
self.s1 == haystack_byte
}
}
/// An iterator over all occurrences of a single byte in a haystack.
///
/// This iterator implements `DoubleEndedIterator`, which means it can also be
/// used to find occurrences in reverse order.
///
/// This iterator is created by the [`One::iter`] method.
///
/// The lifetime parameters are as follows:
///
/// * `'a` refers to the lifetime of the underlying [`One`] searcher.
/// * `'h` refers to the lifetime of the haystack being searched.
#[derive(Clone, Debug)]
pub struct OneIter<'a, 'h> {
/// The underlying memchr searcher.
searcher: &'a One,
/// Generic iterator implementation.
it: generic::Iter<'h>,
}
impl<'a, 'h> Iterator for OneIter<'a, 'h> {
type Item = usize;
#[inline]
fn next(&mut self) -> Option<usize> {
// SAFETY: We rely on the generic iterator to provide valid start
// and end pointers, but we guarantee that any pointer returned by
// 'find_raw' falls within the bounds of the start and end pointer.
unsafe { self.it.next(|s, e| self.searcher.find_raw(s, e)) }
}
#[inline]
fn count(self) -> usize {
self.it.count(|s, e| {
// SAFETY: We rely on our generic iterator to return valid start
// and end pointers.
unsafe { self.searcher.count_raw(s, e) }
})
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.it.size_hint()
}
}
impl<'a, 'h> DoubleEndedIterator for OneIter<'a, 'h> {
#[inline]
fn next_back(&mut self) -> Option<usize> {
// SAFETY: We rely on the generic iterator to provide valid start
// and end pointers, but we guarantee that any pointer returned by
// 'rfind_raw' falls within the bounds of the start and end pointer.
unsafe { self.it.next_back(|s, e| self.searcher.rfind_raw(s, e)) }
}
}
/// Finds all occurrences of two bytes in a haystack.
///
/// That is, this reports matches of one of two possible bytes. For example,
/// searching for `a` or `b` in `afoobar` would report matches at offsets `0`,
/// `4` and `5`.
#[derive(Clone, Copy, Debug)]
pub struct Two {
s1: u8,
s2: u8,
v1: usize,
v2: usize,
}
impl Two {
/// Create a new searcher that finds occurrences of the two needle bytes
/// given.
#[inline]
pub fn new(needle1: u8, needle2: u8) -> Two {
Two {
s1: needle1,
s2: needle2,
v1: splat(needle1),
v2: splat(needle2),
}
}
/// A test-only routine so that we can bundle a bunch of quickcheck
/// properties into a single macro. Basically, this provides a constructor
/// that makes it identical to most other memchr implementations, which
/// have fallible constructors.
#[cfg(test)]
pub(crate) fn try_new(needle1: u8, needle2: u8) -> Option<Two> {
Some(Two::new(needle1, needle2))
}
/// Return the first occurrence of one of the needle bytes in the given
/// haystack. If no such occurrence exists, then `None` is returned.
///
/// The occurrence is reported as an offset into `haystack`. Its maximum
/// value for a non-empty haystack is `haystack.len() - 1`.
#[inline]
pub fn find(&self, haystack: &[u8]) -> Option<usize> {
// SAFETY: `find_raw` guarantees that if a pointer is returned, it
// falls within the bounds of the start and end pointers.
unsafe {
generic::search_slice_with_raw(haystack, |s, e| {
self.find_raw(s, e)
})
}
}
/// Return the last occurrence of one of the needle bytes in the given
/// haystack. If no such occurrence exists, then `None` is returned.
///
/// The occurrence is reported as an offset into `haystack`. Its maximum
/// value for a non-empty haystack is `haystack.len() - 1`.
#[inline]
pub fn rfind(&self, haystack: &[u8]) -> Option<usize> {
// SAFETY: `find_raw` guarantees that if a pointer is returned, it
// falls within the bounds of the start and end pointers.
unsafe {
generic::search_slice_with_raw(haystack, |s, e| {
self.rfind_raw(s, e)
})
}
}
/// Like `find`, but accepts and returns raw pointers.
///
/// When a match is found, the pointer returned is guaranteed to be
/// `>= start` and `< end`.
///
/// This routine is useful if you're already using raw pointers and would
/// like to avoid converting back to a slice before executing a search.
///
/// # Safety
///
/// * Both `start` and `end` must be valid for reads.
/// * Both `start` and `end` must point to an initialized value.
/// * Both `start` and `end` must point to the same allocated object and
/// must either be in bounds or at most one byte past the end of the
/// allocated object.
/// * Both `start` and `end` must be _derived from_ a pointer to the same
/// object.
/// * The distance between `start` and `end` must not overflow `isize`.
/// * The distance being in bounds must not rely on "wrapping around" the
/// address space.
///
/// Note that callers may pass a pair of pointers such that `start >= end`.
/// In that case, `None` will always be returned.
#[inline]
pub unsafe fn find_raw(
&self,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
if start >= end {
return None;
}
let confirm = |b| self.confirm(b);
let len = end.distance(start);
if len < USIZE_BYTES {
return generic::fwd_byte_by_byte(start, end, confirm);
}
// The start of the search may not be aligned to `*const usize`,
// so we do an unaligned load here.
let chunk = start.cast::<usize>().read_unaligned();
if self.has_needle(chunk) {
return generic::fwd_byte_by_byte(start, end, confirm);
}
// And now we start our search at a guaranteed aligned position.
// The first iteration of the loop below will overlap with the the
// unaligned chunk above in cases where the search starts at an
// unaligned offset, but that's okay as we're only here if that
// above didn't find a match.
let mut cur =
start.add(USIZE_BYTES - (start.as_usize() & USIZE_ALIGN));
debug_assert!(cur > start);
debug_assert!(end.sub(USIZE_BYTES) >= start);
while cur <= end.sub(USIZE_BYTES) {
debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES);
let chunk = cur.cast::<usize>().read();
if self.has_needle(chunk) {
break;
}
cur = cur.add(USIZE_BYTES);
}
generic::fwd_byte_by_byte(cur, end, confirm)
}
/// Like `rfind`, but accepts and returns raw pointers.
///
/// When a match is found, the pointer returned is guaranteed to be
/// `>= start` and `< end`.
///
/// This routine is useful if you're already using raw pointers and would
/// like to avoid converting back to a slice before executing a search.
///
/// # Safety
///
/// * Both `start` and `end` must be valid for reads.
/// * Both `start` and `end` must point to an initialized value.
/// * Both `start` and `end` must point to the same allocated object and
/// must either be in bounds or at most one byte past the end of the
/// allocated object.
/// * Both `start` and `end` must be _derived from_ a pointer to the same
/// object.
/// * The distance between `start` and `end` must not overflow `isize`.
/// * The distance being in bounds must not rely on "wrapping around" the
/// address space.
///
/// Note that callers may pass a pair of pointers such that `start >= end`.
/// In that case, `None` will always be returned.
#[inline]
pub unsafe fn rfind_raw(
&self,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
if start >= end {
return None;
}
let confirm = |b| self.confirm(b);
let len = end.distance(start);
if len < USIZE_BYTES {
return generic::rev_byte_by_byte(start, end, confirm);
}
let chunk = end.sub(USIZE_BYTES).cast::<usize>().read_unaligned();
if self.has_needle(chunk) {
return generic::rev_byte_by_byte(start, end, confirm);
}
let mut cur = end.sub(end.as_usize() & USIZE_ALIGN);
debug_assert!(start <= cur && cur <= end);
while cur >= start.add(USIZE_BYTES) {
debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES);
let chunk = cur.sub(USIZE_BYTES).cast::<usize>().read();
if self.has_needle(chunk) {
break;
}
cur = cur.sub(USIZE_BYTES);
}
generic::rev_byte_by_byte(start, cur, confirm)
}
/// Returns an iterator over all occurrences of one of the needle bytes in
/// the given haystack.
///
/// The iterator returned implements `DoubleEndedIterator`. This means it
/// can also be used to find occurrences in reverse order.
pub fn iter<'a, 'h>(&'a self, haystack: &'h [u8]) -> TwoIter<'a, 'h> {
TwoIter { searcher: self, it: generic::Iter::new(haystack) }
}
#[inline(always)]
fn has_needle(&self, chunk: usize) -> bool {
has_zero_byte(self.v1 ^ chunk) || has_zero_byte(self.v2 ^ chunk)
}
#[inline(always)]
fn confirm(&self, haystack_byte: u8) -> bool {
self.s1 == haystack_byte || self.s2 == haystack_byte
}
}
/// An iterator over all occurrences of two possible bytes in a haystack.
///
/// This iterator implements `DoubleEndedIterator`, which means it can also be
/// used to find occurrences in reverse order.
///
/// This iterator is created by the [`Two::iter`] method.
///
/// The lifetime parameters are as follows:
///
/// * `'a` refers to the lifetime of the underlying [`Two`] searcher.
/// * `'h` refers to the lifetime of the haystack being searched.
#[derive(Clone, Debug)]
pub struct TwoIter<'a, 'h> {
/// The underlying memchr searcher.
searcher: &'a Two,
/// Generic iterator implementation.
it: generic::Iter<'h>,
}
impl<'a, 'h> Iterator for TwoIter<'a, 'h> {
type Item = usize;
#[inline]
fn next(&mut self) -> Option<usize> {
// SAFETY: We rely on the generic iterator to provide valid start
// and end pointers, but we guarantee that any pointer returned by
// 'find_raw' falls within the bounds of the start and end pointer.
unsafe { self.it.next(|s, e| self.searcher.find_raw(s, e)) }
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.it.size_hint()
}
}
impl<'a, 'h> DoubleEndedIterator for TwoIter<'a, 'h> {
#[inline]
fn next_back(&mut self) -> Option<usize> {
// SAFETY: We rely on the generic iterator to provide valid start
// and end pointers, but we guarantee that any pointer returned by
// 'rfind_raw' falls within the bounds of the start and end pointer.
unsafe { self.it.next_back(|s, e| self.searcher.rfind_raw(s, e)) }
}
}
/// Finds all occurrences of three bytes in a haystack.
///
/// That is, this reports matches of one of three possible bytes. For example,
/// searching for `a`, `b` or `o` in `afoobar` would report matches at offsets
/// `0`, `2`, `3`, `4` and `5`.
#[derive(Clone, Copy, Debug)]
pub struct Three {
s1: u8,
s2: u8,
s3: u8,
v1: usize,
v2: usize,
v3: usize,
}
impl Three {
/// Create a new searcher that finds occurrences of the three needle bytes
/// given.
#[inline]
pub fn new(needle1: u8, needle2: u8, needle3: u8) -> Three {
Three {
s1: needle1,
s2: needle2,
s3: needle3,
v1: splat(needle1),
v2: splat(needle2),
v3: splat(needle3),
}
}
/// A test-only routine so that we can bundle a bunch of quickcheck
/// properties into a single macro. Basically, this provides a constructor
/// that makes it identical to most other memchr implementations, which
/// have fallible constructors.
#[cfg(test)]
pub(crate) fn try_new(
needle1: u8,
needle2: u8,
needle3: u8,
) -> Option<Three> {
Some(Three::new(needle1, needle2, needle3))
}
/// Return the first occurrence of one of the needle bytes in the given
/// haystack. If no such occurrence exists, then `None` is returned.
///
/// The occurrence is reported as an offset into `haystack`. Its maximum
/// value for a non-empty haystack is `haystack.len() - 1`.
#[inline]
pub fn find(&self, haystack: &[u8]) -> Option<usize> {
// SAFETY: `find_raw` guarantees that if a pointer is returned, it
// falls within the bounds of the start and end pointers.
unsafe {
generic::search_slice_with_raw(haystack, |s, e| {
self.find_raw(s, e)
})
}
}
/// Return the last occurrence of one of the needle bytes in the given
/// haystack. If no such occurrence exists, then `None` is returned.
///
/// The occurrence is reported as an offset into `haystack`. Its maximum
/// value for a non-empty haystack is `haystack.len() - 1`.
#[inline]
pub fn rfind(&self, haystack: &[u8]) -> Option<usize> {
// SAFETY: `find_raw` guarantees that if a pointer is returned, it
// falls within the bounds of the start and end pointers.
unsafe {
generic::search_slice_with_raw(haystack, |s, e| {
self.rfind_raw(s, e)
})
}
}
/// Like `find`, but accepts and returns raw pointers.
///
/// When a match is found, the pointer returned is guaranteed to be
/// `>= start` and `< end`.
///
/// This routine is useful if you're already using raw pointers and would
/// like to avoid converting back to a slice before executing a search.
///
/// # Safety
///
/// * Both `start` and `end` must be valid for reads.
/// * Both `start` and `end` must point to an initialized value.
/// * Both `start` and `end` must point to the same allocated object and
/// must either be in bounds or at most one byte past the end of the
/// allocated object.
/// * Both `start` and `end` must be _derived from_ a pointer to the same
/// object.
/// * The distance between `start` and `end` must not overflow `isize`.
/// * The distance being in bounds must not rely on "wrapping around" the
/// address space.
///
/// Note that callers may pass a pair of pointers such that `start >= end`.
/// In that case, `None` will always be returned.
#[inline]
pub unsafe fn find_raw(
&self,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
if start >= end {
return None;
}
let confirm = |b| self.confirm(b);
let len = end.distance(start);
if len < USIZE_BYTES {
return generic::fwd_byte_by_byte(start, end, confirm);
}
// The start of the search may not be aligned to `*const usize`,
// so we do an unaligned load here.
let chunk = start.cast::<usize>().read_unaligned();
if self.has_needle(chunk) {
return generic::fwd_byte_by_byte(start, end, confirm);
}
// And now we start our search at a guaranteed aligned position.
// The first iteration of the loop below will overlap with the the
// unaligned chunk above in cases where the search starts at an
// unaligned offset, but that's okay as we're only here if that
// above didn't find a match.
let mut cur =
start.add(USIZE_BYTES - (start.as_usize() & USIZE_ALIGN));
debug_assert!(cur > start);
debug_assert!(end.sub(USIZE_BYTES) >= start);
while cur <= end.sub(USIZE_BYTES) {
debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES);
let chunk = cur.cast::<usize>().read();
if self.has_needle(chunk) {
break;
}
cur = cur.add(USIZE_BYTES);
}
generic::fwd_byte_by_byte(cur, end, confirm)
}
/// Like `rfind`, but accepts and returns raw pointers.
///
/// When a match is found, the pointer returned is guaranteed to be
/// `>= start` and `< end`.
///
/// This routine is useful if you're already using raw pointers and would
/// like to avoid converting back to a slice before executing a search.
///
/// # Safety
///
/// * Both `start` and `end` must be valid for reads.
/// * Both `start` and `end` must point to an initialized value.
/// * Both `start` and `end` must point to the same allocated object and
/// must either be in bounds or at most one byte past the end of the
/// allocated object.
/// * Both `start` and `end` must be _derived from_ a pointer to the same
/// object.
/// * The distance between `start` and `end` must not overflow `isize`.
/// * The distance being in bounds must not rely on "wrapping around" the
/// address space.
///
/// Note that callers may pass a pair of pointers such that `start >= end`.
/// In that case, `None` will always be returned.
#[inline]
pub unsafe fn rfind_raw(
&self,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
if start >= end {
return None;
}
let confirm = |b| self.confirm(b);
let len = end.distance(start);
if len < USIZE_BYTES {
return generic::rev_byte_by_byte(start, end, confirm);
}
let chunk = end.sub(USIZE_BYTES).cast::<usize>().read_unaligned();
if self.has_needle(chunk) {
return generic::rev_byte_by_byte(start, end, confirm);
}
let mut cur = end.sub(end.as_usize() & USIZE_ALIGN);
debug_assert!(start <= cur && cur <= end);
while cur >= start.add(USIZE_BYTES) {
debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES);
let chunk = cur.sub(USIZE_BYTES).cast::<usize>().read();
if self.has_needle(chunk) {
break;
}
cur = cur.sub(USIZE_BYTES);
}
generic::rev_byte_by_byte(start, cur, confirm)
}
/// Returns an iterator over all occurrences of one of the needle bytes in
/// the given haystack.
///
/// The iterator returned implements `DoubleEndedIterator`. This means it
/// can also be used to find occurrences in reverse order.
pub fn iter<'a, 'h>(&'a self, haystack: &'h [u8]) -> ThreeIter<'a, 'h> {
ThreeIter { searcher: self, it: generic::Iter::new(haystack) }
}
#[inline(always)]
fn has_needle(&self, chunk: usize) -> bool {
has_zero_byte(self.v1 ^ chunk)
|| has_zero_byte(self.v2 ^ chunk)
|| has_zero_byte(self.v3 ^ chunk)
}
#[inline(always)]
fn confirm(&self, haystack_byte: u8) -> bool {
self.s1 == haystack_byte
|| self.s2 == haystack_byte
|| self.s3 == haystack_byte
}
}
/// An iterator over all occurrences of three possible bytes in a haystack.
///
/// This iterator implements `DoubleEndedIterator`, which means it can also be
/// used to find occurrences in reverse order.
///
/// This iterator is created by the [`Three::iter`] method.
///
/// The lifetime parameters are as follows:
///
/// * `'a` refers to the lifetime of the underlying [`Three`] searcher.
/// * `'h` refers to the lifetime of the haystack being searched.
#[derive(Clone, Debug)]
pub struct ThreeIter<'a, 'h> {
/// The underlying memchr searcher.
searcher: &'a Three,
/// Generic iterator implementation.
it: generic::Iter<'h>,
}
impl<'a, 'h> Iterator for ThreeIter<'a, 'h> {
type Item = usize;
#[inline]
fn next(&mut self) -> Option<usize> {
// SAFETY: We rely on the generic iterator to provide valid start
// and end pointers, but we guarantee that any pointer returned by
// 'find_raw' falls within the bounds of the start and end pointer.
unsafe { self.it.next(|s, e| self.searcher.find_raw(s, e)) }
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.it.size_hint()
}
}
impl<'a, 'h> DoubleEndedIterator for ThreeIter<'a, 'h> {
#[inline]
fn next_back(&mut self) -> Option<usize> {
// SAFETY: We rely on the generic iterator to provide valid start
// and end pointers, but we guarantee that any pointer returned by
// 'rfind_raw' falls within the bounds of the start and end pointer.
unsafe { self.it.next_back(|s, e| self.searcher.rfind_raw(s, e)) }
}
}
/// Return `true` if `x` contains any zero byte.
///
/// That is, this routine treats `x` as a register of 8-bit lanes and returns
/// true when any of those lanes is `0`.
///
/// From "Matters Computational" by J. Arndt.
#[inline(always)]
fn has_zero_byte(x: usize) -> bool {
// "The idea is to subtract one from each of the bytes and then look for
// bytes where the borrow propagated all the way to the most significant
// bit."
const LO: usize = splat(0x01);
const HI: usize = splat(0x80);
(x.wrapping_sub(LO) & !x & HI) != 0
}
/// Repeat the given byte into a word size number. That is, every 8 bits
/// is equivalent to the given byte. For example, if `b` is `\x4E` or
/// `01001110` in binary, then the returned value on a 32-bit system would be:
/// `01001110_01001110_01001110_01001110`.
#[inline(always)]
const fn splat(b: u8) -> usize {
// TODO: use `usize::from` once it can be used in const context.
(b as usize) * (usize::MAX / 255)
}
#[cfg(test)]
mod tests {
use super::*;
define_memchr_quickcheck!(super, try_new);
#[test]
fn forward_one() {
crate::tests::memchr::Runner::new(1).forward_iter(
|haystack, needles| {
Some(One::new(needles[0]).iter(haystack).collect())
},
)
}
#[test]
fn reverse_one() {
crate::tests::memchr::Runner::new(1).reverse_iter(
|haystack, needles| {
Some(One::new(needles[0]).iter(haystack).rev().collect())
},
)
}
#[test]
fn count_one() {
crate::tests::memchr::Runner::new(1).count_iter(|haystack, needles| {
Some(One::new(needles[0]).iter(haystack).count())
})
}
#[test]
fn forward_two() {
crate::tests::memchr::Runner::new(2).forward_iter(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
Some(Two::new(n1, n2).iter(haystack).collect())
},
)
}
#[test]
fn reverse_two() {
crate::tests::memchr::Runner::new(2).reverse_iter(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
Some(Two::new(n1, n2).iter(haystack).rev().collect())
},
)
}
#[test]
fn forward_three() {
crate::tests::memchr::Runner::new(3).forward_iter(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
let n3 = needles.get(2).copied()?;
Some(Three::new(n1, n2, n3).iter(haystack).collect())
},
)
}
#[test]
fn reverse_three() {
crate::tests::memchr::Runner::new(3).reverse_iter(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
let n3 = needles.get(2).copied()?;
Some(Three::new(n1, n2, n3).iter(haystack).rev().collect())
},
)
}
// This was found by quickcheck in the course of refactoring this crate
// after memchr 2.5.0.
#[test]
fn regression_double_ended_iterator() {
let finder = One::new(b'a');
let haystack = "a";
let mut it = finder.iter(haystack.as_bytes());
assert_eq!(Some(0), it.next());
assert_eq!(None, it.next_back());
}
// This regression test was caught by ripgrep's test suite on i686 when
// upgrading to memchr 2.6. Namely, something about the \x0B bytes here
// screws with the SWAR counting approach I was using. This regression test
// prompted me to remove the SWAR counting approach and just replace it
// with a byte-at-a-time loop.
#[test]
fn regression_count_new_lines() {
let haystack = "01234567\x0b\n\x0b\n\x0b\n\x0b\nx";
let count = One::new(b'\n').count(haystack.as_bytes());
assert_eq!(4, count);
}
}

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vendor/memchr/src/arch/all/mod.rs vendored Normal file
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@ -0,0 +1,234 @@
/*!
Contains architecture independent routines.
These routines are often used as a "fallback" implementation when the more
specialized architecture dependent routines are unavailable.
*/
pub mod memchr;
pub mod packedpair;
pub mod rabinkarp;
#[cfg(feature = "alloc")]
pub mod shiftor;
pub mod twoway;
/// Returns true if and only if `needle` is a prefix of `haystack`.
///
/// This uses a latency optimized variant of `memcmp` internally which *might*
/// make this faster for very short strings.
///
/// # Inlining
///
/// This routine is marked `inline(always)`. If you want to call this function
/// in a way that is not always inlined, you'll need to wrap a call to it in
/// another function that is marked as `inline(never)` or just `inline`.
#[inline(always)]
pub fn is_prefix(haystack: &[u8], needle: &[u8]) -> bool {
needle.len() <= haystack.len()
&& is_equal(&haystack[..needle.len()], needle)
}
/// Returns true if and only if `needle` is a suffix of `haystack`.
///
/// This uses a latency optimized variant of `memcmp` internally which *might*
/// make this faster for very short strings.
///
/// # Inlining
///
/// This routine is marked `inline(always)`. If you want to call this function
/// in a way that is not always inlined, you'll need to wrap a call to it in
/// another function that is marked as `inline(never)` or just `inline`.
#[inline(always)]
pub fn is_suffix(haystack: &[u8], needle: &[u8]) -> bool {
needle.len() <= haystack.len()
&& is_equal(&haystack[haystack.len() - needle.len()..], needle)
}
/// Compare corresponding bytes in `x` and `y` for equality.
///
/// That is, this returns true if and only if `x.len() == y.len()` and
/// `x[i] == y[i]` for all `0 <= i < x.len()`.
///
/// # Inlining
///
/// This routine is marked `inline(always)`. If you want to call this function
/// in a way that is not always inlined, you'll need to wrap a call to it in
/// another function that is marked as `inline(never)` or just `inline`.
///
/// # Motivation
///
/// Why not use slice equality instead? Well, slice equality usually results in
/// a call out to the current platform's `libc` which might not be inlineable
/// or have other overhead. This routine isn't guaranteed to be a win, but it
/// might be in some cases.
#[inline(always)]
pub fn is_equal(x: &[u8], y: &[u8]) -> bool {
if x.len() != y.len() {
return false;
}
// SAFETY: Our pointers are derived directly from borrowed slices which
// uphold all of our safety guarantees except for length. We account for
// length with the check above.
unsafe { is_equal_raw(x.as_ptr(), y.as_ptr(), x.len()) }
}
/// Compare `n` bytes at the given pointers for equality.
///
/// This returns true if and only if `*x.add(i) == *y.add(i)` for all
/// `0 <= i < n`.
///
/// # Inlining
///
/// This routine is marked `inline(always)`. If you want to call this function
/// in a way that is not always inlined, you'll need to wrap a call to it in
/// another function that is marked as `inline(never)` or just `inline`.
///
/// # Motivation
///
/// Why not use slice equality instead? Well, slice equality usually results in
/// a call out to the current platform's `libc` which might not be inlineable
/// or have other overhead. This routine isn't guaranteed to be a win, but it
/// might be in some cases.
///
/// # Safety
///
/// * Both `x` and `y` must be valid for reads of up to `n` bytes.
/// * Both `x` and `y` must point to an initialized value.
/// * Both `x` and `y` must each point to an allocated object and
/// must either be in bounds or at most one byte past the end of the
/// allocated object. `x` and `y` do not need to point to the same allocated
/// object, but they may.
/// * Both `x` and `y` must be _derived from_ a pointer to their respective
/// allocated objects.
/// * The distance between `x` and `x+n` must not overflow `isize`. Similarly
/// for `y` and `y+n`.
/// * The distance being in bounds must not rely on "wrapping around" the
/// address space.
#[inline(always)]
pub unsafe fn is_equal_raw(
mut x: *const u8,
mut y: *const u8,
mut n: usize,
) -> bool {
// When we have 4 or more bytes to compare, then proceed in chunks of 4 at
// a time using unaligned loads.
//
// Also, why do 4 byte loads instead of, say, 8 byte loads? The reason is
// that this particular version of memcmp is likely to be called with tiny
// needles. That means that if we do 8 byte loads, then a higher proportion
// of memcmp calls will use the slower variant above. With that said, this
// is a hypothesis and is only loosely supported by benchmarks. There's
// likely some improvement that could be made here. The main thing here
// though is to optimize for latency, not throughput.
// SAFETY: The caller is responsible for ensuring the pointers we get are
// valid and readable for at least `n` bytes. We also do unaligned loads,
// so there's no need to ensure we're aligned. (This is justified by this
// routine being specifically for short strings.)
while n >= 4 {
let vx = x.cast::<u32>().read_unaligned();
let vy = y.cast::<u32>().read_unaligned();
if vx != vy {
return false;
}
x = x.add(4);
y = y.add(4);
n -= 4;
}
// If we don't have enough bytes to do 4-byte at a time loads, then
// do partial loads. Note that I used to have a byte-at-a-time
// loop here and that turned out to be quite a bit slower for the
// memmem/pathological/defeat-simple-vector-alphabet benchmark.
if n >= 2 {
let vx = x.cast::<u16>().read_unaligned();
let vy = y.cast::<u16>().read_unaligned();
if vx != vy {
return false;
}
x = x.add(2);
y = y.add(2);
n -= 2;
}
if n > 0 {
if x.read() != y.read() {
return false;
}
}
true
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn equals_different_lengths() {
assert!(!is_equal(b"", b"a"));
assert!(!is_equal(b"a", b""));
assert!(!is_equal(b"ab", b"a"));
assert!(!is_equal(b"a", b"ab"));
}
#[test]
fn equals_mismatch() {
let one_mismatch = [
(&b"a"[..], &b"x"[..]),
(&b"ab"[..], &b"ax"[..]),
(&b"abc"[..], &b"abx"[..]),
(&b"abcd"[..], &b"abcx"[..]),
(&b"abcde"[..], &b"abcdx"[..]),
(&b"abcdef"[..], &b"abcdex"[..]),
(&b"abcdefg"[..], &b"abcdefx"[..]),
(&b"abcdefgh"[..], &b"abcdefgx"[..]),
(&b"abcdefghi"[..], &b"abcdefghx"[..]),
(&b"abcdefghij"[..], &b"abcdefghix"[..]),
(&b"abcdefghijk"[..], &b"abcdefghijx"[..]),
(&b"abcdefghijkl"[..], &b"abcdefghijkx"[..]),
(&b"abcdefghijklm"[..], &b"abcdefghijklx"[..]),
(&b"abcdefghijklmn"[..], &b"abcdefghijklmx"[..]),
];
for (x, y) in one_mismatch {
assert_eq!(x.len(), y.len(), "lengths should match");
assert!(!is_equal(x, y));
assert!(!is_equal(y, x));
}
}
#[test]
fn equals_yes() {
assert!(is_equal(b"", b""));
assert!(is_equal(b"a", b"a"));
assert!(is_equal(b"ab", b"ab"));
assert!(is_equal(b"abc", b"abc"));
assert!(is_equal(b"abcd", b"abcd"));
assert!(is_equal(b"abcde", b"abcde"));
assert!(is_equal(b"abcdef", b"abcdef"));
assert!(is_equal(b"abcdefg", b"abcdefg"));
assert!(is_equal(b"abcdefgh", b"abcdefgh"));
assert!(is_equal(b"abcdefghi", b"abcdefghi"));
}
#[test]
fn prefix() {
assert!(is_prefix(b"", b""));
assert!(is_prefix(b"a", b""));
assert!(is_prefix(b"ab", b""));
assert!(is_prefix(b"foo", b"foo"));
assert!(is_prefix(b"foobar", b"foo"));
assert!(!is_prefix(b"foo", b"fob"));
assert!(!is_prefix(b"foobar", b"fob"));
}
#[test]
fn suffix() {
assert!(is_suffix(b"", b""));
assert!(is_suffix(b"a", b""));
assert!(is_suffix(b"ab", b""));
assert!(is_suffix(b"foo", b"foo"));
assert!(is_suffix(b"foobar", b"bar"));
assert!(!is_suffix(b"foo", b"goo"));
assert!(!is_suffix(b"foobar", b"gar"));
}
}

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pub(crate) const RANK: [u8; 256] = [
55, // '\x00'
52, // '\x01'
51, // '\x02'
50, // '\x03'
49, // '\x04'
48, // '\x05'
47, // '\x06'
46, // '\x07'
45, // '\x08'
103, // '\t'
242, // '\n'
66, // '\x0b'
67, // '\x0c'
229, // '\r'
44, // '\x0e'
43, // '\x0f'
42, // '\x10'
41, // '\x11'
40, // '\x12'
39, // '\x13'
38, // '\x14'
37, // '\x15'
36, // '\x16'
35, // '\x17'
34, // '\x18'
33, // '\x19'
56, // '\x1a'
32, // '\x1b'
31, // '\x1c'
30, // '\x1d'
29, // '\x1e'
28, // '\x1f'
255, // ' '
148, // '!'
164, // '"'
149, // '#'
136, // '$'
160, // '%'
155, // '&'
173, // "'"
221, // '('
222, // ')'
134, // '*'
122, // '+'
232, // ','
202, // '-'
215, // '.'
224, // '/'
208, // '0'
220, // '1'
204, // '2'
187, // '3'
183, // '4'
179, // '5'
177, // '6'
168, // '7'
178, // '8'
200, // '9'
226, // ':'
195, // ';'
154, // '<'
184, // '='
174, // '>'
126, // '?'
120, // '@'
191, // 'A'
157, // 'B'
194, // 'C'
170, // 'D'
189, // 'E'
162, // 'F'
161, // 'G'
150, // 'H'
193, // 'I'
142, // 'J'
137, // 'K'
171, // 'L'
176, // 'M'
185, // 'N'
167, // 'O'
186, // 'P'
112, // 'Q'
175, // 'R'
192, // 'S'
188, // 'T'
156, // 'U'
140, // 'V'
143, // 'W'
123, // 'X'
133, // 'Y'
128, // 'Z'
147, // '['
138, // '\\'
146, // ']'
114, // '^'
223, // '_'
151, // '`'
249, // 'a'
216, // 'b'
238, // 'c'
236, // 'd'
253, // 'e'
227, // 'f'
218, // 'g'
230, // 'h'
247, // 'i'
135, // 'j'
180, // 'k'
241, // 'l'
233, // 'm'
246, // 'n'
244, // 'o'
231, // 'p'
139, // 'q'
245, // 'r'
243, // 's'
251, // 't'
235, // 'u'
201, // 'v'
196, // 'w'
240, // 'x'
214, // 'y'
152, // 'z'
182, // '{'
205, // '|'
181, // '}'
127, // '~'
27, // '\x7f'
212, // '\x80'
211, // '\x81'
210, // '\x82'
213, // '\x83'
228, // '\x84'
197, // '\x85'
169, // '\x86'
159, // '\x87'
131, // '\x88'
172, // '\x89'
105, // '\x8a'
80, // '\x8b'
98, // '\x8c'
96, // '\x8d'
97, // '\x8e'
81, // '\x8f'
207, // '\x90'
145, // '\x91'
116, // '\x92'
115, // '\x93'
144, // '\x94'
130, // '\x95'
153, // '\x96'
121, // '\x97'
107, // '\x98'
132, // '\x99'
109, // '\x9a'
110, // '\x9b'
124, // '\x9c'
111, // '\x9d'
82, // '\x9e'
108, // '\x9f'
118, // '\xa0'
141, // '¡'
113, // '¢'
129, // '£'
119, // '¤'
125, // '¥'
165, // '¦'
117, // '§'
92, // '¨'
106, // '©'
83, // 'ª'
72, // '«'
99, // '¬'
93, // '\xad'
65, // '®'
79, // '¯'
166, // '°'
237, // '±'
163, // '²'
199, // '³'
190, // '´'
225, // 'µ'
209, // '¶'
203, // '·'
198, // '¸'
217, // '¹'
219, // 'º'
206, // '»'
234, // '¼'
248, // '½'
158, // '¾'
239, // '¿'
255, // 'À'
255, // 'Á'
255, // 'Â'
255, // 'Ã'
255, // 'Ä'
255, // 'Å'
255, // 'Æ'
255, // 'Ç'
255, // 'È'
255, // 'É'
255, // 'Ê'
255, // 'Ë'
255, // 'Ì'
255, // 'Í'
255, // 'Î'
255, // 'Ï'
255, // 'Ð'
255, // 'Ñ'
255, // 'Ò'
255, // 'Ó'
255, // 'Ô'
255, // 'Õ'
255, // 'Ö'
255, // '×'
255, // 'Ø'
255, // 'Ù'
255, // 'Ú'
255, // 'Û'
255, // 'Ü'
255, // 'Ý'
255, // 'Þ'
255, // 'ß'
255, // 'à'
255, // 'á'
255, // 'â'
255, // 'ã'
255, // 'ä'
255, // 'å'
255, // 'æ'
255, // 'ç'
255, // 'è'
255, // 'é'
255, // 'ê'
255, // 'ë'
255, // 'ì'
255, // 'í'
255, // 'î'
255, // 'ï'
255, // 'ð'
255, // 'ñ'
255, // 'ò'
255, // 'ó'
255, // 'ô'
255, // 'õ'
255, // 'ö'
255, // '÷'
255, // 'ø'
255, // 'ù'
255, // 'ú'
255, // 'û'
255, // 'ü'
255, // 'ý'
255, // 'þ'
255, // 'ÿ'
];

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/*!
Provides an architecture independent implementation of the "packed pair"
algorithm.
The "packed pair" algorithm is based on the [generic SIMD] algorithm. The main
difference is that it (by default) uses a background distribution of byte
frequencies to heuristically select the pair of bytes to search for. Note that
this module provides an architecture independent version that doesn't do as
good of a job keeping the search for candidates inside a SIMD hot path. It
however can be good enough in many circumstances.
[generic SIMD]: http://0x80.pl/articles/simd-strfind.html#first-and-last
*/
use crate::memchr;
mod default_rank;
/// An architecture independent "packed pair" finder.
///
/// This finder picks two bytes that it believes have high predictive power for
/// indicating an overall match of a needle. At search time, it reports offsets
/// where the needle could match based on whether the pair of bytes it chose
/// match.
///
/// This is architecture independent because it utilizes `memchr` to find the
/// occurrence of one of the bytes in the pair, and then checks whether the
/// second byte matches. If it does, in the case of [`Finder::find_prefilter`],
/// the location at which the needle could match is returned.
///
/// It is generally preferred to use architecture specific routines for a
/// "packed pair" prefilter, but this can be a useful fallback when the
/// architecture independent routines are unavailable.
#[derive(Clone, Copy, Debug)]
pub struct Finder {
pair: Pair,
byte1: u8,
byte2: u8,
}
impl Finder {
/// Create a new prefilter that reports possible locations where the given
/// needle matches.
#[inline]
pub fn new(needle: &[u8]) -> Option<Finder> {
Finder::with_pair(needle, Pair::new(needle)?)
}
/// Create a new prefilter using the pair given.
///
/// If the prefilter could not be constructed, then `None` is returned.
///
/// This constructor permits callers to control precisely which pair of
/// bytes is used as a predicate.
#[inline]
pub fn with_pair(needle: &[u8], pair: Pair) -> Option<Finder> {
let byte1 = needle[usize::from(pair.index1())];
let byte2 = needle[usize::from(pair.index2())];
// Currently this can never fail so we could just return a Finder,
// but it's conceivable this could change.
Some(Finder { pair, byte1, byte2 })
}
/// Run this finder on the given haystack as a prefilter.
///
/// If a candidate match is found, then an offset where the needle *could*
/// begin in the haystack is returned.
#[inline]
pub fn find_prefilter(&self, haystack: &[u8]) -> Option<usize> {
let mut i = 0;
let index1 = usize::from(self.pair.index1());
let index2 = usize::from(self.pair.index2());
loop {
// Use a fast vectorized implementation to skip to the next
// occurrence of the rarest byte (heuristically chosen) in the
// needle.
i += memchr(self.byte1, &haystack[i..])?;
let found = i;
i += 1;
// If we can't align our first byte match with the haystack, then a
// match is impossible.
let aligned1 = match found.checked_sub(index1) {
None => continue,
Some(aligned1) => aligned1,
};
// Now align the second byte match with the haystack. A mismatch
// means that a match is impossible.
let aligned2 = match aligned1.checked_add(index2) {
None => continue,
Some(aligned_index2) => aligned_index2,
};
if haystack.get(aligned2).map_or(true, |&b| b != self.byte2) {
continue;
}
// We've done what we can. There might be a match here.
return Some(aligned1);
}
}
/// Returns the pair of offsets (into the needle) used to check as a
/// predicate before confirming whether a needle exists at a particular
/// position.
#[inline]
pub fn pair(&self) -> &Pair {
&self.pair
}
}
/// A pair of byte offsets into a needle to use as a predicate.
///
/// This pair is used as a predicate to quickly filter out positions in a
/// haystack in which a needle cannot match. In some cases, this pair can even
/// be used in vector algorithms such that the vector algorithm only switches
/// over to scalar code once this pair has been found.
///
/// A pair of offsets can be used in both substring search implementations and
/// in prefilters. The former will report matches of a needle in a haystack
/// where as the latter will only report possible matches of a needle.
///
/// The offsets are limited each to a maximum of 255 to keep memory usage low.
/// Moreover, it's rarely advantageous to create a predicate using offsets
/// greater than 255 anyway.
///
/// The only guarantee enforced on the pair of offsets is that they are not
/// equivalent. It is not necessarily the case that `index1 < index2` for
/// example. By convention, `index1` corresponds to the byte in the needle
/// that is believed to be most the predictive. Note also that because of the
/// requirement that the indices be both valid for the needle used to build
/// the pair and not equal, it follows that a pair can only be constructed for
/// needles with length at least 2.
#[derive(Clone, Copy, Debug)]
pub struct Pair {
index1: u8,
index2: u8,
}
impl Pair {
/// Create a new pair of offsets from the given needle.
///
/// If a pair could not be created (for example, if the needle is too
/// short), then `None` is returned.
///
/// This chooses the pair in the needle that is believed to be as
/// predictive of an overall match of the needle as possible.
#[inline]
pub fn new(needle: &[u8]) -> Option<Pair> {
Pair::with_ranker(needle, DefaultFrequencyRank)
}
/// Create a new pair of offsets from the given needle and ranker.
///
/// This permits the caller to choose a background frequency distribution
/// with which bytes are selected. The idea is to select a pair of bytes
/// that is believed to strongly predict a match in the haystack. This
/// usually means selecting bytes that occur rarely in a haystack.
///
/// If a pair could not be created (for example, if the needle is too
/// short), then `None` is returned.
#[inline]
pub fn with_ranker<R: HeuristicFrequencyRank>(
needle: &[u8],
ranker: R,
) -> Option<Pair> {
if needle.len() <= 1 {
return None;
}
// Find the rarest two bytes. We make them distinct indices by
// construction. (The actual byte value may be the same in degenerate
// cases, but that's OK.)
let (mut rare1, mut index1) = (needle[0], 0);
let (mut rare2, mut index2) = (needle[1], 1);
if ranker.rank(rare2) < ranker.rank(rare1) {
core::mem::swap(&mut rare1, &mut rare2);
core::mem::swap(&mut index1, &mut index2);
}
let max = usize::from(core::u8::MAX);
for (i, &b) in needle.iter().enumerate().take(max).skip(2) {
if ranker.rank(b) < ranker.rank(rare1) {
rare2 = rare1;
index2 = index1;
rare1 = b;
index1 = u8::try_from(i).unwrap();
} else if b != rare1 && ranker.rank(b) < ranker.rank(rare2) {
rare2 = b;
index2 = u8::try_from(i).unwrap();
}
}
// While not strictly required for how a Pair is normally used, we
// really don't want these to be equivalent. If they were, it would
// reduce the effectiveness of candidate searching using these rare
// bytes by increasing the rate of false positives.
assert_ne!(index1, index2);
Some(Pair { index1, index2 })
}
/// Create a new pair using the offsets given for the needle given.
///
/// This bypasses any sort of heuristic process for choosing the offsets
/// and permits the caller to choose the offsets themselves.
///
/// Indices are limited to valid `u8` values so that a `Pair` uses less
/// memory. It is not possible to create a `Pair` with offsets bigger than
/// `u8::MAX`. It's likely that such a thing is not needed, but if it is,
/// it's suggested to build your own bespoke algorithm because you're
/// likely working on a very niche case. (File an issue if this suggestion
/// does not make sense to you.)
///
/// If a pair could not be created (for example, if the needle is too
/// short), then `None` is returned.
#[inline]
pub fn with_indices(
needle: &[u8],
index1: u8,
index2: u8,
) -> Option<Pair> {
// While not strictly required for how a Pair is normally used, we
// really don't want these to be equivalent. If they were, it would
// reduce the effectiveness of candidate searching using these rare
// bytes by increasing the rate of false positives.
if index1 == index2 {
return None;
}
// Similarly, invalid indices means the Pair is invalid too.
if usize::from(index1) >= needle.len() {
return None;
}
if usize::from(index2) >= needle.len() {
return None;
}
Some(Pair { index1, index2 })
}
/// Returns the first offset of the pair.
#[inline]
pub fn index1(&self) -> u8 {
self.index1
}
/// Returns the second offset of the pair.
#[inline]
pub fn index2(&self) -> u8 {
self.index2
}
}
/// This trait allows the user to customize the heuristic used to determine the
/// relative frequency of a given byte in the dataset being searched.
///
/// The use of this trait can have a dramatic impact on performance depending
/// on the type of data being searched. The details of why are explained in the
/// docs of [`crate::memmem::Prefilter`]. To summarize, the core algorithm uses
/// a prefilter to quickly identify candidate matches that are later verified
/// more slowly. This prefilter is implemented in terms of trying to find
/// `rare` bytes at specific offsets that will occur less frequently in the
/// dataset. While the concept of a `rare` byte is similar for most datasets,
/// there are some specific datasets (like binary executables) that have
/// dramatically different byte distributions. For these datasets customizing
/// the byte frequency heuristic can have a massive impact on performance, and
/// might even need to be done at runtime.
///
/// The default implementation of `HeuristicFrequencyRank` reads from the
/// static frequency table defined in `src/memmem/byte_frequencies.rs`. This
/// is optimal for most inputs, so if you are unsure of the impact of using a
/// custom `HeuristicFrequencyRank` you should probably just use the default.
///
/// # Example
///
/// ```
/// use memchr::{
/// arch::all::packedpair::HeuristicFrequencyRank,
/// memmem::FinderBuilder,
/// };
///
/// /// A byte-frequency table that is good for scanning binary executables.
/// struct Binary;
///
/// impl HeuristicFrequencyRank for Binary {
/// fn rank(&self, byte: u8) -> u8 {
/// const TABLE: [u8; 256] = [
/// 255, 128, 61, 43, 50, 41, 27, 28, 57, 15, 21, 13, 24, 17, 17,
/// 89, 58, 16, 11, 7, 14, 23, 7, 6, 24, 9, 6, 5, 9, 4, 7, 16,
/// 68, 11, 9, 6, 88, 7, 4, 4, 23, 9, 4, 8, 8, 5, 10, 4, 30, 11,
/// 9, 24, 11, 5, 5, 5, 19, 11, 6, 17, 9, 9, 6, 8,
/// 48, 58, 11, 14, 53, 40, 9, 9, 254, 35, 3, 6, 52, 23, 6, 6, 27,
/// 4, 7, 11, 14, 13, 10, 11, 11, 5, 2, 10, 16, 12, 6, 19,
/// 19, 20, 5, 14, 16, 31, 19, 7, 14, 20, 4, 4, 19, 8, 18, 20, 24,
/// 1, 25, 19, 58, 29, 10, 5, 15, 20, 2, 2, 9, 4, 3, 5,
/// 51, 11, 4, 53, 23, 39, 6, 4, 13, 81, 4, 186, 5, 67, 3, 2, 15,
/// 0, 0, 1, 3, 2, 0, 0, 5, 0, 0, 0, 2, 0, 0, 0,
/// 12, 2, 1, 1, 3, 1, 1, 1, 6, 1, 2, 1, 3, 1, 1, 2, 9, 1, 1, 0,
/// 2, 2, 4, 4, 11, 6, 7, 3, 6, 9, 4, 5,
/// 46, 18, 8, 18, 17, 3, 8, 20, 16, 10, 3, 7, 175, 4, 6, 7, 13,
/// 3, 7, 3, 3, 1, 3, 3, 10, 3, 1, 5, 2, 0, 1, 2,
/// 16, 3, 5, 1, 6, 1, 1, 2, 58, 20, 3, 14, 12, 2, 1, 3, 16, 3, 5,
/// 8, 3, 1, 8, 6, 17, 6, 5, 3, 8, 6, 13, 175,
/// ];
/// TABLE[byte as usize]
/// }
/// }
/// // Create a new finder with the custom heuristic.
/// let finder = FinderBuilder::new()
/// .build_forward_with_ranker(Binary, b"\x00\x00\xdd\xdd");
/// // Find needle with custom heuristic.
/// assert!(finder.find(b"\x00\x00\x00\xdd\xdd").is_some());
/// ```
pub trait HeuristicFrequencyRank {
/// Return the heuristic frequency rank of the given byte. A lower rank
/// means the byte is believed to occur less frequently in the haystack.
///
/// Some uses of this heuristic may treat arbitrary absolute rank values as
/// significant. For example, an implementation detail in this crate may
/// determine that heuristic prefilters are inappropriate if every byte in
/// the needle has a "high" rank.
fn rank(&self, byte: u8) -> u8;
}
/// The default byte frequency heuristic that is good for most haystacks.
pub(crate) struct DefaultFrequencyRank;
impl HeuristicFrequencyRank for DefaultFrequencyRank {
fn rank(&self, byte: u8) -> u8 {
self::default_rank::RANK[usize::from(byte)]
}
}
/// This permits passing any implementation of `HeuristicFrequencyRank` as a
/// borrowed version of itself.
impl<'a, R> HeuristicFrequencyRank for &'a R
where
R: HeuristicFrequencyRank,
{
fn rank(&self, byte: u8) -> u8 {
(**self).rank(byte)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn forward_packedpair() {
fn find(
haystack: &[u8],
needle: &[u8],
_index1: u8,
_index2: u8,
) -> Option<Option<usize>> {
// We ignore the index positions requested since it winds up making
// this test too slow overall.
let f = Finder::new(needle)?;
Some(f.find_prefilter(haystack))
}
crate::tests::packedpair::Runner::new().fwd(find).run()
}
}

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/*!
An implementation of the [Rabin-Karp substring search algorithm][rabinkarp].
Rabin-Karp works by creating a hash of the needle provided and then computing
a rolling hash for each needle sized window in the haystack. When the rolling
hash matches the hash of the needle, a byte-wise comparison is done to check
if a match exists. The worst case time complexity of Rabin-Karp is `O(m *
n)` where `m ~ len(needle)` and `n ~ len(haystack)`. Its worst case space
complexity is constant.
The main utility of Rabin-Karp is that the searcher can be constructed very
quickly with very little memory. This makes it especially useful when searching
for small needles in small haystacks, as it might finish its search before a
beefier algorithm (like Two-Way) even starts.
[rabinkarp]: https://en.wikipedia.org/wiki/Rabin%E2%80%93Karp_algorithm
*/
/*
(This was the comment I wrote for this module originally when it was not
exposed. The comment still looks useful, but it's a bit in the weeds, so it's
not public itself.)
This module implements the classical Rabin-Karp substring search algorithm,
with no extra frills. While its use would seem to break our time complexity
guarantee of O(m+n) (RK's time complexity is O(mn)), we are careful to only
ever use RK on a constant subset of haystacks. The main point here is that
RK has good latency properties for small needles/haystacks. It's very quick
to compute a needle hash and zip through the haystack when compared to
initializing Two-Way, for example. And this is especially useful for cases
where the haystack is just too short for vector instructions to do much good.
The hashing function used here is the same one recommended by ESMAJ.
Another choice instead of Rabin-Karp would be Shift-Or. But its latency
isn't quite as good since its preprocessing time is a bit more expensive
(both in practice and in theory). However, perhaps Shift-Or has a place
somewhere else for short patterns. I think the main problem is that it
requires space proportional to the alphabet and the needle. If we, for
example, supported needles up to length 16, then the total table size would be
len(alphabet)*size_of::<u16>()==512 bytes. Which isn't exactly small, and it's
probably bad to put that on the stack. So ideally, we'd throw it on the heap,
but we'd really like to write as much code without using alloc/std as possible.
But maybe it's worth the special casing. It's a TODO to benchmark.
Wikipedia has a decent explanation, if a bit heavy on the theory:
https://en.wikipedia.org/wiki/Rabin%E2%80%93Karp_algorithm
But ESMAJ provides something a bit more concrete:
http://www-igm.univ-mlv.fr/~lecroq/string/node5.html
Finally, aho-corasick uses Rabin-Karp for multiple pattern match in some cases:
https://github.com/BurntSushi/aho-corasick/blob/3852632f10587db0ff72ef29e88d58bf305a0946/src/packed/rabinkarp.rs
*/
use crate::ext::Pointer;
/// A forward substring searcher using the Rabin-Karp algorithm.
///
/// Note that, as a lower level API, a `Finder` does not have access to the
/// needle it was constructed with. For this reason, executing a search
/// with a `Finder` requires passing both the needle and the haystack,
/// where the needle is exactly equivalent to the one given to the `Finder`
/// at construction time. This design was chosen so that callers can have
/// more precise control over where and how many times a needle is stored.
/// For example, in cases where Rabin-Karp is just one of several possible
/// substring search algorithms.
#[derive(Clone, Debug)]
pub struct Finder {
/// The actual hash.
hash: Hash,
/// The factor needed to multiply a byte by in order to subtract it from
/// the hash. It is defined to be 2^(n-1) (using wrapping exponentiation),
/// where n is the length of the needle. This is how we "remove" a byte
/// from the hash once the hash window rolls past it.
hash_2pow: u32,
}
impl Finder {
/// Create a new Rabin-Karp forward searcher for the given `needle`.
///
/// The needle may be empty. The empty needle matches at every byte offset.
///
/// Note that callers must pass the same needle to all search calls using
/// this `Finder`.
#[inline]
pub fn new(needle: &[u8]) -> Finder {
let mut s = Finder { hash: Hash::new(), hash_2pow: 1 };
let first_byte = match needle.get(0) {
None => return s,
Some(&first_byte) => first_byte,
};
s.hash.add(first_byte);
for b in needle.iter().copied().skip(1) {
s.hash.add(b);
s.hash_2pow = s.hash_2pow.wrapping_shl(1);
}
s
}
/// Return the first occurrence of the `needle` in the `haystack`
/// given. If no such occurrence exists, then `None` is returned.
///
/// The `needle` provided must match the needle given to this finder at
/// construction time.
///
/// The maximum value this can return is `haystack.len()`, which can only
/// occur when the needle and haystack both have length zero. Otherwise,
/// for non-empty haystacks, the maximum value is `haystack.len() - 1`.
#[inline]
pub fn find(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
unsafe {
let hstart = haystack.as_ptr();
let hend = hstart.add(haystack.len());
let nstart = needle.as_ptr();
let nend = nstart.add(needle.len());
let found = self.find_raw(hstart, hend, nstart, nend)?;
Some(found.distance(hstart))
}
}
/// Like `find`, but accepts and returns raw pointers.
///
/// When a match is found, the pointer returned is guaranteed to be
/// `>= start` and `<= end`. The pointer returned is only ever equivalent
/// to `end` when both the needle and haystack are empty. (That is, the
/// empty string matches the empty string.)
///
/// This routine is useful if you're already using raw pointers and would
/// like to avoid converting back to a slice before executing a search.
///
/// # Safety
///
/// Note that `start` and `end` below refer to both pairs of pointers given
/// to this routine. That is, the conditions apply to both `hstart`/`hend`
/// and `nstart`/`nend`.
///
/// * Both `start` and `end` must be valid for reads.
/// * Both `start` and `end` must point to an initialized value.
/// * Both `start` and `end` must point to the same allocated object and
/// must either be in bounds or at most one byte past the end of the
/// allocated object.
/// * Both `start` and `end` must be _derived from_ a pointer to the same
/// object.
/// * The distance between `start` and `end` must not overflow `isize`.
/// * The distance being in bounds must not rely on "wrapping around" the
/// address space.
/// * It must be the case that `start <= end`.
#[inline]
pub unsafe fn find_raw(
&self,
hstart: *const u8,
hend: *const u8,
nstart: *const u8,
nend: *const u8,
) -> Option<*const u8> {
let hlen = hend.distance(hstart);
let nlen = nend.distance(nstart);
if nlen > hlen {
return None;
}
let mut cur = hstart;
let end = hend.sub(nlen);
let mut hash = Hash::forward(cur, cur.add(nlen));
loop {
if self.hash == hash && is_equal_raw(cur, nstart, nlen) {
return Some(cur);
}
if cur >= end {
return None;
}
hash.roll(self, cur.read(), cur.add(nlen).read());
cur = cur.add(1);
}
}
}
/// A reverse substring searcher using the Rabin-Karp algorithm.
#[derive(Clone, Debug)]
pub struct FinderRev(Finder);
impl FinderRev {
/// Create a new Rabin-Karp reverse searcher for the given `needle`.
#[inline]
pub fn new(needle: &[u8]) -> FinderRev {
let mut s = FinderRev(Finder { hash: Hash::new(), hash_2pow: 1 });
let last_byte = match needle.last() {
None => return s,
Some(&last_byte) => last_byte,
};
s.0.hash.add(last_byte);
for b in needle.iter().rev().copied().skip(1) {
s.0.hash.add(b);
s.0.hash_2pow = s.0.hash_2pow.wrapping_shl(1);
}
s
}
/// Return the last occurrence of the `needle` in the `haystack`
/// given. If no such occurrence exists, then `None` is returned.
///
/// The `needle` provided must match the needle given to this finder at
/// construction time.
///
/// The maximum value this can return is `haystack.len()`, which can only
/// occur when the needle and haystack both have length zero. Otherwise,
/// for non-empty haystacks, the maximum value is `haystack.len() - 1`.
#[inline]
pub fn rfind(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
unsafe {
let hstart = haystack.as_ptr();
let hend = hstart.add(haystack.len());
let nstart = needle.as_ptr();
let nend = nstart.add(needle.len());
let found = self.rfind_raw(hstart, hend, nstart, nend)?;
Some(found.distance(hstart))
}
}
/// Like `rfind`, but accepts and returns raw pointers.
///
/// When a match is found, the pointer returned is guaranteed to be
/// `>= start` and `<= end`. The pointer returned is only ever equivalent
/// to `end` when both the needle and haystack are empty. (That is, the
/// empty string matches the empty string.)
///
/// This routine is useful if you're already using raw pointers and would
/// like to avoid converting back to a slice before executing a search.
///
/// # Safety
///
/// Note that `start` and `end` below refer to both pairs of pointers given
/// to this routine. That is, the conditions apply to both `hstart`/`hend`
/// and `nstart`/`nend`.
///
/// * Both `start` and `end` must be valid for reads.
/// * Both `start` and `end` must point to an initialized value.
/// * Both `start` and `end` must point to the same allocated object and
/// must either be in bounds or at most one byte past the end of the
/// allocated object.
/// * Both `start` and `end` must be _derived from_ a pointer to the same
/// object.
/// * The distance between `start` and `end` must not overflow `isize`.
/// * The distance being in bounds must not rely on "wrapping around" the
/// address space.
/// * It must be the case that `start <= end`.
#[inline]
pub unsafe fn rfind_raw(
&self,
hstart: *const u8,
hend: *const u8,
nstart: *const u8,
nend: *const u8,
) -> Option<*const u8> {
let hlen = hend.distance(hstart);
let nlen = nend.distance(nstart);
if nlen > hlen {
return None;
}
let mut cur = hend.sub(nlen);
let start = hstart;
let mut hash = Hash::reverse(cur, cur.add(nlen));
loop {
if self.0.hash == hash && is_equal_raw(cur, nstart, nlen) {
return Some(cur);
}
if cur <= start {
return None;
}
cur = cur.sub(1);
hash.roll(&self.0, cur.add(nlen).read(), cur.read());
}
}
}
/// Whether RK is believed to be very fast for the given needle/haystack.
#[inline]
pub(crate) fn is_fast(haystack: &[u8], _needle: &[u8]) -> bool {
haystack.len() < 16
}
/// A Rabin-Karp hash. This might represent the hash of a needle, or the hash
/// of a rolling window in the haystack.
#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
struct Hash(u32);
impl Hash {
/// Create a new hash that represents the empty string.
#[inline(always)]
fn new() -> Hash {
Hash(0)
}
/// Create a new hash from the bytes given for use in forward searches.
///
/// # Safety
///
/// The given pointers must be valid to read from within their range.
#[inline(always)]
unsafe fn forward(mut start: *const u8, end: *const u8) -> Hash {
let mut hash = Hash::new();
while start < end {
hash.add(start.read());
start = start.add(1);
}
hash
}
/// Create a new hash from the bytes given for use in reverse searches.
///
/// # Safety
///
/// The given pointers must be valid to read from within their range.
#[inline(always)]
unsafe fn reverse(start: *const u8, mut end: *const u8) -> Hash {
let mut hash = Hash::new();
while start < end {
end = end.sub(1);
hash.add(end.read());
}
hash
}
/// Add 'new' and remove 'old' from this hash. The given needle hash should
/// correspond to the hash computed for the needle being searched for.
///
/// This is meant to be used when the rolling window of the haystack is
/// advanced.
#[inline(always)]
fn roll(&mut self, finder: &Finder, old: u8, new: u8) {
self.del(finder, old);
self.add(new);
}
/// Add a byte to this hash.
#[inline(always)]
fn add(&mut self, byte: u8) {
self.0 = self.0.wrapping_shl(1).wrapping_add(u32::from(byte));
}
/// Remove a byte from this hash. The given needle hash should correspond
/// to the hash computed for the needle being searched for.
#[inline(always)]
fn del(&mut self, finder: &Finder, byte: u8) {
let factor = finder.hash_2pow;
self.0 = self.0.wrapping_sub(u32::from(byte).wrapping_mul(factor));
}
}
/// Returns true when `x[i] == y[i]` for all `0 <= i < n`.
///
/// We forcefully don't inline this to hint at the compiler that it is unlikely
/// to be called. This causes the inner rabinkarp loop above to be a bit
/// tighter and leads to some performance improvement. See the
/// memmem/krate/prebuilt/sliceslice-words/words benchmark.
///
/// # Safety
///
/// Same as `crate::arch::all::is_equal_raw`.
#[cold]
#[inline(never)]
unsafe fn is_equal_raw(x: *const u8, y: *const u8, n: usize) -> bool {
crate::arch::all::is_equal_raw(x, y, n)
}
#[cfg(test)]
mod tests {
use super::*;
define_substring_forward_quickcheck!(|h, n| Some(
Finder::new(n).find(h, n)
));
define_substring_reverse_quickcheck!(|h, n| Some(
FinderRev::new(n).rfind(h, n)
));
#[test]
fn forward() {
crate::tests::substring::Runner::new()
.fwd(|h, n| Some(Finder::new(n).find(h, n)))
.run();
}
#[test]
fn reverse() {
crate::tests::substring::Runner::new()
.rev(|h, n| Some(FinderRev::new(n).rfind(h, n)))
.run();
}
}

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/*!
An implementation of the [Shift-Or substring search algorithm][shiftor].
[shiftor]: https://en.wikipedia.org/wiki/Bitap_algorithm
*/
use alloc::boxed::Box;
/// The type of our mask.
///
/// While we don't expose anyway to configure this in the public API, if one
/// really needs less memory usage or support for longer needles, then it is
/// suggested to copy the code from this module and modify it to fit your
/// needs. The code below is written to be correct regardless of whether Mask
/// is a u8, u16, u32, u64 or u128.
type Mask = u16;
/// A forward substring searcher using the Shift-Or algorithm.
#[derive(Debug)]
pub struct Finder {
masks: Box<[Mask; 256]>,
needle_len: usize,
}
impl Finder {
const MAX_NEEDLE_LEN: usize = (Mask::BITS - 1) as usize;
/// Create a new Shift-Or forward searcher for the given `needle`.
///
/// The needle may be empty. The empty needle matches at every byte offset.
#[inline]
pub fn new(needle: &[u8]) -> Option<Finder> {
let needle_len = needle.len();
if needle_len > Finder::MAX_NEEDLE_LEN {
// A match is found when bit 7 is set in 'result' in the search
// routine below. So our needle can't be bigger than 7. We could
// permit bigger needles by using u16, u32 or u64 for our mask
// entries. But this is all we need for this example.
return None;
}
let mut searcher = Finder { masks: Box::from([!0; 256]), needle_len };
for (i, &byte) in needle.iter().enumerate() {
searcher.masks[usize::from(byte)] &= !(1 << i);
}
Some(searcher)
}
/// Return the first occurrence of the needle given to `Finder::new` in
/// the `haystack` given. If no such occurrence exists, then `None` is
/// returned.
///
/// Unlike most other substring search implementations in this crate, this
/// finder does not require passing the needle at search time. A match can
/// be determined without the needle at all since the required information
/// is already encoded into this finder at construction time.
///
/// The maximum value this can return is `haystack.len()`, which can only
/// occur when the needle and haystack both have length zero. Otherwise,
/// for non-empty haystacks, the maximum value is `haystack.len() - 1`.
#[inline]
pub fn find(&self, haystack: &[u8]) -> Option<usize> {
if self.needle_len == 0 {
return Some(0);
}
let mut result = !1;
for (i, &byte) in haystack.iter().enumerate() {
result |= self.masks[usize::from(byte)];
result <<= 1;
if result & (1 << self.needle_len) == 0 {
return Some(i + 1 - self.needle_len);
}
}
None
}
}
#[cfg(test)]
mod tests {
use super::*;
define_substring_forward_quickcheck!(|h, n| Some(Finder::new(n)?.find(h)));
#[test]
fn forward() {
crate::tests::substring::Runner::new()
.fwd(|h, n| Some(Finder::new(n)?.find(h)))
.run();
}
}

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/*!
An implementation of the [Two-Way substring search algorithm][two-way].
[`Finder`] can be built for forward searches, while [`FinderRev`] can be built
for reverse searches.
Two-Way makes for a nice general purpose substring search algorithm because of
its time and space complexity properties. It also performs well in practice.
Namely, with `m = len(needle)` and `n = len(haystack)`, Two-Way takes `O(m)`
time to create a finder, `O(1)` space and `O(n)` search time. In other words,
the preprocessing step is quick, doesn't require any heap memory and the worst
case search time is guaranteed to be linear in the haystack regardless of the
size of the needle.
While vector algorithms will usually beat Two-Way handedly, vector algorithms
also usually have pathological or edge cases that are better handled by Two-Way.
Moreover, not all targets support vector algorithms or implementations for them
simply may not exist yet.
Two-Way can be found in the `memmem` implementations in at least [GNU libc] and
[musl].
[two-way]: https://en.wikipedia.org/wiki/Two-way_string-matching_algorithm
[GNU libc]: https://www.gnu.org/software/libc/
[musl]: https://www.musl-libc.org/
*/
use core::cmp;
use crate::{
arch::all::{is_prefix, is_suffix},
memmem::Pre,
};
/// A forward substring searcher that uses the Two-Way algorithm.
#[derive(Clone, Copy, Debug)]
pub struct Finder(TwoWay);
/// A reverse substring searcher that uses the Two-Way algorithm.
#[derive(Clone, Copy, Debug)]
pub struct FinderRev(TwoWay);
/// An implementation of the TwoWay substring search algorithm.
///
/// This searcher supports forward and reverse search, although not
/// simultaneously. It runs in `O(n + m)` time and `O(1)` space, where
/// `n ~ len(needle)` and `m ~ len(haystack)`.
///
/// The implementation here roughly matches that which was developed by
/// Crochemore and Perrin in their 1991 paper "Two-way string-matching." The
/// changes in this implementation are 1) the use of zero-based indices, 2) a
/// heuristic skip table based on the last byte (borrowed from Rust's standard
/// library) and 3) the addition of heuristics for a fast skip loop. For (3),
/// callers can pass any kind of prefilter they want, but usually it's one
/// based on a heuristic that uses an approximate background frequency of bytes
/// to choose rare bytes to quickly look for candidate match positions. Note
/// though that currently, this prefilter functionality is not exposed directly
/// in the public API. (File an issue if you want it and provide a use case
/// please.)
///
/// The heuristic for fast skipping is automatically shut off if it's
/// detected to be ineffective at search time. Generally, this only occurs in
/// pathological cases. But this is generally necessary in order to preserve
/// a `O(n + m)` time bound.
///
/// The code below is fairly complex and not obviously correct at all. It's
/// likely necessary to read the Two-Way paper cited above in order to fully
/// grok this code. The essence of it is:
///
/// 1. Do something to detect a "critical" position in the needle.
/// 2. For the current position in the haystack, look if `needle[critical..]`
/// matches at that position.
/// 3. If so, look if `needle[..critical]` matches.
/// 4. If a mismatch occurs, shift the search by some amount based on the
/// critical position and a pre-computed shift.
///
/// This type is wrapped in the forward and reverse finders that expose
/// consistent forward or reverse APIs.
#[derive(Clone, Copy, Debug)]
struct TwoWay {
/// A small bitset used as a quick prefilter (in addition to any prefilter
/// given by the caller). Namely, a bit `i` is set if and only if `b%64==i`
/// for any `b == needle[i]`.
///
/// When used as a prefilter, if the last byte at the current candidate
/// position is NOT in this set, then we can skip that entire candidate
/// position (the length of the needle). This is essentially the shift
/// trick found in Boyer-Moore, but only applied to bytes that don't appear
/// in the needle.
///
/// N.B. This trick was inspired by something similar in std's
/// implementation of Two-Way.
byteset: ApproximateByteSet,
/// A critical position in needle. Specifically, this position corresponds
/// to beginning of either the minimal or maximal suffix in needle. (N.B.
/// See SuffixType below for why "minimal" isn't quite the correct word
/// here.)
///
/// This is the position at which every search begins. Namely, search
/// starts by scanning text to the right of this position, and only if
/// there's a match does the text to the left of this position get scanned.
critical_pos: usize,
/// The amount we shift by in the Two-Way search algorithm. This
/// corresponds to the "small period" and "large period" cases.
shift: Shift,
}
impl Finder {
/// Create a searcher that finds occurrences of the given `needle`.
///
/// An empty `needle` results in a match at every position in a haystack,
/// including at `haystack.len()`.
#[inline]
pub fn new(needle: &[u8]) -> Finder {
let byteset = ApproximateByteSet::new(needle);
let min_suffix = Suffix::forward(needle, SuffixKind::Minimal);
let max_suffix = Suffix::forward(needle, SuffixKind::Maximal);
let (period_lower_bound, critical_pos) =
if min_suffix.pos > max_suffix.pos {
(min_suffix.period, min_suffix.pos)
} else {
(max_suffix.period, max_suffix.pos)
};
let shift = Shift::forward(needle, period_lower_bound, critical_pos);
Finder(TwoWay { byteset, critical_pos, shift })
}
/// Returns the first occurrence of `needle` in the given `haystack`, or
/// `None` if no such occurrence could be found.
///
/// The `needle` given must be the same as the `needle` provided to
/// [`Finder::new`].
///
/// An empty `needle` results in a match at every position in a haystack,
/// including at `haystack.len()`.
#[inline]
pub fn find(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
self.find_with_prefilter(None, haystack, needle)
}
/// This is like [`Finder::find`], but it accepts a prefilter for
/// accelerating searches.
///
/// Currently this is not exposed in the public API because, at the time
/// of writing, I didn't want to spend time thinking about how to expose
/// the prefilter infrastructure (if at all). If you have a compelling use
/// case for exposing this routine, please create an issue. Do *not* open
/// a PR that just exposes `Pre` and friends. Exporting this routine will
/// require API design.
#[inline(always)]
pub(crate) fn find_with_prefilter(
&self,
pre: Option<Pre<'_>>,
haystack: &[u8],
needle: &[u8],
) -> Option<usize> {
match self.0.shift {
Shift::Small { period } => {
self.find_small_imp(pre, haystack, needle, period)
}
Shift::Large { shift } => {
self.find_large_imp(pre, haystack, needle, shift)
}
}
}
// Each of the two search implementations below can be accelerated by a
// prefilter, but it is not always enabled. To avoid its overhead when
// its disabled, we explicitly inline each search implementation based on
// whether a prefilter will be used or not. The decision on which to use
// is made in the parent meta searcher.
#[inline(always)]
fn find_small_imp(
&self,
mut pre: Option<Pre<'_>>,
haystack: &[u8],
needle: &[u8],
period: usize,
) -> Option<usize> {
let mut pos = 0;
let mut shift = 0;
let last_byte_pos = match needle.len().checked_sub(1) {
None => return Some(pos),
Some(last_byte) => last_byte,
};
while pos + needle.len() <= haystack.len() {
let mut i = cmp::max(self.0.critical_pos, shift);
if let Some(pre) = pre.as_mut() {
if pre.is_effective() {
pos += pre.find(&haystack[pos..])?;
shift = 0;
i = self.0.critical_pos;
if pos + needle.len() > haystack.len() {
return None;
}
}
}
if !self.0.byteset.contains(haystack[pos + last_byte_pos]) {
pos += needle.len();
shift = 0;
continue;
}
while i < needle.len() && needle[i] == haystack[pos + i] {
i += 1;
}
if i < needle.len() {
pos += i - self.0.critical_pos + 1;
shift = 0;
} else {
let mut j = self.0.critical_pos;
while j > shift && needle[j] == haystack[pos + j] {
j -= 1;
}
if j <= shift && needle[shift] == haystack[pos + shift] {
return Some(pos);
}
pos += period;
shift = needle.len() - period;
}
}
None
}
#[inline(always)]
fn find_large_imp(
&self,
mut pre: Option<Pre<'_>>,
haystack: &[u8],
needle: &[u8],
shift: usize,
) -> Option<usize> {
let mut pos = 0;
let last_byte_pos = match needle.len().checked_sub(1) {
None => return Some(pos),
Some(last_byte) => last_byte,
};
'outer: while pos + needle.len() <= haystack.len() {
if let Some(pre) = pre.as_mut() {
if pre.is_effective() {
pos += pre.find(&haystack[pos..])?;
if pos + needle.len() > haystack.len() {
return None;
}
}
}
if !self.0.byteset.contains(haystack[pos + last_byte_pos]) {
pos += needle.len();
continue;
}
let mut i = self.0.critical_pos;
while i < needle.len() && needle[i] == haystack[pos + i] {
i += 1;
}
if i < needle.len() {
pos += i - self.0.critical_pos + 1;
} else {
for j in (0..self.0.critical_pos).rev() {
if needle[j] != haystack[pos + j] {
pos += shift;
continue 'outer;
}
}
return Some(pos);
}
}
None
}
}
impl FinderRev {
/// Create a searcher that finds occurrences of the given `needle`.
///
/// An empty `needle` results in a match at every position in a haystack,
/// including at `haystack.len()`.
#[inline]
pub fn new(needle: &[u8]) -> FinderRev {
let byteset = ApproximateByteSet::new(needle);
let min_suffix = Suffix::reverse(needle, SuffixKind::Minimal);
let max_suffix = Suffix::reverse(needle, SuffixKind::Maximal);
let (period_lower_bound, critical_pos) =
if min_suffix.pos < max_suffix.pos {
(min_suffix.period, min_suffix.pos)
} else {
(max_suffix.period, max_suffix.pos)
};
let shift = Shift::reverse(needle, period_lower_bound, critical_pos);
FinderRev(TwoWay { byteset, critical_pos, shift })
}
/// Returns the last occurrence of `needle` in the given `haystack`, or
/// `None` if no such occurrence could be found.
///
/// The `needle` given must be the same as the `needle` provided to
/// [`FinderRev::new`].
///
/// An empty `needle` results in a match at every position in a haystack,
/// including at `haystack.len()`.
#[inline]
pub fn rfind(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
// For the reverse case, we don't use a prefilter. It's plausible that
// perhaps we should, but it's a lot of additional code to do it, and
// it's not clear that it's actually worth it. If you have a really
// compelling use case for this, please file an issue.
match self.0.shift {
Shift::Small { period } => {
self.rfind_small_imp(haystack, needle, period)
}
Shift::Large { shift } => {
self.rfind_large_imp(haystack, needle, shift)
}
}
}
#[inline(always)]
fn rfind_small_imp(
&self,
haystack: &[u8],
needle: &[u8],
period: usize,
) -> Option<usize> {
let nlen = needle.len();
let mut pos = haystack.len();
let mut shift = nlen;
let first_byte = match needle.get(0) {
None => return Some(pos),
Some(&first_byte) => first_byte,
};
while pos >= nlen {
if !self.0.byteset.contains(haystack[pos - nlen]) {
pos -= nlen;
shift = nlen;
continue;
}
let mut i = cmp::min(self.0.critical_pos, shift);
while i > 0 && needle[i - 1] == haystack[pos - nlen + i - 1] {
i -= 1;
}
if i > 0 || first_byte != haystack[pos - nlen] {
pos -= self.0.critical_pos - i + 1;
shift = nlen;
} else {
let mut j = self.0.critical_pos;
while j < shift && needle[j] == haystack[pos - nlen + j] {
j += 1;
}
if j >= shift {
return Some(pos - nlen);
}
pos -= period;
shift = period;
}
}
None
}
#[inline(always)]
fn rfind_large_imp(
&self,
haystack: &[u8],
needle: &[u8],
shift: usize,
) -> Option<usize> {
let nlen = needle.len();
let mut pos = haystack.len();
let first_byte = match needle.get(0) {
None => return Some(pos),
Some(&first_byte) => first_byte,
};
while pos >= nlen {
if !self.0.byteset.contains(haystack[pos - nlen]) {
pos -= nlen;
continue;
}
let mut i = self.0.critical_pos;
while i > 0 && needle[i - 1] == haystack[pos - nlen + i - 1] {
i -= 1;
}
if i > 0 || first_byte != haystack[pos - nlen] {
pos -= self.0.critical_pos - i + 1;
} else {
let mut j = self.0.critical_pos;
while j < nlen && needle[j] == haystack[pos - nlen + j] {
j += 1;
}
if j == nlen {
return Some(pos - nlen);
}
pos -= shift;
}
}
None
}
}
/// A representation of the amount we're allowed to shift by during Two-Way
/// search.
///
/// When computing a critical factorization of the needle, we find the position
/// of the critical factorization by finding the needle's maximal (or minimal)
/// suffix, along with the period of that suffix. It turns out that the period
/// of that suffix is a lower bound on the period of the needle itself.
///
/// This lower bound is equivalent to the actual period of the needle in
/// some cases. To describe that case, we denote the needle as `x` where
/// `x = uv` and `v` is the lexicographic maximal suffix of `v`. The lower
/// bound given here is always the period of `v`, which is `<= period(x)`. The
/// case where `period(v) == period(x)` occurs when `len(u) < (len(x) / 2)` and
/// where `u` is a suffix of `v[0..period(v)]`.
///
/// This case is important because the search algorithm for when the
/// periods are equivalent is slightly different than the search algorithm
/// for when the periods are not equivalent. In particular, when they aren't
/// equivalent, we know that the period of the needle is no less than half its
/// length. In this case, we shift by an amount less than or equal to the
/// period of the needle (determined by the maximum length of the components
/// of the critical factorization of `x`, i.e., `max(len(u), len(v))`)..
///
/// The above two cases are represented by the variants below. Each entails
/// a different instantiation of the Two-Way search algorithm.
///
/// N.B. If we could find a way to compute the exact period in all cases,
/// then we could collapse this case analysis and simplify the algorithm. The
/// Two-Way paper suggests this is possible, but more reading is required to
/// grok why the authors didn't pursue that path.
#[derive(Clone, Copy, Debug)]
enum Shift {
Small { period: usize },
Large { shift: usize },
}
impl Shift {
/// Compute the shift for a given needle in the forward direction.
///
/// This requires a lower bound on the period and a critical position.
/// These can be computed by extracting both the minimal and maximal
/// lexicographic suffixes, and choosing the right-most starting position.
/// The lower bound on the period is then the period of the chosen suffix.
fn forward(
needle: &[u8],
period_lower_bound: usize,
critical_pos: usize,
) -> Shift {
let large = cmp::max(critical_pos, needle.len() - critical_pos);
if critical_pos * 2 >= needle.len() {
return Shift::Large { shift: large };
}
let (u, v) = needle.split_at(critical_pos);
if !is_suffix(&v[..period_lower_bound], u) {
return Shift::Large { shift: large };
}
Shift::Small { period: period_lower_bound }
}
/// Compute the shift for a given needle in the reverse direction.
///
/// This requires a lower bound on the period and a critical position.
/// These can be computed by extracting both the minimal and maximal
/// lexicographic suffixes, and choosing the left-most starting position.
/// The lower bound on the period is then the period of the chosen suffix.
fn reverse(
needle: &[u8],
period_lower_bound: usize,
critical_pos: usize,
) -> Shift {
let large = cmp::max(critical_pos, needle.len() - critical_pos);
if (needle.len() - critical_pos) * 2 >= needle.len() {
return Shift::Large { shift: large };
}
let (v, u) = needle.split_at(critical_pos);
if !is_prefix(&v[v.len() - period_lower_bound..], u) {
return Shift::Large { shift: large };
}
Shift::Small { period: period_lower_bound }
}
}
/// A suffix extracted from a needle along with its period.
#[derive(Debug)]
struct Suffix {
/// The starting position of this suffix.
///
/// If this is a forward suffix, then `&bytes[pos..]` can be used. If this
/// is a reverse suffix, then `&bytes[..pos]` can be used. That is, for
/// forward suffixes, this is an inclusive starting position, where as for
/// reverse suffixes, this is an exclusive ending position.
pos: usize,
/// The period of this suffix.
///
/// Note that this is NOT necessarily the period of the string from which
/// this suffix comes from. (It is always less than or equal to the period
/// of the original string.)
period: usize,
}
impl Suffix {
fn forward(needle: &[u8], kind: SuffixKind) -> Suffix {
// suffix represents our maximal (or minimal) suffix, along with
// its period.
let mut suffix = Suffix { pos: 0, period: 1 };
// The start of a suffix in `needle` that we are considering as a
// more maximal (or minimal) suffix than what's in `suffix`.
let mut candidate_start = 1;
// The current offset of our suffixes that we're comparing.
//
// When the characters at this offset are the same, then we mush on
// to the next position since no decision is possible. When the
// candidate's character is greater (or lesser) than the corresponding
// character than our current maximal (or minimal) suffix, then the
// current suffix is changed over to the candidate and we restart our
// search. Otherwise, the candidate suffix is no good and we restart
// our search on the next candidate.
//
// The three cases above correspond to the three cases in the loop
// below.
let mut offset = 0;
while candidate_start + offset < needle.len() {
let current = needle[suffix.pos + offset];
let candidate = needle[candidate_start + offset];
match kind.cmp(current, candidate) {
SuffixOrdering::Accept => {
suffix = Suffix { pos: candidate_start, period: 1 };
candidate_start += 1;
offset = 0;
}
SuffixOrdering::Skip => {
candidate_start += offset + 1;
offset = 0;
suffix.period = candidate_start - suffix.pos;
}
SuffixOrdering::Push => {
if offset + 1 == suffix.period {
candidate_start += suffix.period;
offset = 0;
} else {
offset += 1;
}
}
}
}
suffix
}
fn reverse(needle: &[u8], kind: SuffixKind) -> Suffix {
// See the comments in `forward` for how this works.
let mut suffix = Suffix { pos: needle.len(), period: 1 };
if needle.len() == 1 {
return suffix;
}
let mut candidate_start = match needle.len().checked_sub(1) {
None => return suffix,
Some(candidate_start) => candidate_start,
};
let mut offset = 0;
while offset < candidate_start {
let current = needle[suffix.pos - offset - 1];
let candidate = needle[candidate_start - offset - 1];
match kind.cmp(current, candidate) {
SuffixOrdering::Accept => {
suffix = Suffix { pos: candidate_start, period: 1 };
candidate_start -= 1;
offset = 0;
}
SuffixOrdering::Skip => {
candidate_start -= offset + 1;
offset = 0;
suffix.period = suffix.pos - candidate_start;
}
SuffixOrdering::Push => {
if offset + 1 == suffix.period {
candidate_start -= suffix.period;
offset = 0;
} else {
offset += 1;
}
}
}
}
suffix
}
}
/// The kind of suffix to extract.
#[derive(Clone, Copy, Debug)]
enum SuffixKind {
/// Extract the smallest lexicographic suffix from a string.
///
/// Technically, this doesn't actually pick the smallest lexicographic
/// suffix. e.g., Given the choice between `a` and `aa`, this will choose
/// the latter over the former, even though `a < aa`. The reasoning for
/// this isn't clear from the paper, but it still smells like a minimal
/// suffix.
Minimal,
/// Extract the largest lexicographic suffix from a string.
///
/// Unlike `Minimal`, this really does pick the maximum suffix. e.g., Given
/// the choice between `z` and `zz`, this will choose the latter over the
/// former.
Maximal,
}
/// The result of comparing corresponding bytes between two suffixes.
#[derive(Clone, Copy, Debug)]
enum SuffixOrdering {
/// This occurs when the given candidate byte indicates that the candidate
/// suffix is better than the current maximal (or minimal) suffix. That is,
/// the current candidate suffix should supplant the current maximal (or
/// minimal) suffix.
Accept,
/// This occurs when the given candidate byte excludes the candidate suffix
/// from being better than the current maximal (or minimal) suffix. That
/// is, the current candidate suffix should be dropped and the next one
/// should be considered.
Skip,
/// This occurs when no decision to accept or skip the candidate suffix
/// can be made, e.g., when corresponding bytes are equivalent. In this
/// case, the next corresponding bytes should be compared.
Push,
}
impl SuffixKind {
/// Returns true if and only if the given candidate byte indicates that
/// it should replace the current suffix as the maximal (or minimal)
/// suffix.
fn cmp(self, current: u8, candidate: u8) -> SuffixOrdering {
use self::SuffixOrdering::*;
match self {
SuffixKind::Minimal if candidate < current => Accept,
SuffixKind::Minimal if candidate > current => Skip,
SuffixKind::Minimal => Push,
SuffixKind::Maximal if candidate > current => Accept,
SuffixKind::Maximal if candidate < current => Skip,
SuffixKind::Maximal => Push,
}
}
}
/// A bitset used to track whether a particular byte exists in a needle or not.
///
/// Namely, bit 'i' is set if and only if byte%64==i for any byte in the
/// needle. If a particular byte in the haystack is NOT in this set, then one
/// can conclude that it is also not in the needle, and thus, one can advance
/// in the haystack by needle.len() bytes.
#[derive(Clone, Copy, Debug)]
struct ApproximateByteSet(u64);
impl ApproximateByteSet {
/// Create a new set from the given needle.
fn new(needle: &[u8]) -> ApproximateByteSet {
let mut bits = 0;
for &b in needle {
bits |= 1 << (b % 64);
}
ApproximateByteSet(bits)
}
/// Return true if and only if the given byte might be in this set. This
/// may return a false positive, but will never return a false negative.
#[inline(always)]
fn contains(&self, byte: u8) -> bool {
self.0 & (1 << (byte % 64)) != 0
}
}
#[cfg(test)]
mod tests {
use alloc::vec::Vec;
use super::*;
/// Convenience wrapper for computing the suffix as a byte string.
fn get_suffix_forward(needle: &[u8], kind: SuffixKind) -> (&[u8], usize) {
let s = Suffix::forward(needle, kind);
(&needle[s.pos..], s.period)
}
/// Convenience wrapper for computing the reverse suffix as a byte string.
fn get_suffix_reverse(needle: &[u8], kind: SuffixKind) -> (&[u8], usize) {
let s = Suffix::reverse(needle, kind);
(&needle[..s.pos], s.period)
}
/// Return all of the non-empty suffixes in the given byte string.
fn suffixes(bytes: &[u8]) -> Vec<&[u8]> {
(0..bytes.len()).map(|i| &bytes[i..]).collect()
}
/// Return the lexicographically maximal suffix of the given byte string.
fn naive_maximal_suffix_forward(needle: &[u8]) -> &[u8] {
let mut sufs = suffixes(needle);
sufs.sort();
sufs.pop().unwrap()
}
/// Return the lexicographically maximal suffix of the reverse of the given
/// byte string.
fn naive_maximal_suffix_reverse(needle: &[u8]) -> Vec<u8> {
let mut reversed = needle.to_vec();
reversed.reverse();
let mut got = naive_maximal_suffix_forward(&reversed).to_vec();
got.reverse();
got
}
define_substring_forward_quickcheck!(|h, n| Some(
Finder::new(n).find(h, n)
));
define_substring_reverse_quickcheck!(|h, n| Some(
FinderRev::new(n).rfind(h, n)
));
#[test]
fn forward() {
crate::tests::substring::Runner::new()
.fwd(|h, n| Some(Finder::new(n).find(h, n)))
.run();
}
#[test]
fn reverse() {
crate::tests::substring::Runner::new()
.rev(|h, n| Some(FinderRev::new(n).rfind(h, n)))
.run();
}
#[test]
fn suffix_forward() {
macro_rules! assert_suffix_min {
($given:expr, $expected:expr, $period:expr) => {
let (got_suffix, got_period) =
get_suffix_forward($given.as_bytes(), SuffixKind::Minimal);
let got_suffix = core::str::from_utf8(got_suffix).unwrap();
assert_eq!(($expected, $period), (got_suffix, got_period));
};
}
macro_rules! assert_suffix_max {
($given:expr, $expected:expr, $period:expr) => {
let (got_suffix, got_period) =
get_suffix_forward($given.as_bytes(), SuffixKind::Maximal);
let got_suffix = core::str::from_utf8(got_suffix).unwrap();
assert_eq!(($expected, $period), (got_suffix, got_period));
};
}
assert_suffix_min!("a", "a", 1);
assert_suffix_max!("a", "a", 1);
assert_suffix_min!("ab", "ab", 2);
assert_suffix_max!("ab", "b", 1);
assert_suffix_min!("ba", "a", 1);
assert_suffix_max!("ba", "ba", 2);
assert_suffix_min!("abc", "abc", 3);
assert_suffix_max!("abc", "c", 1);
assert_suffix_min!("acb", "acb", 3);
assert_suffix_max!("acb", "cb", 2);
assert_suffix_min!("cba", "a", 1);
assert_suffix_max!("cba", "cba", 3);
assert_suffix_min!("abcabc", "abcabc", 3);
assert_suffix_max!("abcabc", "cabc", 3);
assert_suffix_min!("abcabcabc", "abcabcabc", 3);
assert_suffix_max!("abcabcabc", "cabcabc", 3);
assert_suffix_min!("abczz", "abczz", 5);
assert_suffix_max!("abczz", "zz", 1);
assert_suffix_min!("zzabc", "abc", 3);
assert_suffix_max!("zzabc", "zzabc", 5);
assert_suffix_min!("aaa", "aaa", 1);
assert_suffix_max!("aaa", "aaa", 1);
assert_suffix_min!("foobar", "ar", 2);
assert_suffix_max!("foobar", "r", 1);
}
#[test]
fn suffix_reverse() {
macro_rules! assert_suffix_min {
($given:expr, $expected:expr, $period:expr) => {
let (got_suffix, got_period) =
get_suffix_reverse($given.as_bytes(), SuffixKind::Minimal);
let got_suffix = core::str::from_utf8(got_suffix).unwrap();
assert_eq!(($expected, $period), (got_suffix, got_period));
};
}
macro_rules! assert_suffix_max {
($given:expr, $expected:expr, $period:expr) => {
let (got_suffix, got_period) =
get_suffix_reverse($given.as_bytes(), SuffixKind::Maximal);
let got_suffix = core::str::from_utf8(got_suffix).unwrap();
assert_eq!(($expected, $period), (got_suffix, got_period));
};
}
assert_suffix_min!("a", "a", 1);
assert_suffix_max!("a", "a", 1);
assert_suffix_min!("ab", "a", 1);
assert_suffix_max!("ab", "ab", 2);
assert_suffix_min!("ba", "ba", 2);
assert_suffix_max!("ba", "b", 1);
assert_suffix_min!("abc", "a", 1);
assert_suffix_max!("abc", "abc", 3);
assert_suffix_min!("acb", "a", 1);
assert_suffix_max!("acb", "ac", 2);
assert_suffix_min!("cba", "cba", 3);
assert_suffix_max!("cba", "c", 1);
assert_suffix_min!("abcabc", "abca", 3);
assert_suffix_max!("abcabc", "abcabc", 3);
assert_suffix_min!("abcabcabc", "abcabca", 3);
assert_suffix_max!("abcabcabc", "abcabcabc", 3);
assert_suffix_min!("abczz", "a", 1);
assert_suffix_max!("abczz", "abczz", 5);
assert_suffix_min!("zzabc", "zza", 3);
assert_suffix_max!("zzabc", "zz", 1);
assert_suffix_min!("aaa", "aaa", 1);
assert_suffix_max!("aaa", "aaa", 1);
}
#[cfg(not(miri))]
quickcheck::quickcheck! {
fn qc_suffix_forward_maximal(bytes: Vec<u8>) -> bool {
if bytes.is_empty() {
return true;
}
let (got, _) = get_suffix_forward(&bytes, SuffixKind::Maximal);
let expected = naive_maximal_suffix_forward(&bytes);
got == expected
}
fn qc_suffix_reverse_maximal(bytes: Vec<u8>) -> bool {
if bytes.is_empty() {
return true;
}
let (got, _) = get_suffix_reverse(&bytes, SuffixKind::Maximal);
let expected = naive_maximal_suffix_reverse(&bytes);
expected == got
}
}
// This is a regression test caught by quickcheck that exercised a bug in
// the reverse small period handling. The bug was that we were using 'if j
// == shift' to determine if a match occurred, but the correct guard is 'if
// j >= shift', which matches the corresponding guard in the forward impl.
#[test]
fn regression_rev_small_period() {
let rfind = |h, n| FinderRev::new(n).rfind(h, n);
let haystack = "ababaz";
let needle = "abab";
assert_eq!(Some(0), rfind(haystack.as_bytes(), needle.as_bytes()));
}
}

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/*!
This module defines "generic" routines that can be specialized to specific
architectures.
We don't expose this module primarily because it would require exposing all
of the internal infrastructure required to write these generic routines.
That infrastructure should be treated as an implementation detail so that
it is allowed to evolve. Instead, what we expose are architecture specific
instantiations of these generic implementations. The generic code just lets us
write the code once (usually).
*/
pub(crate) mod memchr;
pub(crate) mod packedpair;

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/*!
Generic crate-internal routines for the "packed pair" SIMD algorithm.
The "packed pair" algorithm is based on the [generic SIMD] algorithm. The main
difference is that it (by default) uses a background distribution of byte
frequencies to heuristically select the pair of bytes to search for.
[generic SIMD]: http://0x80.pl/articles/simd-strfind.html#first-and-last
*/
use crate::{
arch::all::{is_equal_raw, packedpair::Pair},
ext::Pointer,
vector::{MoveMask, Vector},
};
/// A generic architecture dependent "packed pair" finder.
///
/// This finder picks two bytes that it believes have high predictive power
/// for indicating an overall match of a needle. Depending on whether
/// `Finder::find` or `Finder::find_prefilter` is used, it reports offsets
/// where the needle matches or could match. In the prefilter case, candidates
/// are reported whenever the [`Pair`] of bytes given matches.
///
/// This is architecture dependent because it uses specific vector operations
/// to look for occurrences of the pair of bytes.
///
/// This type is not meant to be exported and is instead meant to be used as
/// the implementation for architecture specific facades. Why? Because it's a
/// bit of a quirky API that requires `inline(always)` annotations. And pretty
/// much everything has safety obligations due (at least) to the caller needing
/// to inline calls into routines marked with
/// `#[target_feature(enable = "...")]`.
#[derive(Clone, Copy, Debug)]
pub(crate) struct Finder<V> {
pair: Pair,
v1: V,
v2: V,
min_haystack_len: usize,
}
impl<V: Vector> Finder<V> {
/// Create a new pair searcher. The searcher returned can either report
/// exact matches of `needle` or act as a prefilter and report candidate
/// positions of `needle`.
///
/// # Safety
///
/// Callers must ensure that whatever vector type this routine is called
/// with is supported by the current environment.
///
/// Callers must also ensure that `needle.len() >= 2`.
#[inline(always)]
pub(crate) unsafe fn new(needle: &[u8], pair: Pair) -> Finder<V> {
let max_index = pair.index1().max(pair.index2());
let min_haystack_len =
core::cmp::max(needle.len(), usize::from(max_index) + V::BYTES);
let v1 = V::splat(needle[usize::from(pair.index1())]);
let v2 = V::splat(needle[usize::from(pair.index2())]);
Finder { pair, v1, v2, min_haystack_len }
}
/// Searches the given haystack for the given needle. The needle given
/// should be the same as the needle that this finder was initialized
/// with.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
///
/// # Safety
///
/// Since this is meant to be used with vector functions, callers need to
/// specialize this inside of a function with a `target_feature` attribute.
/// Therefore, callers must ensure that whatever target feature is being
/// used supports the vector functions that this function is specialized
/// for. (For the specific vector functions used, see the Vector trait
/// implementations.)
#[inline(always)]
pub(crate) unsafe fn find(
&self,
haystack: &[u8],
needle: &[u8],
) -> Option<usize> {
assert!(
haystack.len() >= self.min_haystack_len,
"haystack too small, should be at least {} but got {}",
self.min_haystack_len,
haystack.len(),
);
let all = V::Mask::all_zeros_except_least_significant(0);
let start = haystack.as_ptr();
let end = start.add(haystack.len());
let max = end.sub(self.min_haystack_len);
let mut cur = start;
// N.B. I did experiment with unrolling the loop to deal with size(V)
// bytes at a time and 2*size(V) bytes at a time. The double unroll
// was marginally faster while the quadruple unroll was unambiguously
// slower. In the end, I decided the complexity from unrolling wasn't
// worth it. I used the memmem/krate/prebuilt/huge-en/ benchmarks to
// compare.
while cur <= max {
if let Some(chunki) = self.find_in_chunk(needle, cur, end, all) {
return Some(matched(start, cur, chunki));
}
cur = cur.add(V::BYTES);
}
if cur < end {
let remaining = end.distance(cur);
debug_assert!(
remaining < self.min_haystack_len,
"remaining bytes should be smaller than the minimum haystack \
length of {}, but there are {} bytes remaining",
self.min_haystack_len,
remaining,
);
if remaining < needle.len() {
return None;
}
debug_assert!(
max < cur,
"after main loop, cur should have exceeded max",
);
let overlap = cur.distance(max);
debug_assert!(
overlap > 0,
"overlap ({}) must always be non-zero",
overlap,
);
debug_assert!(
overlap < V::BYTES,
"overlap ({}) cannot possibly be >= than a vector ({})",
overlap,
V::BYTES,
);
// The mask has all of its bits set except for the first N least
// significant bits, where N=overlap. This way, any matches that
// occur in find_in_chunk within the overlap are automatically
// ignored.
let mask = V::Mask::all_zeros_except_least_significant(overlap);
cur = max;
let m = self.find_in_chunk(needle, cur, end, mask);
if let Some(chunki) = m {
return Some(matched(start, cur, chunki));
}
}
None
}
/// Searches the given haystack for offsets that represent candidate
/// matches of the `needle` given to this finder's constructor. The offsets
/// returned, if they are a match, correspond to the starting offset of
/// `needle` in the given `haystack`.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
///
/// # Safety
///
/// Since this is meant to be used with vector functions, callers need to
/// specialize this inside of a function with a `target_feature` attribute.
/// Therefore, callers must ensure that whatever target feature is being
/// used supports the vector functions that this function is specialized
/// for. (For the specific vector functions used, see the Vector trait
/// implementations.)
#[inline(always)]
pub(crate) unsafe fn find_prefilter(
&self,
haystack: &[u8],
) -> Option<usize> {
assert!(
haystack.len() >= self.min_haystack_len,
"haystack too small, should be at least {} but got {}",
self.min_haystack_len,
haystack.len(),
);
let start = haystack.as_ptr();
let end = start.add(haystack.len());
let max = end.sub(self.min_haystack_len);
let mut cur = start;
// N.B. I did experiment with unrolling the loop to deal with size(V)
// bytes at a time and 2*size(V) bytes at a time. The double unroll
// was marginally faster while the quadruple unroll was unambiguously
// slower. In the end, I decided the complexity from unrolling wasn't
// worth it. I used the memmem/krate/prebuilt/huge-en/ benchmarks to
// compare.
while cur <= max {
if let Some(chunki) = self.find_prefilter_in_chunk(cur) {
return Some(matched(start, cur, chunki));
}
cur = cur.add(V::BYTES);
}
if cur < end {
// This routine immediately quits if a candidate match is found.
// That means that if we're here, no candidate matches have been
// found at or before 'ptr'. Thus, we don't need to mask anything
// out even though we might technically search part of the haystack
// that we've already searched (because we know it can't match).
cur = max;
if let Some(chunki) = self.find_prefilter_in_chunk(cur) {
return Some(matched(start, cur, chunki));
}
}
None
}
/// Search for an occurrence of our byte pair from the needle in the chunk
/// pointed to by cur, with the end of the haystack pointed to by end.
/// When an occurrence is found, memcmp is run to check if a match occurs
/// at the corresponding position.
///
/// `mask` should have bits set corresponding the positions in the chunk
/// in which matches are considered. This is only used for the last vector
/// load where the beginning of the vector might have overlapped with the
/// last load in the main loop. The mask lets us avoid visiting positions
/// that have already been discarded as matches.
///
/// # Safety
///
/// It must be safe to do an unaligned read of size(V) bytes starting at
/// both (cur + self.index1) and (cur + self.index2). It must also be safe
/// to do unaligned loads on cur up to (end - needle.len()).
#[inline(always)]
unsafe fn find_in_chunk(
&self,
needle: &[u8],
cur: *const u8,
end: *const u8,
mask: V::Mask,
) -> Option<usize> {
let index1 = usize::from(self.pair.index1());
let index2 = usize::from(self.pair.index2());
let chunk1 = V::load_unaligned(cur.add(index1));
let chunk2 = V::load_unaligned(cur.add(index2));
let eq1 = chunk1.cmpeq(self.v1);
let eq2 = chunk2.cmpeq(self.v2);
let mut offsets = eq1.and(eq2).movemask().and(mask);
while offsets.has_non_zero() {
let offset = offsets.first_offset();
let cur = cur.add(offset);
if end.sub(needle.len()) < cur {
return None;
}
if is_equal_raw(needle.as_ptr(), cur, needle.len()) {
return Some(offset);
}
offsets = offsets.clear_least_significant_bit();
}
None
}
/// Search for an occurrence of our byte pair from the needle in the chunk
/// pointed to by cur, with the end of the haystack pointed to by end.
/// When an occurrence is found, memcmp is run to check if a match occurs
/// at the corresponding position.
///
/// # Safety
///
/// It must be safe to do an unaligned read of size(V) bytes starting at
/// both (cur + self.index1) and (cur + self.index2). It must also be safe
/// to do unaligned reads on cur up to (end - needle.len()).
#[inline(always)]
unsafe fn find_prefilter_in_chunk(&self, cur: *const u8) -> Option<usize> {
let index1 = usize::from(self.pair.index1());
let index2 = usize::from(self.pair.index2());
let chunk1 = V::load_unaligned(cur.add(index1));
let chunk2 = V::load_unaligned(cur.add(index2));
let eq1 = chunk1.cmpeq(self.v1);
let eq2 = chunk2.cmpeq(self.v2);
let offsets = eq1.and(eq2).movemask();
if !offsets.has_non_zero() {
return None;
}
Some(offsets.first_offset())
}
/// Returns the pair of offsets (into the needle) used to check as a
/// predicate before confirming whether a needle exists at a particular
/// position.
#[inline]
pub(crate) fn pair(&self) -> &Pair {
&self.pair
}
/// Returns the minimum haystack length that this `Finder` can search.
///
/// Providing a haystack to this `Finder` shorter than this length is
/// guaranteed to result in a panic.
#[inline(always)]
pub(crate) fn min_haystack_len(&self) -> usize {
self.min_haystack_len
}
}
/// Accepts a chunk-relative offset and returns a haystack relative offset.
///
/// This used to be marked `#[cold]` and `#[inline(never)]`, but I couldn't
/// observe a consistent measureable difference between that and just inlining
/// it. So we go with inlining it.
///
/// # Safety
///
/// Same at `ptr::offset_from` in addition to `cur >= start`.
#[inline(always)]
unsafe fn matched(start: *const u8, cur: *const u8, chunki: usize) -> usize {
cur.distance(start) + chunki
}
// If you're looking for tests, those are run for each instantiation of the
// above code. So for example, see arch::x86_64::sse2::packedpair.

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/*!
A module with low-level architecture dependent routines.
These routines are useful as primitives for tasks not covered by the higher
level crate API.
*/
pub mod all;
pub(crate) mod generic;
#[cfg(target_arch = "aarch64")]
pub mod aarch64;
#[cfg(target_arch = "wasm32")]
pub mod wasm32;
#[cfg(target_arch = "x86_64")]
pub mod x86_64;

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/*!
Wrapper routines for `memchr` and friends.
These routines choose the best implementation at compile time. (This is
different from `x86_64` because it is expected that `simd128` is almost always
available for `wasm32` targets.)
*/
macro_rules! defraw {
($ty:ident, $find:ident, $start:ident, $end:ident, $($needles:ident),+) => {{
#[cfg(target_feature = "simd128")]
{
use crate::arch::wasm32::simd128::memchr::$ty;
debug!("chose simd128 for {}", stringify!($ty));
debug_assert!($ty::is_available());
// SAFETY: We know that wasm memchr is always available whenever
// code is compiled for `wasm32` with the `simd128` target feature
// enabled.
$ty::new_unchecked($($needles),+).$find($start, $end)
}
#[cfg(not(target_feature = "simd128"))]
{
use crate::arch::all::memchr::$ty;
debug!(
"no simd128 feature available, using fallback for {}",
stringify!($ty),
);
$ty::new($($needles),+).$find($start, $end)
}
}}
}
/// memchr, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::find_raw`.
#[inline(always)]
pub(crate) unsafe fn memchr_raw(
n1: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(One, find_raw, start, end, n1)
}
/// memrchr, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::rfind_raw`.
#[inline(always)]
pub(crate) unsafe fn memrchr_raw(
n1: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(One, rfind_raw, start, end, n1)
}
/// memchr2, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Two::find_raw`.
#[inline(always)]
pub(crate) unsafe fn memchr2_raw(
n1: u8,
n2: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(Two, find_raw, start, end, n1, n2)
}
/// memrchr2, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Two::rfind_raw`.
#[inline(always)]
pub(crate) unsafe fn memrchr2_raw(
n1: u8,
n2: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(Two, rfind_raw, start, end, n1, n2)
}
/// memchr3, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Three::find_raw`.
#[inline(always)]
pub(crate) unsafe fn memchr3_raw(
n1: u8,
n2: u8,
n3: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(Three, find_raw, start, end, n1, n2, n3)
}
/// memrchr3, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Three::rfind_raw`.
#[inline(always)]
pub(crate) unsafe fn memrchr3_raw(
n1: u8,
n2: u8,
n3: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
defraw!(Three, rfind_raw, start, end, n1, n2, n3)
}
/// Count all matching bytes, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::count_raw`.
#[inline(always)]
pub(crate) unsafe fn count_raw(
n1: u8,
start: *const u8,
end: *const u8,
) -> usize {
defraw!(One, count_raw, start, end, n1)
}

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/*!
Vector algorithms for the `wasm32` target.
*/
pub mod simd128;
pub(crate) mod memchr;

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/*!
Algorithms for the `wasm32` target using 128-bit vectors via simd128.
*/
pub mod memchr;
pub mod packedpair;

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/*!
A 128-bit vector implementation of the "packed pair" SIMD algorithm.
The "packed pair" algorithm is based on the [generic SIMD] algorithm. The main
difference is that it (by default) uses a background distribution of byte
frequencies to heuristically select the pair of bytes to search for.
[generic SIMD]: http://0x80.pl/articles/simd-strfind.html#first-and-last
*/
use core::arch::wasm32::v128;
use crate::arch::{all::packedpair::Pair, generic::packedpair};
/// A "packed pair" finder that uses 128-bit vector operations.
///
/// This finder picks two bytes that it believes have high predictive power
/// for indicating an overall match of a needle. Depending on whether
/// `Finder::find` or `Finder::find_prefilter` is used, it reports offsets
/// where the needle matches or could match. In the prefilter case, candidates
/// are reported whenever the [`Pair`] of bytes given matches.
#[derive(Clone, Copy, Debug)]
pub struct Finder(packedpair::Finder<v128>);
impl Finder {
/// Create a new pair searcher. The searcher returned can either report
/// exact matches of `needle` or act as a prefilter and report candidate
/// positions of `needle`.
///
/// If simd128 is unavailable in the current environment or if a [`Pair`]
/// could not be constructed from the needle given, then `None` is
/// returned.
#[inline]
pub fn new(needle: &[u8]) -> Option<Finder> {
Finder::with_pair(needle, Pair::new(needle)?)
}
/// Create a new "packed pair" finder using the pair of bytes given.
///
/// This constructor permits callers to control precisely which pair of
/// bytes is used as a predicate.
///
/// If simd128 is unavailable in the current environment, then `None` is
/// returned.
#[inline]
pub fn with_pair(needle: &[u8], pair: Pair) -> Option<Finder> {
if Finder::is_available() {
// SAFETY: we check that simd128 is available above. We are also
// guaranteed to have needle.len() > 1 because we have a valid
// Pair.
unsafe { Some(Finder::with_pair_impl(needle, pair)) }
} else {
None
}
}
/// Create a new `Finder` specific to simd128 vectors and routines.
///
/// # Safety
///
/// Same as the safety for `packedpair::Finder::new`, and callers must also
/// ensure that simd128 is available.
#[target_feature(enable = "simd128")]
#[inline]
unsafe fn with_pair_impl(needle: &[u8], pair: Pair) -> Finder {
let finder = packedpair::Finder::<v128>::new(needle, pair);
Finder(finder)
}
/// Returns true when this implementation is available in the current
/// environment.
///
/// When this is true, it is guaranteed that [`Finder::with_pair`] will
/// return a `Some` value. Similarly, when it is false, it is guaranteed
/// that `Finder::with_pair` will return a `None` value. Notice that this
/// does not guarantee that [`Finder::new`] will return a `Finder`. Namely,
/// even when `Finder::is_available` is true, it is not guaranteed that a
/// valid [`Pair`] can be found from the needle given.
///
/// Note also that for the lifetime of a single program, if this returns
/// true then it will always return true.
#[inline]
pub fn is_available() -> bool {
#[cfg(target_feature = "simd128")]
{
true
}
#[cfg(not(target_feature = "simd128"))]
{
false
}
}
/// Execute a search using wasm32 v128 vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
#[inline]
pub fn find(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
self.find_impl(haystack, needle)
}
/// Execute a search using wasm32 v128 vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
#[inline]
pub fn find_prefilter(&self, haystack: &[u8]) -> Option<usize> {
self.find_prefilter_impl(haystack)
}
/// Execute a search using wasm32 v128 vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
///
/// # Safety
///
/// (The target feature safety obligation is automatically fulfilled by
/// virtue of being a method on `Finder`, which can only be constructed
/// when it is safe to call `simd128` routines.)
#[target_feature(enable = "simd128")]
#[inline]
fn find_impl(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
// SAFETY: The target feature safety obligation is automatically
// fulfilled by virtue of being a method on `Finder`, which can only be
// constructed when it is safe to call `simd128` routines.
unsafe { self.0.find(haystack, needle) }
}
/// Execute a prefilter search using wasm32 v128 vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
///
/// # Safety
///
/// (The target feature safety obligation is automatically fulfilled by
/// virtue of being a method on `Finder`, which can only be constructed
/// when it is safe to call `simd128` routines.)
#[target_feature(enable = "simd128")]
#[inline]
fn find_prefilter_impl(&self, haystack: &[u8]) -> Option<usize> {
// SAFETY: The target feature safety obligation is automatically
// fulfilled by virtue of being a method on `Finder`, which can only be
// constructed when it is safe to call `simd128` routines.
unsafe { self.0.find_prefilter(haystack) }
}
/// Returns the pair of offsets (into the needle) used to check as a
/// predicate before confirming whether a needle exists at a particular
/// position.
#[inline]
pub fn pair(&self) -> &Pair {
self.0.pair()
}
/// Returns the minimum haystack length that this `Finder` can search.
///
/// Using a haystack with length smaller than this in a search will result
/// in a panic. The reason for this restriction is that this finder is
/// meant to be a low-level component that is part of a larger substring
/// strategy. In that sense, it avoids trying to handle all cases and
/// instead only handles the cases that it can handle very well.
#[inline]
pub fn min_haystack_len(&self) -> usize {
self.0.min_haystack_len()
}
}
#[cfg(test)]
mod tests {
use super::*;
fn find(haystack: &[u8], needle: &[u8]) -> Option<Option<usize>> {
let f = Finder::new(needle)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find(haystack, needle))
}
define_substring_forward_quickcheck!(find);
#[test]
fn forward_substring() {
crate::tests::substring::Runner::new().fwd(find).run()
}
#[test]
fn forward_packedpair() {
fn find(
haystack: &[u8],
needle: &[u8],
index1: u8,
index2: u8,
) -> Option<Option<usize>> {
let pair = Pair::with_indices(needle, index1, index2)?;
let f = Finder::with_pair(needle, pair)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find(haystack, needle))
}
crate::tests::packedpair::Runner::new().fwd(find).run()
}
#[test]
fn forward_packedpair_prefilter() {
fn find(
haystack: &[u8],
needle: &[u8],
index1: u8,
index2: u8,
) -> Option<Option<usize>> {
let pair = Pair::with_indices(needle, index1, index2)?;
let f = Finder::with_pair(needle, pair)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find_prefilter(haystack))
}
crate::tests::packedpair::Runner::new().fwd(find).run()
}
}

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/*!
Algorithms for the `x86_64` target using 256-bit vectors via AVX2.
*/
pub mod memchr;
pub mod packedpair;

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/*!
A 256-bit vector implementation of the "packed pair" SIMD algorithm.
The "packed pair" algorithm is based on the [generic SIMD] algorithm. The main
difference is that it (by default) uses a background distribution of byte
frequencies to heuristically select the pair of bytes to search for.
[generic SIMD]: http://0x80.pl/articles/simd-strfind.html#first-and-last
*/
use core::arch::x86_64::{__m128i, __m256i};
use crate::arch::{all::packedpair::Pair, generic::packedpair};
/// A "packed pair" finder that uses 256-bit vector operations.
///
/// This finder picks two bytes that it believes have high predictive power
/// for indicating an overall match of a needle. Depending on whether
/// `Finder::find` or `Finder::find_prefilter` is used, it reports offsets
/// where the needle matches or could match. In the prefilter case, candidates
/// are reported whenever the [`Pair`] of bytes given matches.
#[derive(Clone, Copy, Debug)]
pub struct Finder {
sse2: packedpair::Finder<__m128i>,
avx2: packedpair::Finder<__m256i>,
}
impl Finder {
/// Create a new pair searcher. The searcher returned can either report
/// exact matches of `needle` or act as a prefilter and report candidate
/// positions of `needle`.
///
/// If AVX2 is unavailable in the current environment or if a [`Pair`]
/// could not be constructed from the needle given, then `None` is
/// returned.
#[inline]
pub fn new(needle: &[u8]) -> Option<Finder> {
Finder::with_pair(needle, Pair::new(needle)?)
}
/// Create a new "packed pair" finder using the pair of bytes given.
///
/// This constructor permits callers to control precisely which pair of
/// bytes is used as a predicate.
///
/// If AVX2 is unavailable in the current environment, then `None` is
/// returned.
#[inline]
pub fn with_pair(needle: &[u8], pair: Pair) -> Option<Finder> {
if Finder::is_available() {
// SAFETY: we check that sse2/avx2 is available above. We are also
// guaranteed to have needle.len() > 1 because we have a valid
// Pair.
unsafe { Some(Finder::with_pair_impl(needle, pair)) }
} else {
None
}
}
/// Create a new `Finder` specific to SSE2 vectors and routines.
///
/// # Safety
///
/// Same as the safety for `packedpair::Finder::new`, and callers must also
/// ensure that both SSE2 and AVX2 are available.
#[target_feature(enable = "sse2", enable = "avx2")]
#[inline]
unsafe fn with_pair_impl(needle: &[u8], pair: Pair) -> Finder {
let sse2 = packedpair::Finder::<__m128i>::new(needle, pair);
let avx2 = packedpair::Finder::<__m256i>::new(needle, pair);
Finder { sse2, avx2 }
}
/// Returns true when this implementation is available in the current
/// environment.
///
/// When this is true, it is guaranteed that [`Finder::with_pair`] will
/// return a `Some` value. Similarly, when it is false, it is guaranteed
/// that `Finder::with_pair` will return a `None` value. Notice that this
/// does not guarantee that [`Finder::new`] will return a `Finder`. Namely,
/// even when `Finder::is_available` is true, it is not guaranteed that a
/// valid [`Pair`] can be found from the needle given.
///
/// Note also that for the lifetime of a single program, if this returns
/// true then it will always return true.
#[inline]
pub fn is_available() -> bool {
#[cfg(not(target_feature = "sse2"))]
{
false
}
#[cfg(target_feature = "sse2")]
{
#[cfg(target_feature = "avx2")]
{
true
}
#[cfg(not(target_feature = "avx2"))]
{
#[cfg(feature = "std")]
{
std::is_x86_feature_detected!("avx2")
}
#[cfg(not(feature = "std"))]
{
false
}
}
}
}
/// Execute a search using AVX2 vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
#[inline]
pub fn find(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
// SAFETY: Building a `Finder` means it's safe to call 'sse2' routines.
unsafe { self.find_impl(haystack, needle) }
}
/// Run this finder on the given haystack as a prefilter.
///
/// If a candidate match is found, then an offset where the needle *could*
/// begin in the haystack is returned.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
#[inline]
pub fn find_prefilter(&self, haystack: &[u8]) -> Option<usize> {
// SAFETY: Building a `Finder` means it's safe to call 'sse2' routines.
unsafe { self.find_prefilter_impl(haystack) }
}
/// Execute a search using AVX2 vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
///
/// # Safety
///
/// (The target feature safety obligation is automatically fulfilled by
/// virtue of being a method on `Finder`, which can only be constructed
/// when it is safe to call `sse2` and `avx2` routines.)
#[target_feature(enable = "sse2", enable = "avx2")]
#[inline]
unsafe fn find_impl(
&self,
haystack: &[u8],
needle: &[u8],
) -> Option<usize> {
if haystack.len() < self.avx2.min_haystack_len() {
self.sse2.find(haystack, needle)
} else {
self.avx2.find(haystack, needle)
}
}
/// Execute a prefilter search using AVX2 vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
///
/// # Safety
///
/// (The target feature safety obligation is automatically fulfilled by
/// virtue of being a method on `Finder`, which can only be constructed
/// when it is safe to call `sse2` and `avx2` routines.)
#[target_feature(enable = "sse2", enable = "avx2")]
#[inline]
unsafe fn find_prefilter_impl(&self, haystack: &[u8]) -> Option<usize> {
if haystack.len() < self.avx2.min_haystack_len() {
self.sse2.find_prefilter(haystack)
} else {
self.avx2.find_prefilter(haystack)
}
}
/// Returns the pair of offsets (into the needle) used to check as a
/// predicate before confirming whether a needle exists at a particular
/// position.
#[inline]
pub fn pair(&self) -> &Pair {
self.avx2.pair()
}
/// Returns the minimum haystack length that this `Finder` can search.
///
/// Using a haystack with length smaller than this in a search will result
/// in a panic. The reason for this restriction is that this finder is
/// meant to be a low-level component that is part of a larger substring
/// strategy. In that sense, it avoids trying to handle all cases and
/// instead only handles the cases that it can handle very well.
#[inline]
pub fn min_haystack_len(&self) -> usize {
// The caller doesn't need to care about AVX2's min_haystack_len
// since this implementation will automatically switch to the SSE2
// implementation if the haystack is too short for AVX2. Therefore, the
// caller only needs to care about SSE2's min_haystack_len.
//
// This does assume that SSE2's min_haystack_len is less than or
// equal to AVX2's min_haystack_len. In practice, this is true and
// there is no way it could be false based on how this Finder is
// implemented. Namely, both SSE2 and AVX2 use the same `Pair`. If
// they used different pairs, then it's possible (although perhaps
// pathological) for SSE2's min_haystack_len to be bigger than AVX2's.
self.sse2.min_haystack_len()
}
}
#[cfg(test)]
mod tests {
use super::*;
fn find(haystack: &[u8], needle: &[u8]) -> Option<Option<usize>> {
let f = Finder::new(needle)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find(haystack, needle))
}
define_substring_forward_quickcheck!(find);
#[test]
fn forward_substring() {
crate::tests::substring::Runner::new().fwd(find).run()
}
#[test]
fn forward_packedpair() {
fn find(
haystack: &[u8],
needle: &[u8],
index1: u8,
index2: u8,
) -> Option<Option<usize>> {
let pair = Pair::with_indices(needle, index1, index2)?;
let f = Finder::with_pair(needle, pair)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find(haystack, needle))
}
crate::tests::packedpair::Runner::new().fwd(find).run()
}
#[test]
fn forward_packedpair_prefilter() {
fn find(
haystack: &[u8],
needle: &[u8],
index1: u8,
index2: u8,
) -> Option<Option<usize>> {
if !cfg!(target_feature = "sse2") {
return None;
}
let pair = Pair::with_indices(needle, index1, index2)?;
let f = Finder::with_pair(needle, pair)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find_prefilter(haystack))
}
crate::tests::packedpair::Runner::new().fwd(find).run()
}
}

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/*!
Wrapper routines for `memchr` and friends.
These routines efficiently dispatch to the best implementation based on what
the CPU supports.
*/
/// Provides a way to run a memchr-like function while amortizing the cost of
/// runtime CPU feature detection.
///
/// This works by loading a function pointer from an atomic global. Initially,
/// this global is set to a function that does CPU feature detection. For
/// example, if AVX2 is enabled, then the AVX2 implementation is used.
/// Otherwise, at least on x86_64, the SSE2 implementation is used. (And
/// in some niche cases, if SSE2 isn't available, then the architecture
/// independent fallback implementation is used.)
///
/// After the first call to this function, the atomic global is replaced with
/// the specific AVX2, SSE2 or fallback routine chosen. Subsequent calls then
/// will directly call the chosen routine instead of needing to go through the
/// CPU feature detection branching again.
///
/// This particular macro is specifically written to provide the implementation
/// of functions with the following signature:
///
/// ```ignore
/// fn memchr(needle1: u8, start: *const u8, end: *const u8) -> Option<usize>;
/// ```
///
/// Where you can also have `memchr2` and `memchr3`, but with `needle2` and
/// `needle3`, respectively. The `start` and `end` parameters correspond to the
/// start and end of the haystack, respectively.
///
/// We use raw pointers here instead of the more obvious `haystack: &[u8]` so
/// that the function is compatible with our lower level iterator logic that
/// operates on raw pointers. We use this macro to implement "raw" memchr
/// routines with the signature above, and then define memchr routines using
/// regular slices on top of them.
///
/// Note that we use `#[cfg(target_feature = "sse2")]` below even though
/// it shouldn't be strictly necessary because without it, it seems to
/// cause the compiler to blow up. I guess it can't handle a function
/// pointer being created with a sse target feature? Dunno. See the
/// `build-for-x86-64-but-non-sse-target` CI job if you want to experiment with
/// this.
///
/// # Safety
///
/// Primarily callers must that `$fnty` is a correct function pointer type and
/// not something else.
///
/// Callers must also ensure that `$memchrty::$memchrfind` corresponds to a
/// routine that returns a valid function pointer when a match is found. That
/// is, a pointer that is `>= start` and `< end`.
///
/// Callers must also ensure that the `$hay_start` and `$hay_end` identifiers
/// correspond to valid pointers.
macro_rules! unsafe_ifunc {
(
$memchrty:ident,
$memchrfind:ident,
$fnty:ty,
$retty:ty,
$hay_start:ident,
$hay_end:ident,
$($needle:ident),+
) => {{
#![allow(unused_unsafe)]
use core::sync::atomic::{AtomicPtr, Ordering};
type Fn = *mut ();
type RealFn = $fnty;
static FN: AtomicPtr<()> = AtomicPtr::new(detect as Fn);
#[cfg(target_feature = "sse2")]
#[target_feature(enable = "sse2", enable = "avx2")]
unsafe fn find_avx2(
$($needle: u8),+,
$hay_start: *const u8,
$hay_end: *const u8,
) -> $retty {
use crate::arch::x86_64::avx2::memchr::$memchrty;
$memchrty::new_unchecked($($needle),+)
.$memchrfind($hay_start, $hay_end)
}
#[cfg(target_feature = "sse2")]
#[target_feature(enable = "sse2")]
unsafe fn find_sse2(
$($needle: u8),+,
$hay_start: *const u8,
$hay_end: *const u8,
) -> $retty {
use crate::arch::x86_64::sse2::memchr::$memchrty;
$memchrty::new_unchecked($($needle),+)
.$memchrfind($hay_start, $hay_end)
}
unsafe fn find_fallback(
$($needle: u8),+,
$hay_start: *const u8,
$hay_end: *const u8,
) -> $retty {
use crate::arch::all::memchr::$memchrty;
$memchrty::new($($needle),+).$memchrfind($hay_start, $hay_end)
}
unsafe fn detect(
$($needle: u8),+,
$hay_start: *const u8,
$hay_end: *const u8,
) -> $retty {
let fun = {
#[cfg(not(target_feature = "sse2"))]
{
debug!(
"no sse2 feature available, using fallback for {}",
stringify!($memchrty),
);
find_fallback as RealFn
}
#[cfg(target_feature = "sse2")]
{
use crate::arch::x86_64::{sse2, avx2};
if avx2::memchr::$memchrty::is_available() {
debug!("chose AVX2 for {}", stringify!($memchrty));
find_avx2 as RealFn
} else if sse2::memchr::$memchrty::is_available() {
debug!("chose SSE2 for {}", stringify!($memchrty));
find_sse2 as RealFn
} else {
debug!("chose fallback for {}", stringify!($memchrty));
find_fallback as RealFn
}
}
};
FN.store(fun as Fn, Ordering::Relaxed);
// SAFETY: The only thing we need to uphold here is the
// `#[target_feature]` requirements. Since we check is_available
// above before using the corresponding implementation, we are
// guaranteed to only call code that is supported on the current
// CPU.
fun($($needle),+, $hay_start, $hay_end)
}
// SAFETY: By virtue of the caller contract, RealFn is a function
// pointer, which is always safe to transmute with a *mut (). Also,
// since we use $memchrty::is_available, it is guaranteed to be safe
// to call $memchrty::$memchrfind.
unsafe {
let fun = FN.load(Ordering::Relaxed);
core::mem::transmute::<Fn, RealFn>(fun)(
$($needle),+,
$hay_start,
$hay_end,
)
}
}};
}
// The routines below dispatch to AVX2, SSE2 or a fallback routine based on
// what's available in the current environment. The secret sauce here is that
// we only check for which one to use approximately once, and then "cache" that
// choice into a global function pointer. Subsequent invocations then just call
// the appropriate function directly.
/// memchr, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::find_raw`.
#[inline(always)]
pub(crate) fn memchr_raw(
n1: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
// SAFETY: We provide a valid function pointer type.
unsafe_ifunc!(
One,
find_raw,
unsafe fn(u8, *const u8, *const u8) -> Option<*const u8>,
Option<*const u8>,
start,
end,
n1
)
}
/// memrchr, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::rfind_raw`.
#[inline(always)]
pub(crate) fn memrchr_raw(
n1: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
// SAFETY: We provide a valid function pointer type.
unsafe_ifunc!(
One,
rfind_raw,
unsafe fn(u8, *const u8, *const u8) -> Option<*const u8>,
Option<*const u8>,
start,
end,
n1
)
}
/// memchr2, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Two::find_raw`.
#[inline(always)]
pub(crate) fn memchr2_raw(
n1: u8,
n2: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
// SAFETY: We provide a valid function pointer type.
unsafe_ifunc!(
Two,
find_raw,
unsafe fn(u8, u8, *const u8, *const u8) -> Option<*const u8>,
Option<*const u8>,
start,
end,
n1,
n2
)
}
/// memrchr2, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Two::rfind_raw`.
#[inline(always)]
pub(crate) fn memrchr2_raw(
n1: u8,
n2: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
// SAFETY: We provide a valid function pointer type.
unsafe_ifunc!(
Two,
rfind_raw,
unsafe fn(u8, u8, *const u8, *const u8) -> Option<*const u8>,
Option<*const u8>,
start,
end,
n1,
n2
)
}
/// memchr3, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Three::find_raw`.
#[inline(always)]
pub(crate) fn memchr3_raw(
n1: u8,
n2: u8,
n3: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
// SAFETY: We provide a valid function pointer type.
unsafe_ifunc!(
Three,
find_raw,
unsafe fn(u8, u8, u8, *const u8, *const u8) -> Option<*const u8>,
Option<*const u8>,
start,
end,
n1,
n2,
n3
)
}
/// memrchr3, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Three::rfind_raw`.
#[inline(always)]
pub(crate) fn memrchr3_raw(
n1: u8,
n2: u8,
n3: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
// SAFETY: We provide a valid function pointer type.
unsafe_ifunc!(
Three,
rfind_raw,
unsafe fn(u8, u8, u8, *const u8, *const u8) -> Option<*const u8>,
Option<*const u8>,
start,
end,
n1,
n2,
n3
)
}
/// Count all matching bytes, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::count_raw`.
#[inline(always)]
pub(crate) fn count_raw(n1: u8, start: *const u8, end: *const u8) -> usize {
// SAFETY: We provide a valid function pointer type.
unsafe_ifunc!(
One,
count_raw,
unsafe fn(u8, *const u8, *const u8) -> usize,
usize,
start,
end,
n1
)
}

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/*!
Vector algorithms for the `x86_64` target.
*/
pub mod avx2;
pub mod sse2;
pub(crate) mod memchr;

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/*!
Algorithms for the `x86_64` target using 128-bit vectors via SSE2.
*/
pub mod memchr;
pub mod packedpair;

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/*!
A 128-bit vector implementation of the "packed pair" SIMD algorithm.
The "packed pair" algorithm is based on the [generic SIMD] algorithm. The main
difference is that it (by default) uses a background distribution of byte
frequencies to heuristically select the pair of bytes to search for.
[generic SIMD]: http://0x80.pl/articles/simd-strfind.html#first-and-last
*/
use core::arch::x86_64::__m128i;
use crate::arch::{all::packedpair::Pair, generic::packedpair};
/// A "packed pair" finder that uses 128-bit vector operations.
///
/// This finder picks two bytes that it believes have high predictive power
/// for indicating an overall match of a needle. Depending on whether
/// `Finder::find` or `Finder::find_prefilter` is used, it reports offsets
/// where the needle matches or could match. In the prefilter case, candidates
/// are reported whenever the [`Pair`] of bytes given matches.
#[derive(Clone, Copy, Debug)]
pub struct Finder(packedpair::Finder<__m128i>);
impl Finder {
/// Create a new pair searcher. The searcher returned can either report
/// exact matches of `needle` or act as a prefilter and report candidate
/// positions of `needle`.
///
/// If SSE2 is unavailable in the current environment or if a [`Pair`]
/// could not be constructed from the needle given, then `None` is
/// returned.
#[inline]
pub fn new(needle: &[u8]) -> Option<Finder> {
Finder::with_pair(needle, Pair::new(needle)?)
}
/// Create a new "packed pair" finder using the pair of bytes given.
///
/// This constructor permits callers to control precisely which pair of
/// bytes is used as a predicate.
///
/// If SSE2 is unavailable in the current environment, then `None` is
/// returned.
#[inline]
pub fn with_pair(needle: &[u8], pair: Pair) -> Option<Finder> {
if Finder::is_available() {
// SAFETY: we check that sse2 is available above. We are also
// guaranteed to have needle.len() > 1 because we have a valid
// Pair.
unsafe { Some(Finder::with_pair_impl(needle, pair)) }
} else {
None
}
}
/// Create a new `Finder` specific to SSE2 vectors and routines.
///
/// # Safety
///
/// Same as the safety for `packedpair::Finder::new`, and callers must also
/// ensure that SSE2 is available.
#[target_feature(enable = "sse2")]
#[inline]
unsafe fn with_pair_impl(needle: &[u8], pair: Pair) -> Finder {
let finder = packedpair::Finder::<__m128i>::new(needle, pair);
Finder(finder)
}
/// Returns true when this implementation is available in the current
/// environment.
///
/// When this is true, it is guaranteed that [`Finder::with_pair`] will
/// return a `Some` value. Similarly, when it is false, it is guaranteed
/// that `Finder::with_pair` will return a `None` value. Notice that this
/// does not guarantee that [`Finder::new`] will return a `Finder`. Namely,
/// even when `Finder::is_available` is true, it is not guaranteed that a
/// valid [`Pair`] can be found from the needle given.
///
/// Note also that for the lifetime of a single program, if this returns
/// true then it will always return true.
#[inline]
pub fn is_available() -> bool {
#[cfg(not(target_feature = "sse2"))]
{
false
}
#[cfg(target_feature = "sse2")]
{
true
}
}
/// Execute a search using SSE2 vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
#[inline]
pub fn find(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
// SAFETY: Building a `Finder` means it's safe to call 'sse2' routines.
unsafe { self.find_impl(haystack, needle) }
}
/// Run this finder on the given haystack as a prefilter.
///
/// If a candidate match is found, then an offset where the needle *could*
/// begin in the haystack is returned.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
#[inline]
pub fn find_prefilter(&self, haystack: &[u8]) -> Option<usize> {
// SAFETY: Building a `Finder` means it's safe to call 'sse2' routines.
unsafe { self.find_prefilter_impl(haystack) }
}
/// Execute a search using SSE2 vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
///
/// # Safety
///
/// (The target feature safety obligation is automatically fulfilled by
/// virtue of being a method on `Finder`, which can only be constructed
/// when it is safe to call `sse2` routines.)
#[target_feature(enable = "sse2")]
#[inline]
unsafe fn find_impl(
&self,
haystack: &[u8],
needle: &[u8],
) -> Option<usize> {
self.0.find(haystack, needle)
}
/// Execute a prefilter search using SSE2 vectors and routines.
///
/// # Panics
///
/// When `haystack.len()` is less than [`Finder::min_haystack_len`].
///
/// # Safety
///
/// (The target feature safety obligation is automatically fulfilled by
/// virtue of being a method on `Finder`, which can only be constructed
/// when it is safe to call `sse2` routines.)
#[target_feature(enable = "sse2")]
#[inline]
unsafe fn find_prefilter_impl(&self, haystack: &[u8]) -> Option<usize> {
self.0.find_prefilter(haystack)
}
/// Returns the pair of offsets (into the needle) used to check as a
/// predicate before confirming whether a needle exists at a particular
/// position.
#[inline]
pub fn pair(&self) -> &Pair {
self.0.pair()
}
/// Returns the minimum haystack length that this `Finder` can search.
///
/// Using a haystack with length smaller than this in a search will result
/// in a panic. The reason for this restriction is that this finder is
/// meant to be a low-level component that is part of a larger substring
/// strategy. In that sense, it avoids trying to handle all cases and
/// instead only handles the cases that it can handle very well.
#[inline]
pub fn min_haystack_len(&self) -> usize {
self.0.min_haystack_len()
}
}
#[cfg(test)]
mod tests {
use super::*;
fn find(haystack: &[u8], needle: &[u8]) -> Option<Option<usize>> {
let f = Finder::new(needle)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find(haystack, needle))
}
define_substring_forward_quickcheck!(find);
#[test]
fn forward_substring() {
crate::tests::substring::Runner::new().fwd(find).run()
}
#[test]
fn forward_packedpair() {
fn find(
haystack: &[u8],
needle: &[u8],
index1: u8,
index2: u8,
) -> Option<Option<usize>> {
let pair = Pair::with_indices(needle, index1, index2)?;
let f = Finder::with_pair(needle, pair)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find(haystack, needle))
}
crate::tests::packedpair::Runner::new().fwd(find).run()
}
#[test]
fn forward_packedpair_prefilter() {
fn find(
haystack: &[u8],
needle: &[u8],
index1: u8,
index2: u8,
) -> Option<Option<usize>> {
let pair = Pair::with_indices(needle, index1, index2)?;
let f = Finder::with_pair(needle, pair)?;
if haystack.len() < f.min_haystack_len() {
return None;
}
Some(f.find_prefilter(haystack))
}
crate::tests::packedpair::Runner::new().fwd(find).run()
}
}

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use core::ops;
/// A specialized copy-on-write byte string.
///
/// The purpose of this type is to permit usage of a "borrowed or owned
/// byte string" in a way that keeps std/no-std compatibility. That is, in
/// no-std/alloc mode, this type devolves into a simple &[u8] with no owned
/// variant available. We can't just use a plain Cow because Cow is not in
/// core.
#[derive(Clone, Debug)]
pub struct CowBytes<'a>(Imp<'a>);
// N.B. We don't use alloc::borrow::Cow here since we can get away with a
// Box<[u8]> for our use case, which is 1/3 smaller than the Vec<u8> that
// a Cow<[u8]> would use.
#[cfg(feature = "alloc")]
#[derive(Clone, Debug)]
enum Imp<'a> {
Borrowed(&'a [u8]),
Owned(alloc::boxed::Box<[u8]>),
}
#[cfg(not(feature = "alloc"))]
#[derive(Clone, Debug)]
struct Imp<'a>(&'a [u8]);
impl<'a> ops::Deref for CowBytes<'a> {
type Target = [u8];
#[inline(always)]
fn deref(&self) -> &[u8] {
self.as_slice()
}
}
impl<'a> CowBytes<'a> {
/// Create a new borrowed CowBytes.
#[inline(always)]
pub(crate) fn new<B: ?Sized + AsRef<[u8]>>(bytes: &'a B) -> CowBytes<'a> {
CowBytes(Imp::new(bytes.as_ref()))
}
/// Create a new owned CowBytes.
#[cfg(feature = "alloc")]
#[inline(always)]
fn new_owned(bytes: alloc::boxed::Box<[u8]>) -> CowBytes<'static> {
CowBytes(Imp::Owned(bytes))
}
/// Return a borrowed byte string, regardless of whether this is an owned
/// or borrowed byte string internally.
#[inline(always)]
pub(crate) fn as_slice(&self) -> &[u8] {
self.0.as_slice()
}
/// Return an owned version of this copy-on-write byte string.
///
/// If this is already an owned byte string internally, then this is a
/// no-op. Otherwise, the internal byte string is copied.
#[cfg(feature = "alloc")]
#[inline(always)]
pub(crate) fn into_owned(self) -> CowBytes<'static> {
match self.0 {
Imp::Borrowed(b) => {
CowBytes::new_owned(alloc::boxed::Box::from(b))
}
Imp::Owned(b) => CowBytes::new_owned(b),
}
}
}
impl<'a> Imp<'a> {
#[inline(always)]
pub fn new(bytes: &'a [u8]) -> Imp<'a> {
#[cfg(feature = "alloc")]
{
Imp::Borrowed(bytes)
}
#[cfg(not(feature = "alloc"))]
{
Imp(bytes)
}
}
#[cfg(feature = "alloc")]
#[inline(always)]
pub fn as_slice(&self) -> &[u8] {
#[cfg(feature = "alloc")]
{
match self {
Imp::Owned(ref x) => x,
Imp::Borrowed(x) => x,
}
}
#[cfg(not(feature = "alloc"))]
{
self.0
}
}
#[cfg(not(feature = "alloc"))]
#[inline(always)]
pub fn as_slice(&self) -> &[u8] {
self.0
}
}

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/// A trait for adding some helper routines to pointers.
pub(crate) trait Pointer {
/// Returns the distance, in units of `T`, between `self` and `origin`.
///
/// # Safety
///
/// Same as `ptr::offset_from` in addition to `self >= origin`.
unsafe fn distance(self, origin: Self) -> usize;
/// Casts this pointer to `usize`.
///
/// Callers should not convert the `usize` back to a pointer if at all
/// possible. (And if you believe it's necessary, open an issue to discuss
/// why. Otherwise, it has the potential to violate pointer provenance.)
/// The purpose of this function is just to be able to do arithmetic, i.e.,
/// computing offsets or alignments.
fn as_usize(self) -> usize;
}
impl<T> Pointer for *const T {
unsafe fn distance(self, origin: *const T) -> usize {
// TODO: Replace with `ptr::sub_ptr` once stabilized.
usize::try_from(self.offset_from(origin)).unwrap_unchecked()
}
fn as_usize(self) -> usize {
self as usize
}
}
impl<T> Pointer for *mut T {
unsafe fn distance(self, origin: *mut T) -> usize {
(self as *const T).distance(origin as *const T)
}
fn as_usize(self) -> usize {
(self as *const T).as_usize()
}
}
/// A trait for adding some helper routines to raw bytes.
pub(crate) trait Byte {
/// Converts this byte to a `char` if it's ASCII. Otherwise panics.
fn to_char(self) -> char;
}
impl Byte for u8 {
fn to_char(self) -> char {
assert!(self.is_ascii());
char::from(self)
}
}

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/*!
This library provides heavily optimized routines for string search primitives.
# Overview
This section gives a brief high level overview of what this crate offers.
* The top-level module provides routines for searching for 1, 2 or 3 bytes
in the forward or reverse direction. When searching for more than one byte,
positions are considered a match if the byte at that position matches any
of the bytes.
* The [`memmem`] sub-module provides forward and reverse substring search
routines.
In all such cases, routines operate on `&[u8]` without regard to encoding. This
is exactly what you want when searching either UTF-8 or arbitrary bytes.
# Example: using `memchr`
This example shows how to use `memchr` to find the first occurrence of `z` in
a haystack:
```
use memchr::memchr;
let haystack = b"foo bar baz quuz";
assert_eq!(Some(10), memchr(b'z', haystack));
```
# Example: matching one of three possible bytes
This examples shows how to use `memrchr3` to find occurrences of `a`, `b` or
`c`, starting at the end of the haystack.
```
use memchr::memchr3_iter;
let haystack = b"xyzaxyzbxyzc";
let mut it = memchr3_iter(b'a', b'b', b'c', haystack).rev();
assert_eq!(Some(11), it.next());
assert_eq!(Some(7), it.next());
assert_eq!(Some(3), it.next());
assert_eq!(None, it.next());
```
# Example: iterating over substring matches
This example shows how to use the [`memmem`] sub-module to find occurrences of
a substring in a haystack.
```
use memchr::memmem;
let haystack = b"foo bar foo baz foo";
let mut it = memmem::find_iter(haystack, "foo");
assert_eq!(Some(0), it.next());
assert_eq!(Some(8), it.next());
assert_eq!(Some(16), it.next());
assert_eq!(None, it.next());
```
# Example: repeating a search for the same needle
It may be possible for the overhead of constructing a substring searcher to be
measurable in some workloads. In cases where the same needle is used to search
many haystacks, it is possible to do construction once and thus to avoid it for
subsequent searches. This can be done with a [`memmem::Finder`]:
```
use memchr::memmem;
let finder = memmem::Finder::new("foo");
assert_eq!(Some(4), finder.find(b"baz foo quux"));
assert_eq!(None, finder.find(b"quux baz bar"));
```
# Why use this crate?
At first glance, the APIs provided by this crate might seem weird. Why provide
a dedicated routine like `memchr` for something that could be implemented
clearly and trivially in one line:
```
fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
haystack.iter().position(|&b| b == needle)
}
```
Or similarly, why does this crate provide substring search routines when Rust's
core library already provides them?
```
fn search(haystack: &str, needle: &str) -> Option<usize> {
haystack.find(needle)
}
```
The primary reason for both of them to exist is performance. When it comes to
performance, at a high level at least, there are two primary ways to look at
it:
* **Throughput**: For this, think about it as, "given some very large haystack
and a byte that never occurs in that haystack, how long does it take to
search through it and determine that it, in fact, does not occur?"
* **Latency**: For this, think about it as, "given a tiny haystack---just a
few bytes---how long does it take to determine if a byte is in it?"
The `memchr` routine in this crate has _slightly_ worse latency than the
solution presented above, however, its throughput can easily be over an
order of magnitude faster. This is a good general purpose trade off to make.
You rarely lose, but often gain big.
**NOTE:** The name `memchr` comes from the corresponding routine in `libc`. A
key advantage of using this library is that its performance is not tied to its
quality of implementation in the `libc` you happen to be using, which can vary
greatly from platform to platform.
But what about substring search? This one is a bit more complicated. The
primary reason for its existence is still indeed performance, but it's also
useful because Rust's core library doesn't actually expose any substring
search routine on arbitrary bytes. The only substring search routine that
exists works exclusively on valid UTF-8.
So if you have valid UTF-8, is there a reason to use this over the standard
library substring search routine? Yes. This routine is faster on almost every
metric, including latency. The natural question then, is why isn't this
implementation in the standard library, even if only for searching on UTF-8?
The reason is that the implementation details for using SIMD in the standard
library haven't quite been worked out yet.
**NOTE:** Currently, only `x86_64`, `wasm32` and `aarch64` targets have vector
accelerated implementations of `memchr` (and friends) and `memmem`.
# Crate features
* **std** - When enabled (the default), this will permit features specific to
the standard library. Currently, the only thing used from the standard library
is runtime SIMD CPU feature detection. This means that this feature must be
enabled to get AVX2 accelerated routines on `x86_64` targets without enabling
the `avx2` feature at compile time, for example. When `std` is not enabled,
this crate will still attempt to use SSE2 accelerated routines on `x86_64`. It
will also use AVX2 accelerated routines when the `avx2` feature is enabled at
compile time. In general, enable this feature if you can.
* **alloc** - When enabled (the default), APIs in this crate requiring some
kind of allocation will become available. For example, the
[`memmem::Finder::into_owned`](crate::memmem::Finder::into_owned) API and the
[`arch::all::shiftor`](crate::arch::all::shiftor) substring search
implementation. Otherwise, this crate is designed from the ground up to be
usable in core-only contexts, so the `alloc` feature doesn't add much
currently. Notably, disabling `std` but enabling `alloc` will **not** result
in the use of AVX2 on `x86_64` targets unless the `avx2` feature is enabled
at compile time. (With `std` enabled, AVX2 can be used even without the `avx2`
feature enabled at compile time by way of runtime CPU feature detection.)
* **logging** - When enabled (disabled by default), the `log` crate is used
to emit log messages about what kinds of `memchr` and `memmem` algorithms
are used. Namely, both `memchr` and `memmem` have a number of different
implementation choices depending on the target and CPU, and the log messages
can help show what specific implementations are being used. Generally, this is
useful for debugging performance issues.
* **libc** - **DEPRECATED**. Previously, this enabled the use of the target's
`memchr` function from whatever `libc` was linked into the program. This
feature is now a no-op because this crate's implementation of `memchr` should
now be sufficiently fast on a number of platforms that `libc` should no longer
be needed. (This feature is somewhat of a holdover from this crate's origins.
Originally, this crate was literally just a safe wrapper function around the
`memchr` function from `libc`.)
*/
#![deny(missing_docs)]
#![no_std]
// It's just not worth trying to squash all dead code warnings. Pretty
// unfortunate IMO. Not really sure how to fix this other than to either
// live with it or sprinkle a whole mess of `cfg` annotations everywhere.
#![cfg_attr(
not(any(
all(target_arch = "x86_64", target_feature = "sse2"),
target_arch = "wasm32",
target_arch = "aarch64",
)),
allow(dead_code)
)]
// Same deal for miri.
#![cfg_attr(miri, allow(dead_code, unused_macros))]
// Supporting 8-bit (or others) would be fine. If you need it, please submit a
// bug report at https://github.com/BurntSushi/memchr
#[cfg(not(any(
target_pointer_width = "16",
target_pointer_width = "32",
target_pointer_width = "64"
)))]
compile_error!("memchr currently not supported on non-{16,32,64}");
#[cfg(any(test, feature = "std"))]
extern crate std;
#[cfg(any(test, feature = "alloc"))]
extern crate alloc;
pub use crate::memchr::{
memchr, memchr2, memchr2_iter, memchr3, memchr3_iter, memchr_iter,
memrchr, memrchr2, memrchr2_iter, memrchr3, memrchr3_iter, memrchr_iter,
Memchr, Memchr2, Memchr3,
};
#[macro_use]
mod macros;
#[cfg(test)]
#[macro_use]
mod tests;
pub mod arch;
mod cow;
mod ext;
mod memchr;
pub mod memmem;
mod vector;

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// Some feature combinations result in some of these macros never being used.
// Which is fine. Just squash the warnings.
#![allow(unused_macros)]
macro_rules! log {
($($tt:tt)*) => {
#[cfg(feature = "logging")]
{
$($tt)*
}
}
}
macro_rules! debug {
($($tt:tt)*) => { log!(log::debug!($($tt)*)) }
}
macro_rules! trace {
($($tt:tt)*) => { log!(log::trace!($($tt)*)) }
}

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use core::iter::Rev;
use crate::arch::generic::memchr as generic;
/// Search for the first occurrence of a byte in a slice.
///
/// This returns the index corresponding to the first occurrence of `needle` in
/// `haystack`, or `None` if one is not found. If an index is returned, it is
/// guaranteed to be less than `haystack.len()`.
///
/// While this is semantically the same as something like
/// `haystack.iter().position(|&b| b == needle)`, this routine will attempt to
/// use highly optimized vector operations that can be an order of magnitude
/// faster (or more).
///
/// # Example
///
/// This shows how to find the first position of a byte in a byte string.
///
/// ```
/// use memchr::memchr;
///
/// let haystack = b"the quick brown fox";
/// assert_eq!(memchr(b'k', haystack), Some(8));
/// ```
#[inline]
pub fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
// SAFETY: memchr_raw, when a match is found, always returns a valid
// pointer between start and end.
unsafe {
generic::search_slice_with_raw(haystack, |start, end| {
memchr_raw(needle, start, end)
})
}
}
/// Search for the last occurrence of a byte in a slice.
///
/// This returns the index corresponding to the last occurrence of `needle` in
/// `haystack`, or `None` if one is not found. If an index is returned, it is
/// guaranteed to be less than `haystack.len()`.
///
/// While this is semantically the same as something like
/// `haystack.iter().rposition(|&b| b == needle)`, this routine will attempt to
/// use highly optimized vector operations that can be an order of magnitude
/// faster (or more).
///
/// # Example
///
/// This shows how to find the last position of a byte in a byte string.
///
/// ```
/// use memchr::memrchr;
///
/// let haystack = b"the quick brown fox";
/// assert_eq!(memrchr(b'o', haystack), Some(17));
/// ```
#[inline]
pub fn memrchr(needle: u8, haystack: &[u8]) -> Option<usize> {
// SAFETY: memrchr_raw, when a match is found, always returns a valid
// pointer between start and end.
unsafe {
generic::search_slice_with_raw(haystack, |start, end| {
memrchr_raw(needle, start, end)
})
}
}
/// Search for the first occurrence of two possible bytes in a haystack.
///
/// This returns the index corresponding to the first occurrence of one of the
/// needle bytes in `haystack`, or `None` if one is not found. If an index is
/// returned, it is guaranteed to be less than `haystack.len()`.
///
/// While this is semantically the same as something like
/// `haystack.iter().position(|&b| b == needle1 || b == needle2)`, this routine
/// will attempt to use highly optimized vector operations that can be an order
/// of magnitude faster (or more).
///
/// # Example
///
/// This shows how to find the first position of one of two possible bytes in a
/// haystack.
///
/// ```
/// use memchr::memchr2;
///
/// let haystack = b"the quick brown fox";
/// assert_eq!(memchr2(b'k', b'q', haystack), Some(4));
/// ```
#[inline]
pub fn memchr2(needle1: u8, needle2: u8, haystack: &[u8]) -> Option<usize> {
// SAFETY: memchr2_raw, when a match is found, always returns a valid
// pointer between start and end.
unsafe {
generic::search_slice_with_raw(haystack, |start, end| {
memchr2_raw(needle1, needle2, start, end)
})
}
}
/// Search for the last occurrence of two possible bytes in a haystack.
///
/// This returns the index corresponding to the last occurrence of one of the
/// needle bytes in `haystack`, or `None` if one is not found. If an index is
/// returned, it is guaranteed to be less than `haystack.len()`.
///
/// While this is semantically the same as something like
/// `haystack.iter().rposition(|&b| b == needle1 || b == needle2)`, this
/// routine will attempt to use highly optimized vector operations that can be
/// an order of magnitude faster (or more).
///
/// # Example
///
/// This shows how to find the last position of one of two possible bytes in a
/// haystack.
///
/// ```
/// use memchr::memrchr2;
///
/// let haystack = b"the quick brown fox";
/// assert_eq!(memrchr2(b'k', b'o', haystack), Some(17));
/// ```
#[inline]
pub fn memrchr2(needle1: u8, needle2: u8, haystack: &[u8]) -> Option<usize> {
// SAFETY: memrchr2_raw, when a match is found, always returns a valid
// pointer between start and end.
unsafe {
generic::search_slice_with_raw(haystack, |start, end| {
memrchr2_raw(needle1, needle2, start, end)
})
}
}
/// Search for the first occurrence of three possible bytes in a haystack.
///
/// This returns the index corresponding to the first occurrence of one of the
/// needle bytes in `haystack`, or `None` if one is not found. If an index is
/// returned, it is guaranteed to be less than `haystack.len()`.
///
/// While this is semantically the same as something like
/// `haystack.iter().position(|&b| b == needle1 || b == needle2 || b == needle3)`,
/// this routine will attempt to use highly optimized vector operations that
/// can be an order of magnitude faster (or more).
///
/// # Example
///
/// This shows how to find the first position of one of three possible bytes in
/// a haystack.
///
/// ```
/// use memchr::memchr3;
///
/// let haystack = b"the quick brown fox";
/// assert_eq!(memchr3(b'k', b'q', b'u', haystack), Some(4));
/// ```
#[inline]
pub fn memchr3(
needle1: u8,
needle2: u8,
needle3: u8,
haystack: &[u8],
) -> Option<usize> {
// SAFETY: memchr3_raw, when a match is found, always returns a valid
// pointer between start and end.
unsafe {
generic::search_slice_with_raw(haystack, |start, end| {
memchr3_raw(needle1, needle2, needle3, start, end)
})
}
}
/// Search for the last occurrence of three possible bytes in a haystack.
///
/// This returns the index corresponding to the last occurrence of one of the
/// needle bytes in `haystack`, or `None` if one is not found. If an index is
/// returned, it is guaranteed to be less than `haystack.len()`.
///
/// While this is semantically the same as something like
/// `haystack.iter().rposition(|&b| b == needle1 || b == needle2 || b == needle3)`,
/// this routine will attempt to use highly optimized vector operations that
/// can be an order of magnitude faster (or more).
///
/// # Example
///
/// This shows how to find the last position of one of three possible bytes in
/// a haystack.
///
/// ```
/// use memchr::memrchr3;
///
/// let haystack = b"the quick brown fox";
/// assert_eq!(memrchr3(b'k', b'o', b'n', haystack), Some(17));
/// ```
#[inline]
pub fn memrchr3(
needle1: u8,
needle2: u8,
needle3: u8,
haystack: &[u8],
) -> Option<usize> {
// SAFETY: memrchr3_raw, when a match is found, always returns a valid
// pointer between start and end.
unsafe {
generic::search_slice_with_raw(haystack, |start, end| {
memrchr3_raw(needle1, needle2, needle3, start, end)
})
}
}
/// Returns an iterator over all occurrences of the needle in a haystack.
///
/// The iterator returned implements `DoubleEndedIterator`. This means it
/// can also be used to find occurrences in reverse order.
#[inline]
pub fn memchr_iter<'h>(needle: u8, haystack: &'h [u8]) -> Memchr<'h> {
Memchr::new(needle, haystack)
}
/// Returns an iterator over all occurrences of the needle in a haystack, in
/// reverse.
#[inline]
pub fn memrchr_iter(needle: u8, haystack: &[u8]) -> Rev<Memchr<'_>> {
Memchr::new(needle, haystack).rev()
}
/// Returns an iterator over all occurrences of the needles in a haystack.
///
/// The iterator returned implements `DoubleEndedIterator`. This means it
/// can also be used to find occurrences in reverse order.
#[inline]
pub fn memchr2_iter<'h>(
needle1: u8,
needle2: u8,
haystack: &'h [u8],
) -> Memchr2<'h> {
Memchr2::new(needle1, needle2, haystack)
}
/// Returns an iterator over all occurrences of the needles in a haystack, in
/// reverse.
#[inline]
pub fn memrchr2_iter(
needle1: u8,
needle2: u8,
haystack: &[u8],
) -> Rev<Memchr2<'_>> {
Memchr2::new(needle1, needle2, haystack).rev()
}
/// Returns an iterator over all occurrences of the needles in a haystack.
///
/// The iterator returned implements `DoubleEndedIterator`. This means it
/// can also be used to find occurrences in reverse order.
#[inline]
pub fn memchr3_iter<'h>(
needle1: u8,
needle2: u8,
needle3: u8,
haystack: &'h [u8],
) -> Memchr3<'h> {
Memchr3::new(needle1, needle2, needle3, haystack)
}
/// Returns an iterator over all occurrences of the needles in a haystack, in
/// reverse.
#[inline]
pub fn memrchr3_iter(
needle1: u8,
needle2: u8,
needle3: u8,
haystack: &[u8],
) -> Rev<Memchr3<'_>> {
Memchr3::new(needle1, needle2, needle3, haystack).rev()
}
/// An iterator over all occurrences of a single byte in a haystack.
///
/// This iterator implements `DoubleEndedIterator`, which means it can also be
/// used to find occurrences in reverse order.
///
/// This iterator is created by the [`memchr_iter`] or `[memrchr_iter`]
/// functions. It can also be created with the [`Memchr::new`] method.
///
/// The lifetime parameter `'h` refers to the lifetime of the haystack being
/// searched.
#[derive(Clone, Debug)]
pub struct Memchr<'h> {
needle1: u8,
it: crate::arch::generic::memchr::Iter<'h>,
}
impl<'h> Memchr<'h> {
/// Returns an iterator over all occurrences of the needle byte in the
/// given haystack.
///
/// The iterator returned implements `DoubleEndedIterator`. This means it
/// can also be used to find occurrences in reverse order.
#[inline]
pub fn new(needle1: u8, haystack: &'h [u8]) -> Memchr<'h> {
Memchr {
needle1,
it: crate::arch::generic::memchr::Iter::new(haystack),
}
}
}
impl<'h> Iterator for Memchr<'h> {
type Item = usize;
#[inline]
fn next(&mut self) -> Option<usize> {
// SAFETY: All of our implementations of memchr ensure that any
// pointers returns will fall within the start and end bounds, and this
// upholds the safety contract of `self.it.next`.
unsafe {
// NOTE: I attempted to define an enum of previously created
// searchers and then switch on those here instead of just
// calling `memchr_raw` (or `One::new(..).find_raw(..)`). But
// that turned out to have a fair bit of extra overhead when
// searching very small haystacks.
self.it.next(|s, e| memchr_raw(self.needle1, s, e))
}
}
#[inline]
fn count(self) -> usize {
self.it.count(|s, e| {
// SAFETY: We rely on our generic iterator to return valid start
// and end pointers.
unsafe { count_raw(self.needle1, s, e) }
})
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.it.size_hint()
}
}
impl<'h> DoubleEndedIterator for Memchr<'h> {
#[inline]
fn next_back(&mut self) -> Option<usize> {
// SAFETY: All of our implementations of memchr ensure that any
// pointers returns will fall within the start and end bounds, and this
// upholds the safety contract of `self.it.next_back`.
unsafe { self.it.next_back(|s, e| memrchr_raw(self.needle1, s, e)) }
}
}
impl<'h> core::iter::FusedIterator for Memchr<'h> {}
/// An iterator over all occurrences of two possible bytes in a haystack.
///
/// This iterator implements `DoubleEndedIterator`, which means it can also be
/// used to find occurrences in reverse order.
///
/// This iterator is created by the [`memchr2_iter`] or `[memrchr2_iter`]
/// functions. It can also be created with the [`Memchr2::new`] method.
///
/// The lifetime parameter `'h` refers to the lifetime of the haystack being
/// searched.
#[derive(Clone, Debug)]
pub struct Memchr2<'h> {
needle1: u8,
needle2: u8,
it: crate::arch::generic::memchr::Iter<'h>,
}
impl<'h> Memchr2<'h> {
/// Returns an iterator over all occurrences of the needle bytes in the
/// given haystack.
///
/// The iterator returned implements `DoubleEndedIterator`. This means it
/// can also be used to find occurrences in reverse order.
#[inline]
pub fn new(needle1: u8, needle2: u8, haystack: &'h [u8]) -> Memchr2<'h> {
Memchr2 {
needle1,
needle2,
it: crate::arch::generic::memchr::Iter::new(haystack),
}
}
}
impl<'h> Iterator for Memchr2<'h> {
type Item = usize;
#[inline]
fn next(&mut self) -> Option<usize> {
// SAFETY: All of our implementations of memchr ensure that any
// pointers returns will fall within the start and end bounds, and this
// upholds the safety contract of `self.it.next`.
unsafe {
self.it.next(|s, e| memchr2_raw(self.needle1, self.needle2, s, e))
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.it.size_hint()
}
}
impl<'h> DoubleEndedIterator for Memchr2<'h> {
#[inline]
fn next_back(&mut self) -> Option<usize> {
// SAFETY: All of our implementations of memchr ensure that any
// pointers returns will fall within the start and end bounds, and this
// upholds the safety contract of `self.it.next_back`.
unsafe {
self.it.next_back(|s, e| {
memrchr2_raw(self.needle1, self.needle2, s, e)
})
}
}
}
impl<'h> core::iter::FusedIterator for Memchr2<'h> {}
/// An iterator over all occurrences of three possible bytes in a haystack.
///
/// This iterator implements `DoubleEndedIterator`, which means it can also be
/// used to find occurrences in reverse order.
///
/// This iterator is created by the [`memchr2_iter`] or `[memrchr2_iter`]
/// functions. It can also be created with the [`Memchr3::new`] method.
///
/// The lifetime parameter `'h` refers to the lifetime of the haystack being
/// searched.
#[derive(Clone, Debug)]
pub struct Memchr3<'h> {
needle1: u8,
needle2: u8,
needle3: u8,
it: crate::arch::generic::memchr::Iter<'h>,
}
impl<'h> Memchr3<'h> {
/// Returns an iterator over all occurrences of the needle bytes in the
/// given haystack.
///
/// The iterator returned implements `DoubleEndedIterator`. This means it
/// can also be used to find occurrences in reverse order.
#[inline]
pub fn new(
needle1: u8,
needle2: u8,
needle3: u8,
haystack: &'h [u8],
) -> Memchr3<'h> {
Memchr3 {
needle1,
needle2,
needle3,
it: crate::arch::generic::memchr::Iter::new(haystack),
}
}
}
impl<'h> Iterator for Memchr3<'h> {
type Item = usize;
#[inline]
fn next(&mut self) -> Option<usize> {
// SAFETY: All of our implementations of memchr ensure that any
// pointers returns will fall within the start and end bounds, and this
// upholds the safety contract of `self.it.next`.
unsafe {
self.it.next(|s, e| {
memchr3_raw(self.needle1, self.needle2, self.needle3, s, e)
})
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.it.size_hint()
}
}
impl<'h> DoubleEndedIterator for Memchr3<'h> {
#[inline]
fn next_back(&mut self) -> Option<usize> {
// SAFETY: All of our implementations of memchr ensure that any
// pointers returns will fall within the start and end bounds, and this
// upholds the safety contract of `self.it.next_back`.
unsafe {
self.it.next_back(|s, e| {
memrchr3_raw(self.needle1, self.needle2, self.needle3, s, e)
})
}
}
}
impl<'h> core::iter::FusedIterator for Memchr3<'h> {}
/// memchr, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::find_raw`.
#[inline]
unsafe fn memchr_raw(
needle: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
#[cfg(target_arch = "x86_64")]
{
// x86_64 does CPU feature detection at runtime in order to use AVX2
// instructions even when the `avx2` feature isn't enabled at compile
// time. This function also handles using a fallback if neither AVX2
// nor SSE2 (unusual) are available.
crate::arch::x86_64::memchr::memchr_raw(needle, start, end)
}
#[cfg(target_arch = "wasm32")]
{
crate::arch::wasm32::memchr::memchr_raw(needle, start, end)
}
#[cfg(target_arch = "aarch64")]
{
crate::arch::aarch64::memchr::memchr_raw(needle, start, end)
}
#[cfg(not(any(
target_arch = "x86_64",
target_arch = "wasm32",
target_arch = "aarch64"
)))]
{
crate::arch::all::memchr::One::new(needle).find_raw(start, end)
}
}
/// memrchr, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::rfind_raw`.
#[inline]
unsafe fn memrchr_raw(
needle: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
#[cfg(target_arch = "x86_64")]
{
crate::arch::x86_64::memchr::memrchr_raw(needle, start, end)
}
#[cfg(target_arch = "wasm32")]
{
crate::arch::wasm32::memchr::memrchr_raw(needle, start, end)
}
#[cfg(target_arch = "aarch64")]
{
crate::arch::aarch64::memchr::memrchr_raw(needle, start, end)
}
#[cfg(not(any(
target_arch = "x86_64",
target_arch = "wasm32",
target_arch = "aarch64"
)))]
{
crate::arch::all::memchr::One::new(needle).rfind_raw(start, end)
}
}
/// memchr2, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Two::find_raw`.
#[inline]
unsafe fn memchr2_raw(
needle1: u8,
needle2: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
#[cfg(target_arch = "x86_64")]
{
crate::arch::x86_64::memchr::memchr2_raw(needle1, needle2, start, end)
}
#[cfg(target_arch = "wasm32")]
{
crate::arch::wasm32::memchr::memchr2_raw(needle1, needle2, start, end)
}
#[cfg(target_arch = "aarch64")]
{
crate::arch::aarch64::memchr::memchr2_raw(needle1, needle2, start, end)
}
#[cfg(not(any(
target_arch = "x86_64",
target_arch = "wasm32",
target_arch = "aarch64"
)))]
{
crate::arch::all::memchr::Two::new(needle1, needle2)
.find_raw(start, end)
}
}
/// memrchr2, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Two::rfind_raw`.
#[inline]
unsafe fn memrchr2_raw(
needle1: u8,
needle2: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
#[cfg(target_arch = "x86_64")]
{
crate::arch::x86_64::memchr::memrchr2_raw(needle1, needle2, start, end)
}
#[cfg(target_arch = "wasm32")]
{
crate::arch::wasm32::memchr::memrchr2_raw(needle1, needle2, start, end)
}
#[cfg(target_arch = "aarch64")]
{
crate::arch::aarch64::memchr::memrchr2_raw(
needle1, needle2, start, end,
)
}
#[cfg(not(any(
target_arch = "x86_64",
target_arch = "wasm32",
target_arch = "aarch64"
)))]
{
crate::arch::all::memchr::Two::new(needle1, needle2)
.rfind_raw(start, end)
}
}
/// memchr3, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Three::find_raw`.
#[inline]
unsafe fn memchr3_raw(
needle1: u8,
needle2: u8,
needle3: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
#[cfg(target_arch = "x86_64")]
{
crate::arch::x86_64::memchr::memchr3_raw(
needle1, needle2, needle3, start, end,
)
}
#[cfg(target_arch = "wasm32")]
{
crate::arch::wasm32::memchr::memchr3_raw(
needle1, needle2, needle3, start, end,
)
}
#[cfg(target_arch = "aarch64")]
{
crate::arch::aarch64::memchr::memchr3_raw(
needle1, needle2, needle3, start, end,
)
}
#[cfg(not(any(
target_arch = "x86_64",
target_arch = "wasm32",
target_arch = "aarch64"
)))]
{
crate::arch::all::memchr::Three::new(needle1, needle2, needle3)
.find_raw(start, end)
}
}
/// memrchr3, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `Three::rfind_raw`.
#[inline]
unsafe fn memrchr3_raw(
needle1: u8,
needle2: u8,
needle3: u8,
start: *const u8,
end: *const u8,
) -> Option<*const u8> {
#[cfg(target_arch = "x86_64")]
{
crate::arch::x86_64::memchr::memrchr3_raw(
needle1, needle2, needle3, start, end,
)
}
#[cfg(target_arch = "wasm32")]
{
crate::arch::wasm32::memchr::memrchr3_raw(
needle1, needle2, needle3, start, end,
)
}
#[cfg(target_arch = "aarch64")]
{
crate::arch::aarch64::memchr::memrchr3_raw(
needle1, needle2, needle3, start, end,
)
}
#[cfg(not(any(
target_arch = "x86_64",
target_arch = "wasm32",
target_arch = "aarch64"
)))]
{
crate::arch::all::memchr::Three::new(needle1, needle2, needle3)
.rfind_raw(start, end)
}
}
/// Count all matching bytes, but using raw pointers to represent the haystack.
///
/// # Safety
///
/// Pointers must be valid. See `One::count_raw`.
#[inline]
unsafe fn count_raw(needle: u8, start: *const u8, end: *const u8) -> usize {
#[cfg(target_arch = "x86_64")]
{
crate::arch::x86_64::memchr::count_raw(needle, start, end)
}
#[cfg(target_arch = "wasm32")]
{
crate::arch::wasm32::memchr::count_raw(needle, start, end)
}
#[cfg(target_arch = "aarch64")]
{
crate::arch::aarch64::memchr::count_raw(needle, start, end)
}
#[cfg(not(any(
target_arch = "x86_64",
target_arch = "wasm32",
target_arch = "aarch64"
)))]
{
crate::arch::all::memchr::One::new(needle).count_raw(start, end)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn forward1_iter() {
crate::tests::memchr::Runner::new(1).forward_iter(
|haystack, needles| {
Some(memchr_iter(needles[0], haystack).collect())
},
)
}
#[test]
fn forward1_oneshot() {
crate::tests::memchr::Runner::new(1).forward_oneshot(
|haystack, needles| Some(memchr(needles[0], haystack)),
)
}
#[test]
fn reverse1_iter() {
crate::tests::memchr::Runner::new(1).reverse_iter(
|haystack, needles| {
Some(memrchr_iter(needles[0], haystack).collect())
},
)
}
#[test]
fn reverse1_oneshot() {
crate::tests::memchr::Runner::new(1).reverse_oneshot(
|haystack, needles| Some(memrchr(needles[0], haystack)),
)
}
#[test]
fn count1_iter() {
crate::tests::memchr::Runner::new(1).count_iter(|haystack, needles| {
Some(memchr_iter(needles[0], haystack).count())
})
}
#[test]
fn forward2_iter() {
crate::tests::memchr::Runner::new(2).forward_iter(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
Some(memchr2_iter(n1, n2, haystack).collect())
},
)
}
#[test]
fn forward2_oneshot() {
crate::tests::memchr::Runner::new(2).forward_oneshot(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
Some(memchr2(n1, n2, haystack))
},
)
}
#[test]
fn reverse2_iter() {
crate::tests::memchr::Runner::new(2).reverse_iter(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
Some(memrchr2_iter(n1, n2, haystack).collect())
},
)
}
#[test]
fn reverse2_oneshot() {
crate::tests::memchr::Runner::new(2).reverse_oneshot(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
Some(memrchr2(n1, n2, haystack))
},
)
}
#[test]
fn forward3_iter() {
crate::tests::memchr::Runner::new(3).forward_iter(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
let n3 = needles.get(2).copied()?;
Some(memchr3_iter(n1, n2, n3, haystack).collect())
},
)
}
#[test]
fn forward3_oneshot() {
crate::tests::memchr::Runner::new(3).forward_oneshot(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
let n3 = needles.get(2).copied()?;
Some(memchr3(n1, n2, n3, haystack))
},
)
}
#[test]
fn reverse3_iter() {
crate::tests::memchr::Runner::new(3).reverse_iter(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
let n3 = needles.get(2).copied()?;
Some(memrchr3_iter(n1, n2, n3, haystack).collect())
},
)
}
#[test]
fn reverse3_oneshot() {
crate::tests::memchr::Runner::new(3).reverse_oneshot(
|haystack, needles| {
let n1 = needles.get(0).copied()?;
let n2 = needles.get(1).copied()?;
let n3 = needles.get(2).copied()?;
Some(memrchr3(n1, n2, n3, haystack))
},
)
}
// Prior to memchr 2.6, the memchr iterators both implemented Send and
// Sync. But in memchr 2.6, the iterator changed to use raw pointers
// internally and I didn't add explicit Send/Sync impls. This ended up
// regressing the API. This test ensures we don't do that again.
//
// See: https://github.com/BurntSushi/memchr/issues/133
#[test]
fn sync_regression() {
use core::panic::{RefUnwindSafe, UnwindSafe};
fn assert_send_sync<T: Send + Sync + UnwindSafe + RefUnwindSafe>() {}
assert_send_sync::<Memchr>();
assert_send_sync::<Memchr2>();
assert_send_sync::<Memchr3>()
}
}

737
vendor/memchr/src/memmem/mod.rs vendored Normal file
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@ -0,0 +1,737 @@
/*!
This module provides forward and reverse substring search routines.
Unlike the standard library's substring search routines, these work on
arbitrary bytes. For all non-empty needles, these routines will report exactly
the same values as the corresponding routines in the standard library. For
the empty needle, the standard library reports matches only at valid UTF-8
boundaries, where as these routines will report matches at every position.
Other than being able to work on arbitrary bytes, the primary reason to prefer
these routines over the standard library routines is that these will generally
be faster. In some cases, significantly so.
# Example: iterating over substring matches
This example shows how to use [`find_iter`] to find occurrences of a substring
in a haystack.
```
use memchr::memmem;
let haystack = b"foo bar foo baz foo";
let mut it = memmem::find_iter(haystack, "foo");
assert_eq!(Some(0), it.next());
assert_eq!(Some(8), it.next());
assert_eq!(Some(16), it.next());
assert_eq!(None, it.next());
```
# Example: iterating over substring matches in reverse
This example shows how to use [`rfind_iter`] to find occurrences of a substring
in a haystack starting from the end of the haystack.
**NOTE:** This module does not implement double ended iterators, so reverse
searches aren't done by calling `rev` on a forward iterator.
```
use memchr::memmem;
let haystack = b"foo bar foo baz foo";
let mut it = memmem::rfind_iter(haystack, "foo");
assert_eq!(Some(16), it.next());
assert_eq!(Some(8), it.next());
assert_eq!(Some(0), it.next());
assert_eq!(None, it.next());
```
# Example: repeating a search for the same needle
It may be possible for the overhead of constructing a substring searcher to be
measurable in some workloads. In cases where the same needle is used to search
many haystacks, it is possible to do construction once and thus to avoid it for
subsequent searches. This can be done with a [`Finder`] (or a [`FinderRev`] for
reverse searches).
```
use memchr::memmem;
let finder = memmem::Finder::new("foo");
assert_eq!(Some(4), finder.find(b"baz foo quux"));
assert_eq!(None, finder.find(b"quux baz bar"));
```
*/
pub use crate::memmem::searcher::PrefilterConfig as Prefilter;
// This is exported here for use in the crate::arch::all::twoway
// implementation. This is essentially an abstraction breaker. Namely, the
// public API of twoway doesn't support providing a prefilter, but its crate
// internal API does. The main reason for this is that I didn't want to do the
// API design required to support it without a concrete use case.
pub(crate) use crate::memmem::searcher::Pre;
use crate::{
arch::all::{
packedpair::{DefaultFrequencyRank, HeuristicFrequencyRank},
rabinkarp,
},
cow::CowBytes,
memmem::searcher::{PrefilterState, Searcher, SearcherRev},
};
mod searcher;
/// Returns an iterator over all non-overlapping occurrences of a substring in
/// a haystack.
///
/// # Complexity
///
/// This routine is guaranteed to have worst case linear time complexity
/// with respect to both the needle and the haystack. That is, this runs
/// in `O(needle.len() + haystack.len())` time.
///
/// This routine is also guaranteed to have worst case constant space
/// complexity.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use memchr::memmem;
///
/// let haystack = b"foo bar foo baz foo";
/// let mut it = memmem::find_iter(haystack, b"foo");
/// assert_eq!(Some(0), it.next());
/// assert_eq!(Some(8), it.next());
/// assert_eq!(Some(16), it.next());
/// assert_eq!(None, it.next());
/// ```
#[inline]
pub fn find_iter<'h, 'n, N: 'n + ?Sized + AsRef<[u8]>>(
haystack: &'h [u8],
needle: &'n N,
) -> FindIter<'h, 'n> {
FindIter::new(haystack, Finder::new(needle))
}
/// Returns a reverse iterator over all non-overlapping occurrences of a
/// substring in a haystack.
///
/// # Complexity
///
/// This routine is guaranteed to have worst case linear time complexity
/// with respect to both the needle and the haystack. That is, this runs
/// in `O(needle.len() + haystack.len())` time.
///
/// This routine is also guaranteed to have worst case constant space
/// complexity.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use memchr::memmem;
///
/// let haystack = b"foo bar foo baz foo";
/// let mut it = memmem::rfind_iter(haystack, b"foo");
/// assert_eq!(Some(16), it.next());
/// assert_eq!(Some(8), it.next());
/// assert_eq!(Some(0), it.next());
/// assert_eq!(None, it.next());
/// ```
#[inline]
pub fn rfind_iter<'h, 'n, N: 'n + ?Sized + AsRef<[u8]>>(
haystack: &'h [u8],
needle: &'n N,
) -> FindRevIter<'h, 'n> {
FindRevIter::new(haystack, FinderRev::new(needle))
}
/// Returns the index of the first occurrence of the given needle.
///
/// Note that if you're are searching for the same needle in many different
/// small haystacks, it may be faster to initialize a [`Finder`] once,
/// and reuse it for each search.
///
/// # Complexity
///
/// This routine is guaranteed to have worst case linear time complexity
/// with respect to both the needle and the haystack. That is, this runs
/// in `O(needle.len() + haystack.len())` time.
///
/// This routine is also guaranteed to have worst case constant space
/// complexity.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use memchr::memmem;
///
/// let haystack = b"foo bar baz";
/// assert_eq!(Some(0), memmem::find(haystack, b"foo"));
/// assert_eq!(Some(4), memmem::find(haystack, b"bar"));
/// assert_eq!(None, memmem::find(haystack, b"quux"));
/// ```
#[inline]
pub fn find(haystack: &[u8], needle: &[u8]) -> Option<usize> {
if haystack.len() < 64 {
rabinkarp::Finder::new(needle).find(haystack, needle)
} else {
Finder::new(needle).find(haystack)
}
}
/// Returns the index of the last occurrence of the given needle.
///
/// Note that if you're are searching for the same needle in many different
/// small haystacks, it may be faster to initialize a [`FinderRev`] once,
/// and reuse it for each search.
///
/// # Complexity
///
/// This routine is guaranteed to have worst case linear time complexity
/// with respect to both the needle and the haystack. That is, this runs
/// in `O(needle.len() + haystack.len())` time.
///
/// This routine is also guaranteed to have worst case constant space
/// complexity.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use memchr::memmem;
///
/// let haystack = b"foo bar baz";
/// assert_eq!(Some(0), memmem::rfind(haystack, b"foo"));
/// assert_eq!(Some(4), memmem::rfind(haystack, b"bar"));
/// assert_eq!(Some(8), memmem::rfind(haystack, b"ba"));
/// assert_eq!(None, memmem::rfind(haystack, b"quux"));
/// ```
#[inline]
pub fn rfind(haystack: &[u8], needle: &[u8]) -> Option<usize> {
if haystack.len() < 64 {
rabinkarp::FinderRev::new(needle).rfind(haystack, needle)
} else {
FinderRev::new(needle).rfind(haystack)
}
}
/// An iterator over non-overlapping substring matches.
///
/// Matches are reported by the byte offset at which they begin.
///
/// `'h` is the lifetime of the haystack while `'n` is the lifetime of the
/// needle.
#[derive(Debug, Clone)]
pub struct FindIter<'h, 'n> {
haystack: &'h [u8],
prestate: PrefilterState,
finder: Finder<'n>,
pos: usize,
}
impl<'h, 'n> FindIter<'h, 'n> {
#[inline(always)]
pub(crate) fn new(
haystack: &'h [u8],
finder: Finder<'n>,
) -> FindIter<'h, 'n> {
let prestate = PrefilterState::new();
FindIter { haystack, prestate, finder, pos: 0 }
}
/// Convert this iterator into its owned variant, such that it no longer
/// borrows the finder and needle.
///
/// If this is already an owned iterator, then this is a no-op. Otherwise,
/// this copies the needle.
///
/// This is only available when the `alloc` feature is enabled.
#[cfg(feature = "alloc")]
#[inline]
pub fn into_owned(self) -> FindIter<'h, 'static> {
FindIter {
haystack: self.haystack,
prestate: self.prestate,
finder: self.finder.into_owned(),
pos: self.pos,
}
}
}
impl<'h, 'n> Iterator for FindIter<'h, 'n> {
type Item = usize;
fn next(&mut self) -> Option<usize> {
let needle = self.finder.needle();
let haystack = self.haystack.get(self.pos..)?;
let idx =
self.finder.searcher.find(&mut self.prestate, haystack, needle)?;
let pos = self.pos + idx;
self.pos = pos + needle.len().max(1);
Some(pos)
}
fn size_hint(&self) -> (usize, Option<usize>) {
// The largest possible number of non-overlapping matches is the
// quotient of the haystack and the needle (or the length of the
// haystack, if the needle is empty)
match self.haystack.len().checked_sub(self.pos) {
None => (0, Some(0)),
Some(haystack_len) => match self.finder.needle().len() {
// Empty needles always succeed and match at every point
// (including the very end)
0 => (
haystack_len.saturating_add(1),
haystack_len.checked_add(1),
),
needle_len => (0, Some(haystack_len / needle_len)),
},
}
}
}
/// An iterator over non-overlapping substring matches in reverse.
///
/// Matches are reported by the byte offset at which they begin.
///
/// `'h` is the lifetime of the haystack while `'n` is the lifetime of the
/// needle.
#[derive(Clone, Debug)]
pub struct FindRevIter<'h, 'n> {
haystack: &'h [u8],
finder: FinderRev<'n>,
/// When searching with an empty needle, this gets set to `None` after
/// we've yielded the last element at `0`.
pos: Option<usize>,
}
impl<'h, 'n> FindRevIter<'h, 'n> {
#[inline(always)]
pub(crate) fn new(
haystack: &'h [u8],
finder: FinderRev<'n>,
) -> FindRevIter<'h, 'n> {
let pos = Some(haystack.len());
FindRevIter { haystack, finder, pos }
}
/// Convert this iterator into its owned variant, such that it no longer
/// borrows the finder and needle.
///
/// If this is already an owned iterator, then this is a no-op. Otherwise,
/// this copies the needle.
///
/// This is only available when the `std` feature is enabled.
#[cfg(feature = "alloc")]
#[inline]
pub fn into_owned(self) -> FindRevIter<'h, 'static> {
FindRevIter {
haystack: self.haystack,
finder: self.finder.into_owned(),
pos: self.pos,
}
}
}
impl<'h, 'n> Iterator for FindRevIter<'h, 'n> {
type Item = usize;
fn next(&mut self) -> Option<usize> {
let pos = match self.pos {
None => return None,
Some(pos) => pos,
};
let result = self.finder.rfind(&self.haystack[..pos]);
match result {
None => None,
Some(i) => {
if pos == i {
self.pos = pos.checked_sub(1);
} else {
self.pos = Some(i);
}
Some(i)
}
}
}
}
/// A single substring searcher fixed to a particular needle.
///
/// The purpose of this type is to permit callers to construct a substring
/// searcher that can be used to search haystacks without the overhead of
/// constructing the searcher in the first place. This is a somewhat niche
/// concern when it's necessary to re-use the same needle to search multiple
/// different haystacks with as little overhead as possible. In general, using
/// [`find`] is good enough, but `Finder` is useful when you can meaningfully
/// observe searcher construction time in a profile.
///
/// When the `std` feature is enabled, then this type has an `into_owned`
/// version which permits building a `Finder` that is not connected to
/// the lifetime of its needle.
#[derive(Clone, Debug)]
pub struct Finder<'n> {
needle: CowBytes<'n>,
searcher: Searcher,
}
impl<'n> Finder<'n> {
/// Create a new finder for the given needle.
#[inline]
pub fn new<B: ?Sized + AsRef<[u8]>>(needle: &'n B) -> Finder<'n> {
FinderBuilder::new().build_forward(needle)
}
/// Returns the index of the first occurrence of this needle in the given
/// haystack.
///
/// # Complexity
///
/// This routine is guaranteed to have worst case linear time complexity
/// with respect to both the needle and the haystack. That is, this runs
/// in `O(needle.len() + haystack.len())` time.
///
/// This routine is also guaranteed to have worst case constant space
/// complexity.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use memchr::memmem::Finder;
///
/// let haystack = b"foo bar baz";
/// assert_eq!(Some(0), Finder::new("foo").find(haystack));
/// assert_eq!(Some(4), Finder::new("bar").find(haystack));
/// assert_eq!(None, Finder::new("quux").find(haystack));
/// ```
#[inline]
pub fn find(&self, haystack: &[u8]) -> Option<usize> {
let mut prestate = PrefilterState::new();
let needle = self.needle.as_slice();
self.searcher.find(&mut prestate, haystack, needle)
}
/// Returns an iterator over all occurrences of a substring in a haystack.
///
/// # Complexity
///
/// This routine is guaranteed to have worst case linear time complexity
/// with respect to both the needle and the haystack. That is, this runs
/// in `O(needle.len() + haystack.len())` time.
///
/// This routine is also guaranteed to have worst case constant space
/// complexity.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use memchr::memmem::Finder;
///
/// let haystack = b"foo bar foo baz foo";
/// let finder = Finder::new(b"foo");
/// let mut it = finder.find_iter(haystack);
/// assert_eq!(Some(0), it.next());
/// assert_eq!(Some(8), it.next());
/// assert_eq!(Some(16), it.next());
/// assert_eq!(None, it.next());
/// ```
#[inline]
pub fn find_iter<'a, 'h>(
&'a self,
haystack: &'h [u8],
) -> FindIter<'h, 'a> {
FindIter::new(haystack, self.as_ref())
}
/// Convert this finder into its owned variant, such that it no longer
/// borrows the needle.
///
/// If this is already an owned finder, then this is a no-op. Otherwise,
/// this copies the needle.
///
/// This is only available when the `alloc` feature is enabled.
#[cfg(feature = "alloc")]
#[inline]
pub fn into_owned(self) -> Finder<'static> {
Finder {
needle: self.needle.into_owned(),
searcher: self.searcher.clone(),
}
}
/// Convert this finder into its borrowed variant.
///
/// This is primarily useful if your finder is owned and you'd like to
/// store its borrowed variant in some intermediate data structure.
///
/// Note that the lifetime parameter of the returned finder is tied to the
/// lifetime of `self`, and may be shorter than the `'n` lifetime of the
/// needle itself. Namely, a finder's needle can be either borrowed or
/// owned, so the lifetime of the needle returned must necessarily be the
/// shorter of the two.
#[inline]
pub fn as_ref(&self) -> Finder<'_> {
Finder {
needle: CowBytes::new(self.needle()),
searcher: self.searcher.clone(),
}
}
/// Returns the needle that this finder searches for.
///
/// Note that the lifetime of the needle returned is tied to the lifetime
/// of the finder, and may be shorter than the `'n` lifetime. Namely, a
/// finder's needle can be either borrowed or owned, so the lifetime of the
/// needle returned must necessarily be the shorter of the two.
#[inline]
pub fn needle(&self) -> &[u8] {
self.needle.as_slice()
}
}
/// A single substring reverse searcher fixed to a particular needle.
///
/// The purpose of this type is to permit callers to construct a substring
/// searcher that can be used to search haystacks without the overhead of
/// constructing the searcher in the first place. This is a somewhat niche
/// concern when it's necessary to re-use the same needle to search multiple
/// different haystacks with as little overhead as possible. In general,
/// using [`rfind`] is good enough, but `FinderRev` is useful when you can
/// meaningfully observe searcher construction time in a profile.
///
/// When the `std` feature is enabled, then this type has an `into_owned`
/// version which permits building a `FinderRev` that is not connected to
/// the lifetime of its needle.
#[derive(Clone, Debug)]
pub struct FinderRev<'n> {
needle: CowBytes<'n>,
searcher: SearcherRev,
}
impl<'n> FinderRev<'n> {
/// Create a new reverse finder for the given needle.
#[inline]
pub fn new<B: ?Sized + AsRef<[u8]>>(needle: &'n B) -> FinderRev<'n> {
FinderBuilder::new().build_reverse(needle)
}
/// Returns the index of the last occurrence of this needle in the given
/// haystack.
///
/// The haystack may be any type that can be cheaply converted into a
/// `&[u8]`. This includes, but is not limited to, `&str` and `&[u8]`.
///
/// # Complexity
///
/// This routine is guaranteed to have worst case linear time complexity
/// with respect to both the needle and the haystack. That is, this runs
/// in `O(needle.len() + haystack.len())` time.
///
/// This routine is also guaranteed to have worst case constant space
/// complexity.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use memchr::memmem::FinderRev;
///
/// let haystack = b"foo bar baz";
/// assert_eq!(Some(0), FinderRev::new("foo").rfind(haystack));
/// assert_eq!(Some(4), FinderRev::new("bar").rfind(haystack));
/// assert_eq!(None, FinderRev::new("quux").rfind(haystack));
/// ```
pub fn rfind<B: AsRef<[u8]>>(&self, haystack: B) -> Option<usize> {
self.searcher.rfind(haystack.as_ref(), self.needle.as_slice())
}
/// Returns a reverse iterator over all occurrences of a substring in a
/// haystack.
///
/// # Complexity
///
/// This routine is guaranteed to have worst case linear time complexity
/// with respect to both the needle and the haystack. That is, this runs
/// in `O(needle.len() + haystack.len())` time.
///
/// This routine is also guaranteed to have worst case constant space
/// complexity.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use memchr::memmem::FinderRev;
///
/// let haystack = b"foo bar foo baz foo";
/// let finder = FinderRev::new(b"foo");
/// let mut it = finder.rfind_iter(haystack);
/// assert_eq!(Some(16), it.next());
/// assert_eq!(Some(8), it.next());
/// assert_eq!(Some(0), it.next());
/// assert_eq!(None, it.next());
/// ```
#[inline]
pub fn rfind_iter<'a, 'h>(
&'a self,
haystack: &'h [u8],
) -> FindRevIter<'h, 'a> {
FindRevIter::new(haystack, self.as_ref())
}
/// Convert this finder into its owned variant, such that it no longer
/// borrows the needle.
///
/// If this is already an owned finder, then this is a no-op. Otherwise,
/// this copies the needle.
///
/// This is only available when the `std` feature is enabled.
#[cfg(feature = "alloc")]
#[inline]
pub fn into_owned(self) -> FinderRev<'static> {
FinderRev {
needle: self.needle.into_owned(),
searcher: self.searcher.clone(),
}
}
/// Convert this finder into its borrowed variant.
///
/// This is primarily useful if your finder is owned and you'd like to
/// store its borrowed variant in some intermediate data structure.
///
/// Note that the lifetime parameter of the returned finder is tied to the
/// lifetime of `self`, and may be shorter than the `'n` lifetime of the
/// needle itself. Namely, a finder's needle can be either borrowed or
/// owned, so the lifetime of the needle returned must necessarily be the
/// shorter of the two.
#[inline]
pub fn as_ref(&self) -> FinderRev<'_> {
FinderRev {
needle: CowBytes::new(self.needle()),
searcher: self.searcher.clone(),
}
}
/// Returns the needle that this finder searches for.
///
/// Note that the lifetime of the needle returned is tied to the lifetime
/// of the finder, and may be shorter than the `'n` lifetime. Namely, a
/// finder's needle can be either borrowed or owned, so the lifetime of the
/// needle returned must necessarily be the shorter of the two.
#[inline]
pub fn needle(&self) -> &[u8] {
self.needle.as_slice()
}
}
/// A builder for constructing non-default forward or reverse memmem finders.
///
/// A builder is primarily useful for configuring a substring searcher.
/// Currently, the only configuration exposed is the ability to disable
/// heuristic prefilters used to speed up certain searches.
#[derive(Clone, Debug, Default)]
pub struct FinderBuilder {
prefilter: Prefilter,
}
impl FinderBuilder {
/// Create a new finder builder with default settings.
pub fn new() -> FinderBuilder {
FinderBuilder::default()
}
/// Build a forward finder using the given needle from the current
/// settings.
pub fn build_forward<'n, B: ?Sized + AsRef<[u8]>>(
&self,
needle: &'n B,
) -> Finder<'n> {
self.build_forward_with_ranker(DefaultFrequencyRank, needle)
}
/// Build a forward finder using the given needle and a custom heuristic for
/// determining the frequency of a given byte in the dataset.
/// See [`HeuristicFrequencyRank`] for more details.
pub fn build_forward_with_ranker<
'n,
R: HeuristicFrequencyRank,
B: ?Sized + AsRef<[u8]>,
>(
&self,
ranker: R,
needle: &'n B,
) -> Finder<'n> {
let needle = needle.as_ref();
Finder {
needle: CowBytes::new(needle),
searcher: Searcher::new(self.prefilter, ranker, needle),
}
}
/// Build a reverse finder using the given needle from the current
/// settings.
pub fn build_reverse<'n, B: ?Sized + AsRef<[u8]>>(
&self,
needle: &'n B,
) -> FinderRev<'n> {
let needle = needle.as_ref();
FinderRev {
needle: CowBytes::new(needle),
searcher: SearcherRev::new(needle),
}
}
/// Configure the prefilter setting for the finder.
///
/// See the documentation for [`Prefilter`] for more discussion on why
/// you might want to configure this.
pub fn prefilter(&mut self, prefilter: Prefilter) -> &mut FinderBuilder {
self.prefilter = prefilter;
self
}
}
#[cfg(test)]
mod tests {
use super::*;
define_substring_forward_quickcheck!(|h, n| Some(Finder::new(n).find(h)));
define_substring_reverse_quickcheck!(|h, n| Some(
FinderRev::new(n).rfind(h)
));
#[test]
fn forward() {
crate::tests::substring::Runner::new()
.fwd(|h, n| Some(Finder::new(n).find(h)))
.run();
}
#[test]
fn reverse() {
crate::tests::substring::Runner::new()
.rev(|h, n| Some(FinderRev::new(n).rfind(h)))
.run();
}
}

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use alloc::{
string::{String, ToString},
vec,
vec::Vec,
};
use crate::ext::Byte;
pub(crate) mod naive;
#[macro_use]
pub(crate) mod prop;
const SEEDS: &'static [Seed] = &[
Seed { haystack: "a", needles: &[b'a'], positions: &[0] },
Seed { haystack: "aa", needles: &[b'a'], positions: &[0, 1] },
Seed { haystack: "aaa", needles: &[b'a'], positions: &[0, 1, 2] },
Seed { haystack: "", needles: &[b'a'], positions: &[] },
Seed { haystack: "z", needles: &[b'a'], positions: &[] },
Seed { haystack: "zz", needles: &[b'a'], positions: &[] },
Seed { haystack: "zza", needles: &[b'a'], positions: &[2] },
Seed { haystack: "zaza", needles: &[b'a'], positions: &[1, 3] },
Seed { haystack: "zzza", needles: &[b'a'], positions: &[3] },
Seed { haystack: "\x00a", needles: &[b'a'], positions: &[1] },
Seed { haystack: "\x00", needles: &[b'\x00'], positions: &[0] },
Seed { haystack: "\x00\x00", needles: &[b'\x00'], positions: &[0, 1] },
Seed { haystack: "\x00a\x00", needles: &[b'\x00'], positions: &[0, 2] },
Seed { haystack: "zzzzzzzzzzzzzzzza", needles: &[b'a'], positions: &[16] },
Seed {
haystack: "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzza",
needles: &[b'a'],
positions: &[32],
},
// two needles (applied to memchr2 + memchr3)
Seed { haystack: "az", needles: &[b'a', b'z'], positions: &[0, 1] },
Seed { haystack: "az", needles: &[b'a', b'z'], positions: &[0, 1] },
Seed { haystack: "az", needles: &[b'x', b'y'], positions: &[] },
Seed { haystack: "az", needles: &[b'a', b'y'], positions: &[0] },
Seed { haystack: "az", needles: &[b'x', b'z'], positions: &[1] },
Seed { haystack: "yyyyaz", needles: &[b'a', b'z'], positions: &[4, 5] },
Seed { haystack: "yyyyaz", needles: &[b'z', b'a'], positions: &[4, 5] },
// three needles (applied to memchr3)
Seed {
haystack: "xyz",
needles: &[b'x', b'y', b'z'],
positions: &[0, 1, 2],
},
Seed {
haystack: "zxy",
needles: &[b'x', b'y', b'z'],
positions: &[0, 1, 2],
},
Seed { haystack: "zxy", needles: &[b'x', b'a', b'z'], positions: &[0, 1] },
Seed { haystack: "zxy", needles: &[b't', b'a', b'z'], positions: &[0] },
Seed { haystack: "yxz", needles: &[b't', b'a', b'z'], positions: &[2] },
];
/// Runs a host of substring search tests.
///
/// This has support for "partial" substring search implementations only work
/// for a subset of needles/haystacks. For example, the "packed pair" substring
/// search implementation only works for haystacks of some minimum length based
/// of the pair of bytes selected and the size of the vector used.
pub(crate) struct Runner {
needle_len: usize,
}
impl Runner {
/// Create a new test runner for forward and reverse byte search
/// implementations.
///
/// The `needle_len` given must be at most `3` and at least `1`. It
/// corresponds to the number of needle bytes to search for.
pub(crate) fn new(needle_len: usize) -> Runner {
assert!(needle_len >= 1, "needle_len must be at least 1");
assert!(needle_len <= 3, "needle_len must be at most 3");
Runner { needle_len }
}
/// Run all tests. This panics on the first failure.
///
/// If the implementation being tested returns `None` for a particular
/// haystack/needle combination, then that test is skipped.
pub(crate) fn forward_iter<F>(self, mut test: F)
where
F: FnMut(&[u8], &[u8]) -> Option<Vec<usize>> + 'static,
{
for seed in SEEDS.iter() {
if seed.needles.len() > self.needle_len {
continue;
}
for t in seed.generate() {
let results = match test(t.haystack.as_bytes(), &t.needles) {
None => continue,
Some(results) => results,
};
assert_eq!(
t.expected,
results,
"needles: {:?}, haystack: {:?}",
t.needles
.iter()
.map(|&b| b.to_char())
.collect::<Vec<char>>(),
t.haystack,
);
}
}
}
/// Run all tests in the reverse direction. This panics on the first
/// failure.
///
/// If the implementation being tested returns `None` for a particular
/// haystack/needle combination, then that test is skipped.
pub(crate) fn reverse_iter<F>(self, mut test: F)
where
F: FnMut(&[u8], &[u8]) -> Option<Vec<usize>> + 'static,
{
for seed in SEEDS.iter() {
if seed.needles.len() > self.needle_len {
continue;
}
for t in seed.generate() {
let mut results = match test(t.haystack.as_bytes(), &t.needles)
{
None => continue,
Some(results) => results,
};
results.reverse();
assert_eq!(
t.expected,
results,
"needles: {:?}, haystack: {:?}",
t.needles
.iter()
.map(|&b| b.to_char())
.collect::<Vec<char>>(),
t.haystack,
);
}
}
}
/// Run all tests as counting tests. This panics on the first failure.
///
/// That is, this only checks that the number of matches is correct and
/// not whether the offsets of each match are.
pub(crate) fn count_iter<F>(self, mut test: F)
where
F: FnMut(&[u8], &[u8]) -> Option<usize> + 'static,
{
for seed in SEEDS.iter() {
if seed.needles.len() > self.needle_len {
continue;
}
for t in seed.generate() {
let got = match test(t.haystack.as_bytes(), &t.needles) {
None => continue,
Some(got) => got,
};
assert_eq!(
t.expected.len(),
got,
"needles: {:?}, haystack: {:?}",
t.needles
.iter()
.map(|&b| b.to_char())
.collect::<Vec<char>>(),
t.haystack,
);
}
}
}
/// Like `Runner::forward`, but for a function that returns only the next
/// match and not all matches.
///
/// If the function returns `None`, then it is skipped.
pub(crate) fn forward_oneshot<F>(self, mut test: F)
where
F: FnMut(&[u8], &[u8]) -> Option<Option<usize>> + 'static,
{
self.forward_iter(move |haystack, needles| {
let mut start = 0;
let mut results = vec![];
while let Some(i) = test(&haystack[start..], needles)? {
results.push(start + i);
start += i + 1;
}
Some(results)
})
}
/// Like `Runner::reverse`, but for a function that returns only the last
/// match and not all matches.
///
/// If the function returns `None`, then it is skipped.
pub(crate) fn reverse_oneshot<F>(self, mut test: F)
where
F: FnMut(&[u8], &[u8]) -> Option<Option<usize>> + 'static,
{
self.reverse_iter(move |haystack, needles| {
let mut end = haystack.len();
let mut results = vec![];
while let Some(i) = test(&haystack[..end], needles)? {
results.push(i);
end = i;
}
Some(results)
})
}
}
/// A single test for memr?chr{,2,3}.
#[derive(Clone, Debug)]
struct Test {
/// The string to search in.
haystack: String,
/// The needles to look for.
needles: Vec<u8>,
/// The offsets that are expected to be found for all needles in the
/// forward direction.
expected: Vec<usize>,
}
impl Test {
fn new(seed: &Seed) -> Test {
Test {
haystack: seed.haystack.to_string(),
needles: seed.needles.to_vec(),
expected: seed.positions.to_vec(),
}
}
}
/// Data that can be expanded into many memchr tests by padding out the corpus.
#[derive(Clone, Debug)]
struct Seed {
/// The thing to search. We use `&str` instead of `&[u8]` because they
/// are nicer to write in tests, and we don't miss much since memchr
/// doesn't care about UTF-8.
///
/// Corpora cannot contain either '%' or '#'. We use these bytes when
/// expanding test cases into many test cases, and we assume they are not
/// used. If they are used, `memchr_tests` will panic.
haystack: &'static str,
/// The needles to search for. This is intended to be an alternation of
/// needles. The number of needles may cause this test to be skipped for
/// some memchr variants. For example, a test with 2 needles cannot be used
/// to test `memchr`, but can be used to test `memchr2` and `memchr3`.
/// However, a test with only 1 needle can be used to test all of `memchr`,
/// `memchr2` and `memchr3`. We achieve this by filling in the needles with
/// bytes that we never used in the corpus (such as '#').
needles: &'static [u8],
/// The positions expected to match for all of the needles.
positions: &'static [usize],
}
impl Seed {
/// Controls how much we expand the haystack on either side for each test.
/// We lower this on Miri because otherwise running the tests would take
/// forever.
const EXPAND_LEN: usize = {
#[cfg(not(miri))]
{
515
}
#[cfg(miri)]
{
6
}
};
/// Expand this test into many variations of the same test.
///
/// In particular, this will generate more tests with larger corpus sizes.
/// The expected positions are updated to maintain the integrity of the
/// test.
///
/// This is important in testing a memchr implementation, because there are
/// often different cases depending on the length of the corpus.
///
/// Note that we extend the corpus by adding `%` bytes, which we
/// don't otherwise use as a needle.
fn generate(&self) -> impl Iterator<Item = Test> {
let mut more = vec![];
// Add bytes to the start of the corpus.
for i in 0..Seed::EXPAND_LEN {
let mut t = Test::new(self);
let mut new: String = core::iter::repeat('%').take(i).collect();
new.push_str(&t.haystack);
t.haystack = new;
t.expected = t.expected.into_iter().map(|p| p + i).collect();
more.push(t);
}
// Add bytes to the end of the corpus.
for i in 1..Seed::EXPAND_LEN {
let mut t = Test::new(self);
let padding: String = core::iter::repeat('%').take(i).collect();
t.haystack.push_str(&padding);
more.push(t);
}
more.into_iter()
}
}

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pub(crate) fn memchr(n1: u8, haystack: &[u8]) -> Option<usize> {
haystack.iter().position(|&b| b == n1)
}
pub(crate) fn memchr2(n1: u8, n2: u8, haystack: &[u8]) -> Option<usize> {
haystack.iter().position(|&b| b == n1 || b == n2)
}
pub(crate) fn memchr3(
n1: u8,
n2: u8,
n3: u8,
haystack: &[u8],
) -> Option<usize> {
haystack.iter().position(|&b| b == n1 || b == n2 || b == n3)
}
pub(crate) fn memrchr(n1: u8, haystack: &[u8]) -> Option<usize> {
haystack.iter().rposition(|&b| b == n1)
}
pub(crate) fn memrchr2(n1: u8, n2: u8, haystack: &[u8]) -> Option<usize> {
haystack.iter().rposition(|&b| b == n1 || b == n2)
}
pub(crate) fn memrchr3(
n1: u8,
n2: u8,
n3: u8,
haystack: &[u8],
) -> Option<usize> {
haystack.iter().rposition(|&b| b == n1 || b == n2 || b == n3)
}

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#[cfg(miri)]
#[macro_export]
macro_rules! define_memchr_quickcheck {
($($tt:tt)*) => {};
}
#[cfg(not(miri))]
#[macro_export]
macro_rules! define_memchr_quickcheck {
($mod:ident) => {
define_memchr_quickcheck!($mod, new);
};
($mod:ident, $cons:ident) => {
use alloc::vec::Vec;
use quickcheck::TestResult;
use crate::tests::memchr::{
naive,
prop::{double_ended_take, naive1_iter, naive2_iter, naive3_iter},
};
quickcheck::quickcheck! {
fn qc_memchr_matches_naive(n1: u8, corpus: Vec<u8>) -> TestResult {
let expected = naive::memchr(n1, &corpus);
let got = match $mod::One::$cons(n1) {
None => return TestResult::discard(),
Some(f) => f.find(&corpus),
};
TestResult::from_bool(expected == got)
}
fn qc_memrchr_matches_naive(n1: u8, corpus: Vec<u8>) -> TestResult {
let expected = naive::memrchr(n1, &corpus);
let got = match $mod::One::$cons(n1) {
None => return TestResult::discard(),
Some(f) => f.rfind(&corpus),
};
TestResult::from_bool(expected == got)
}
fn qc_memchr2_matches_naive(n1: u8, n2: u8, corpus: Vec<u8>) -> TestResult {
let expected = naive::memchr2(n1, n2, &corpus);
let got = match $mod::Two::$cons(n1, n2) {
None => return TestResult::discard(),
Some(f) => f.find(&corpus),
};
TestResult::from_bool(expected == got)
}
fn qc_memrchr2_matches_naive(n1: u8, n2: u8, corpus: Vec<u8>) -> TestResult {
let expected = naive::memrchr2(n1, n2, &corpus);
let got = match $mod::Two::$cons(n1, n2) {
None => return TestResult::discard(),
Some(f) => f.rfind(&corpus),
};
TestResult::from_bool(expected == got)
}
fn qc_memchr3_matches_naive(
n1: u8, n2: u8, n3: u8,
corpus: Vec<u8>
) -> TestResult {
let expected = naive::memchr3(n1, n2, n3, &corpus);
let got = match $mod::Three::$cons(n1, n2, n3) {
None => return TestResult::discard(),
Some(f) => f.find(&corpus),
};
TestResult::from_bool(expected == got)
}
fn qc_memrchr3_matches_naive(
n1: u8, n2: u8, n3: u8,
corpus: Vec<u8>
) -> TestResult {
let expected = naive::memrchr3(n1, n2, n3, &corpus);
let got = match $mod::Three::$cons(n1, n2, n3) {
None => return TestResult::discard(),
Some(f) => f.rfind(&corpus),
};
TestResult::from_bool(expected == got)
}
fn qc_memchr_double_ended_iter(
needle: u8, data: Vec<u8>, take_side: Vec<bool>
) -> TestResult {
// make nonempty
let mut take_side = take_side;
if take_side.is_empty() { take_side.push(true) };
let finder = match $mod::One::$cons(needle) {
None => return TestResult::discard(),
Some(finder) => finder,
};
let iter = finder.iter(&data);
let got = double_ended_take(
iter,
take_side.iter().cycle().cloned(),
);
let expected = naive1_iter(needle, &data);
TestResult::from_bool(got.iter().cloned().eq(expected))
}
fn qc_memchr2_double_ended_iter(
needle1: u8, needle2: u8, data: Vec<u8>, take_side: Vec<bool>
) -> TestResult {
// make nonempty
let mut take_side = take_side;
if take_side.is_empty() { take_side.push(true) };
let finder = match $mod::Two::$cons(needle1, needle2) {
None => return TestResult::discard(),
Some(finder) => finder,
};
let iter = finder.iter(&data);
let got = double_ended_take(
iter,
take_side.iter().cycle().cloned(),
);
let expected = naive2_iter(needle1, needle2, &data);
TestResult::from_bool(got.iter().cloned().eq(expected))
}
fn qc_memchr3_double_ended_iter(
needle1: u8, needle2: u8, needle3: u8,
data: Vec<u8>, take_side: Vec<bool>
) -> TestResult {
// make nonempty
let mut take_side = take_side;
if take_side.is_empty() { take_side.push(true) };
let finder = match $mod::Three::$cons(needle1, needle2, needle3) {
None => return TestResult::discard(),
Some(finder) => finder,
};
let iter = finder.iter(&data);
let got = double_ended_take(
iter,
take_side.iter().cycle().cloned(),
);
let expected = naive3_iter(needle1, needle2, needle3, &data);
TestResult::from_bool(got.iter().cloned().eq(expected))
}
fn qc_memchr1_iter(data: Vec<u8>) -> TestResult {
let needle = 0;
let finder = match $mod::One::$cons(needle) {
None => return TestResult::discard(),
Some(finder) => finder,
};
let got = finder.iter(&data);
let expected = naive1_iter(needle, &data);
TestResult::from_bool(got.eq(expected))
}
fn qc_memchr1_rev_iter(data: Vec<u8>) -> TestResult {
let needle = 0;
let finder = match $mod::One::$cons(needle) {
None => return TestResult::discard(),
Some(finder) => finder,
};
let got = finder.iter(&data).rev();
let expected = naive1_iter(needle, &data).rev();
TestResult::from_bool(got.eq(expected))
}
fn qc_memchr2_iter(data: Vec<u8>) -> TestResult {
let needle1 = 0;
let needle2 = 1;
let finder = match $mod::Two::$cons(needle1, needle2) {
None => return TestResult::discard(),
Some(finder) => finder,
};
let got = finder.iter(&data);
let expected = naive2_iter(needle1, needle2, &data);
TestResult::from_bool(got.eq(expected))
}
fn qc_memchr2_rev_iter(data: Vec<u8>) -> TestResult {
let needle1 = 0;
let needle2 = 1;
let finder = match $mod::Two::$cons(needle1, needle2) {
None => return TestResult::discard(),
Some(finder) => finder,
};
let got = finder.iter(&data).rev();
let expected = naive2_iter(needle1, needle2, &data).rev();
TestResult::from_bool(got.eq(expected))
}
fn qc_memchr3_iter(data: Vec<u8>) -> TestResult {
let needle1 = 0;
let needle2 = 1;
let needle3 = 2;
let finder = match $mod::Three::$cons(needle1, needle2, needle3) {
None => return TestResult::discard(),
Some(finder) => finder,
};
let got = finder.iter(&data);
let expected = naive3_iter(needle1, needle2, needle3, &data);
TestResult::from_bool(got.eq(expected))
}
fn qc_memchr3_rev_iter(data: Vec<u8>) -> TestResult {
let needle1 = 0;
let needle2 = 1;
let needle3 = 2;
let finder = match $mod::Three::$cons(needle1, needle2, needle3) {
None => return TestResult::discard(),
Some(finder) => finder,
};
let got = finder.iter(&data).rev();
let expected = naive3_iter(needle1, needle2, needle3, &data).rev();
TestResult::from_bool(got.eq(expected))
}
fn qc_memchr1_iter_size_hint(data: Vec<u8>) -> TestResult {
// test that the size hint is within reasonable bounds
let needle = 0;
let finder = match $mod::One::$cons(needle) {
None => return TestResult::discard(),
Some(finder) => finder,
};
let mut iter = finder.iter(&data);
let mut real_count = data
.iter()
.filter(|&&elt| elt == needle)
.count();
while let Some(index) = iter.next() {
real_count -= 1;
let (lower, upper) = iter.size_hint();
assert!(lower <= real_count);
assert!(upper.unwrap() >= real_count);
assert!(upper.unwrap() <= data.len() - index);
}
TestResult::passed()
}
}
};
}
// take items from a DEI, taking front for each true and back for each false.
// Return a vector with the concatenation of the fronts and the reverse of the
// backs.
#[cfg(not(miri))]
pub(crate) fn double_ended_take<I, J>(
mut iter: I,
take_side: J,
) -> alloc::vec::Vec<I::Item>
where
I: DoubleEndedIterator,
J: Iterator<Item = bool>,
{
let mut found_front = alloc::vec![];
let mut found_back = alloc::vec![];
for take_front in take_side {
if take_front {
if let Some(pos) = iter.next() {
found_front.push(pos);
} else {
break;
}
} else {
if let Some(pos) = iter.next_back() {
found_back.push(pos);
} else {
break;
}
};
}
let mut all_found = found_front;
all_found.extend(found_back.into_iter().rev());
all_found
}
// return an iterator of the 0-based indices of haystack that match the needle
#[cfg(not(miri))]
pub(crate) fn naive1_iter<'a>(
n1: u8,
haystack: &'a [u8],
) -> impl DoubleEndedIterator<Item = usize> + 'a {
haystack.iter().enumerate().filter(move |&(_, &b)| b == n1).map(|t| t.0)
}
#[cfg(not(miri))]
pub(crate) fn naive2_iter<'a>(
n1: u8,
n2: u8,
haystack: &'a [u8],
) -> impl DoubleEndedIterator<Item = usize> + 'a {
haystack
.iter()
.enumerate()
.filter(move |&(_, &b)| b == n1 || b == n2)
.map(|t| t.0)
}
#[cfg(not(miri))]
pub(crate) fn naive3_iter<'a>(
n1: u8,
n2: u8,
n3: u8,
haystack: &'a [u8],
) -> impl DoubleEndedIterator<Item = usize> + 'a {
haystack
.iter()
.enumerate()
.filter(move |&(_, &b)| b == n1 || b == n2 || b == n3)
.map(|t| t.0)
}

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#[macro_use]
pub(crate) mod memchr;
pub(crate) mod packedpair;
#[macro_use]
pub(crate) mod substring;
// For debugging, particularly in CI, print out the byte order of the current
// target.
#[test]
fn byte_order() {
#[cfg(target_endian = "little")]
std::eprintln!("LITTLE ENDIAN");
#[cfg(target_endian = "big")]
std::eprintln!("BIG ENDIAN");
}

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use alloc::{boxed::Box, vec, vec::Vec};
/// A set of "packed pair" test seeds. Each seed serves as the base for the
/// generation of many other tests. In essence, the seed captures the pair of
/// bytes we used for a predicate and first byte among our needle. The tests
/// generated from each seed essentially vary the length of the needle and
/// haystack, while using the rare/first byte configuration from the seed.
///
/// The purpose of this is to test many different needle/haystack lengths.
/// In particular, some of the vector optimizations might only have bugs
/// in haystacks of a certain size.
const SEEDS: &[Seed] = &[
// Why not use different 'first' bytes? It seemed like a good idea to be
// able to configure it, but when I wrote the test generator below, it
// didn't seem necessary to use for reasons that I forget.
Seed { first: b'x', index1: b'y', index2: b'z' },
Seed { first: b'x', index1: b'x', index2: b'z' },
Seed { first: b'x', index1: b'y', index2: b'x' },
Seed { first: b'x', index1: b'x', index2: b'x' },
Seed { first: b'x', index1: b'y', index2: b'y' },
];
/// Runs a host of "packed pair" search tests.
///
/// These tests specifically look for the occurrence of a possible substring
/// match based on a pair of bytes matching at the right offsets.
pub(crate) struct Runner {
fwd: Option<
Box<
dyn FnMut(&[u8], &[u8], u8, u8) -> Option<Option<usize>> + 'static,
>,
>,
}
impl Runner {
/// Create a new test runner for "packed pair" substring search.
pub(crate) fn new() -> Runner {
Runner { fwd: None }
}
/// Run all tests. This panics on the first failure.
///
/// If the implementation being tested returns `None` for a particular
/// haystack/needle combination, then that test is skipped.
///
/// This runs tests on both the forward and reverse implementations given.
/// If either (or both) are missing, then tests for that implementation are
/// skipped.
pub(crate) fn run(self) {
if let Some(mut fwd) = self.fwd {
for seed in SEEDS.iter() {
for t in seed.generate() {
match fwd(&t.haystack, &t.needle, t.index1, t.index2) {
None => continue,
Some(result) => {
assert_eq!(
t.fwd, result,
"FORWARD, needle: {:?}, haystack: {:?}, \
index1: {:?}, index2: {:?}",
t.needle, t.haystack, t.index1, t.index2,
)
}
}
}
}
}
}
/// Set the implementation for forward "packed pair" substring search.
///
/// If the closure returns `None`, then it is assumed that the given
/// test cannot be applied to the particular implementation and it is
/// skipped. For example, if a particular implementation only supports
/// needles or haystacks for some minimum length.
///
/// If this is not set, then forward "packed pair" search is not tested.
pub(crate) fn fwd(
mut self,
search: impl FnMut(&[u8], &[u8], u8, u8) -> Option<Option<usize>> + 'static,
) -> Runner {
self.fwd = Some(Box::new(search));
self
}
}
/// A test that represents the input and expected output to a "packed pair"
/// search function. The test should be able to run with any "packed pair"
/// implementation and get the expected output.
struct Test {
haystack: Vec<u8>,
needle: Vec<u8>,
index1: u8,
index2: u8,
fwd: Option<usize>,
}
impl Test {
/// Create a new "packed pair" test from a seed and some given offsets to
/// the pair of bytes to use as a predicate in the seed's needle.
///
/// If a valid test could not be constructed, then None is returned.
/// (Currently, we take the approach of massaging tests to be valid
/// instead of rejecting them outright.)
fn new(
seed: Seed,
index1: usize,
index2: usize,
haystack_len: usize,
needle_len: usize,
fwd: Option<usize>,
) -> Option<Test> {
let mut index1: u8 = index1.try_into().unwrap();
let mut index2: u8 = index2.try_into().unwrap();
// The '#' byte is never used in a haystack (unless we're expecting
// a match), while the '@' byte is never used in a needle.
let mut haystack = vec![b'@'; haystack_len];
let mut needle = vec![b'#'; needle_len];
needle[0] = seed.first;
needle[index1 as usize] = seed.index1;
needle[index2 as usize] = seed.index2;
// If we're expecting a match, then make sure the needle occurs
// in the haystack at the expected position.
if let Some(i) = fwd {
haystack[i..i + needle.len()].copy_from_slice(&needle);
}
// If the operations above lead to rare offsets pointing to the
// non-first occurrence of a byte, then adjust it. This might lead
// to redundant tests, but it's simpler than trying to change the
// generation process I think.
if let Some(i) = crate::memchr(seed.index1, &needle) {
index1 = u8::try_from(i).unwrap();
}
if let Some(i) = crate::memchr(seed.index2, &needle) {
index2 = u8::try_from(i).unwrap();
}
Some(Test { haystack, needle, index1, index2, fwd })
}
}
/// Data that describes a single prefilter test seed.
#[derive(Clone, Copy)]
struct Seed {
first: u8,
index1: u8,
index2: u8,
}
impl Seed {
const NEEDLE_LENGTH_LIMIT: usize = {
#[cfg(not(miri))]
{
33
}
#[cfg(miri)]
{
5
}
};
const HAYSTACK_LENGTH_LIMIT: usize = {
#[cfg(not(miri))]
{
65
}
#[cfg(miri)]
{
8
}
};
/// Generate a series of prefilter tests from this seed.
fn generate(self) -> impl Iterator<Item = Test> {
let len_start = 2;
// The iterator below generates *a lot* of tests. The number of
// tests was chosen somewhat empirically to be "bearable" when
// running the test suite.
//
// We use an iterator here because the collective haystacks of all
// these test cases add up to enough memory to OOM a conservative
// sandbox or a small laptop.
(len_start..=Seed::NEEDLE_LENGTH_LIMIT).flat_map(move |needle_len| {
let index_start = len_start - 1;
(index_start..needle_len).flat_map(move |index1| {
(index1..needle_len).flat_map(move |index2| {
(needle_len..=Seed::HAYSTACK_LENGTH_LIMIT).flat_map(
move |haystack_len| {
Test::new(
self,
index1,
index2,
haystack_len,
needle_len,
None,
)
.into_iter()
.chain(
(0..=(haystack_len - needle_len)).flat_map(
move |output| {
Test::new(
self,
index1,
index2,
haystack_len,
needle_len,
Some(output),
)
},
),
)
},
)
})
})
})
}
}

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/*!
This module defines tests and test helpers for substring implementations.
*/
use alloc::{
boxed::Box,
format,
string::{String, ToString},
};
pub(crate) mod naive;
#[macro_use]
pub(crate) mod prop;
const SEEDS: &'static [Seed] = &[
Seed::new("", "", Some(0), Some(0)),
Seed::new("", "a", Some(0), Some(1)),
Seed::new("", "ab", Some(0), Some(2)),
Seed::new("", "abc", Some(0), Some(3)),
Seed::new("a", "", None, None),
Seed::new("a", "a", Some(0), Some(0)),
Seed::new("a", "aa", Some(0), Some(1)),
Seed::new("a", "ba", Some(1), Some(1)),
Seed::new("a", "bba", Some(2), Some(2)),
Seed::new("a", "bbba", Some(3), Some(3)),
Seed::new("a", "bbbab", Some(3), Some(3)),
Seed::new("a", "bbbabb", Some(3), Some(3)),
Seed::new("a", "bbbabbb", Some(3), Some(3)),
Seed::new("a", "bbbbbb", None, None),
Seed::new("ab", "", None, None),
Seed::new("ab", "a", None, None),
Seed::new("ab", "b", None, None),
Seed::new("ab", "ab", Some(0), Some(0)),
Seed::new("ab", "aab", Some(1), Some(1)),
Seed::new("ab", "aaab", Some(2), Some(2)),
Seed::new("ab", "abaab", Some(0), Some(3)),
Seed::new("ab", "baaab", Some(3), Some(3)),
Seed::new("ab", "acb", None, None),
Seed::new("ab", "abba", Some(0), Some(0)),
Seed::new("abc", "ab", None, None),
Seed::new("abc", "abc", Some(0), Some(0)),
Seed::new("abc", "abcz", Some(0), Some(0)),
Seed::new("abc", "abczz", Some(0), Some(0)),
Seed::new("abc", "zabc", Some(1), Some(1)),
Seed::new("abc", "zzabc", Some(2), Some(2)),
Seed::new("abc", "azbc", None, None),
Seed::new("abc", "abzc", None, None),
Seed::new("abczdef", "abczdefzzzzzzzzzzzzzzzzzzzz", Some(0), Some(0)),
Seed::new("abczdef", "zzzzzzzzzzzzzzzzzzzzabczdef", Some(20), Some(20)),
Seed::new(
"xyz",
"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaxyz",
Some(32),
Some(32),
),
Seed::new("\u{0}\u{15}", "\u{0}\u{15}\u{15}\u{0}", Some(0), Some(0)),
Seed::new("\u{0}\u{1e}", "\u{1e}\u{0}", None, None),
];
/// Runs a host of substring search tests.
///
/// This has support for "partial" substring search implementations only work
/// for a subset of needles/haystacks. For example, the "packed pair" substring
/// search implementation only works for haystacks of some minimum length based
/// of the pair of bytes selected and the size of the vector used.
pub(crate) struct Runner {
fwd: Option<
Box<dyn FnMut(&[u8], &[u8]) -> Option<Option<usize>> + 'static>,
>,
rev: Option<
Box<dyn FnMut(&[u8], &[u8]) -> Option<Option<usize>> + 'static>,
>,
}
impl Runner {
/// Create a new test runner for forward and reverse substring search
/// implementations.
pub(crate) fn new() -> Runner {
Runner { fwd: None, rev: None }
}
/// Run all tests. This panics on the first failure.
///
/// If the implementation being tested returns `None` for a particular
/// haystack/needle combination, then that test is skipped.
///
/// This runs tests on both the forward and reverse implementations given.
/// If either (or both) are missing, then tests for that implementation are
/// skipped.
pub(crate) fn run(self) {
if let Some(mut fwd) = self.fwd {
for seed in SEEDS.iter() {
for t in seed.generate() {
match fwd(t.haystack.as_bytes(), t.needle.as_bytes()) {
None => continue,
Some(result) => {
assert_eq!(
t.fwd, result,
"FORWARD, needle: {:?}, haystack: {:?}",
t.needle, t.haystack,
);
}
}
}
}
}
if let Some(mut rev) = self.rev {
for seed in SEEDS.iter() {
for t in seed.generate() {
match rev(t.haystack.as_bytes(), t.needle.as_bytes()) {
None => continue,
Some(result) => {
assert_eq!(
t.rev, result,
"REVERSE, needle: {:?}, haystack: {:?}",
t.needle, t.haystack,
);
}
}
}
}
}
}
/// Set the implementation for forward substring search.
///
/// If the closure returns `None`, then it is assumed that the given
/// test cannot be applied to the particular implementation and it is
/// skipped. For example, if a particular implementation only supports
/// needles or haystacks for some minimum length.
///
/// If this is not set, then forward substring search is not tested.
pub(crate) fn fwd(
mut self,
search: impl FnMut(&[u8], &[u8]) -> Option<Option<usize>> + 'static,
) -> Runner {
self.fwd = Some(Box::new(search));
self
}
/// Set the implementation for reverse substring search.
///
/// If the closure returns `None`, then it is assumed that the given
/// test cannot be applied to the particular implementation and it is
/// skipped. For example, if a particular implementation only supports
/// needles or haystacks for some minimum length.
///
/// If this is not set, then reverse substring search is not tested.
pub(crate) fn rev(
mut self,
search: impl FnMut(&[u8], &[u8]) -> Option<Option<usize>> + 'static,
) -> Runner {
self.rev = Some(Box::new(search));
self
}
}
/// A single substring test for forward and reverse searches.
#[derive(Clone, Debug)]
struct Test {
needle: String,
haystack: String,
fwd: Option<usize>,
rev: Option<usize>,
}
/// A single substring test for forward and reverse searches.
///
/// Each seed is valid on its own, but it also serves as a starting point
/// to generate more tests. Namely, we pad out the haystacks with other
/// characters so that we get more complete coverage. This is especially useful
/// for testing vector algorithms that tend to have weird special cases for
/// alignment and loop unrolling.
///
/// Padding works by assuming certain characters never otherwise appear in a
/// needle or a haystack. Neither should contain a `#` character.
#[derive(Clone, Copy, Debug)]
struct Seed {
needle: &'static str,
haystack: &'static str,
fwd: Option<usize>,
rev: Option<usize>,
}
impl Seed {
const MAX_PAD: usize = 34;
const fn new(
needle: &'static str,
haystack: &'static str,
fwd: Option<usize>,
rev: Option<usize>,
) -> Seed {
Seed { needle, haystack, fwd, rev }
}
fn generate(self) -> impl Iterator<Item = Test> {
assert!(!self.needle.contains('#'), "needle must not contain '#'");
assert!(!self.haystack.contains('#'), "haystack must not contain '#'");
(0..=Seed::MAX_PAD)
// Generate tests for padding at the beginning of haystack.
.map(move |pad| {
let needle = self.needle.to_string();
let prefix = "#".repeat(pad);
let haystack = format!("{}{}", prefix, self.haystack);
let fwd = if needle.is_empty() {
Some(0)
} else {
self.fwd.map(|i| pad + i)
};
let rev = if needle.is_empty() {
Some(haystack.len())
} else {
self.rev.map(|i| pad + i)
};
Test { needle, haystack, fwd, rev }
})
// Generate tests for padding at the end of haystack.
.chain((1..=Seed::MAX_PAD).map(move |pad| {
let needle = self.needle.to_string();
let suffix = "#".repeat(pad);
let haystack = format!("{}{}", self.haystack, suffix);
let fwd = if needle.is_empty() { Some(0) } else { self.fwd };
let rev = if needle.is_empty() {
Some(haystack.len())
} else {
self.rev
};
Test { needle, haystack, fwd, rev }
}))
}
}

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/*!
This module defines "naive" implementations of substring search.
These are sometimes useful to compare with "real" substring implementations.
The idea is that they are so simple that they are unlikely to be incorrect.
*/
/// Naively search forwards for the given needle in the given haystack.
pub(crate) fn find(haystack: &[u8], needle: &[u8]) -> Option<usize> {
let end = haystack.len().checked_sub(needle.len()).map_or(0, |i| i + 1);
for i in 0..end {
if needle == &haystack[i..i + needle.len()] {
return Some(i);
}
}
None
}
/// Naively search in reverse for the given needle in the given haystack.
pub(crate) fn rfind(haystack: &[u8], needle: &[u8]) -> Option<usize> {
let end = haystack.len().checked_sub(needle.len()).map_or(0, |i| i + 1);
for i in (0..end).rev() {
if needle == &haystack[i..i + needle.len()] {
return Some(i);
}
}
None
}
#[cfg(test)]
mod tests {
use crate::tests::substring;
use super::*;
#[test]
fn forward() {
substring::Runner::new().fwd(|h, n| Some(find(h, n))).run()
}
#[test]
fn reverse() {
substring::Runner::new().rev(|h, n| Some(rfind(h, n))).run()
}
}

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/*!
This module defines a few quickcheck properties for substring search.
It also provides a forward and reverse macro for conveniently defining
quickcheck tests that run these properties over any substring search
implementation.
*/
use crate::tests::substring::naive;
/// $fwd is a `impl FnMut(haystack, needle) -> Option<Option<usize>>`. When the
/// routine returns `None`, then it's skipped, which is useful for substring
/// implementations that don't work for all inputs.
#[macro_export]
macro_rules! define_substring_forward_quickcheck {
($fwd:expr) => {
#[cfg(not(miri))]
quickcheck::quickcheck! {
fn qc_fwd_prefix_is_substring(bs: alloc::vec::Vec<u8>) -> bool {
crate::tests::substring::prop::prefix_is_substring(&bs, $fwd)
}
fn qc_fwd_suffix_is_substring(bs: alloc::vec::Vec<u8>) -> bool {
crate::tests::substring::prop::suffix_is_substring(&bs, $fwd)
}
fn qc_fwd_matches_naive(
haystack: alloc::vec::Vec<u8>,
needle: alloc::vec::Vec<u8>
) -> bool {
crate::tests::substring::prop::same_as_naive(
false,
&haystack,
&needle,
$fwd,
)
}
}
};
}
/// $rev is a `impl FnMut(haystack, needle) -> Option<Option<usize>>`. When the
/// routine returns `None`, then it's skipped, which is useful for substring
/// implementations that don't work for all inputs.
#[macro_export]
macro_rules! define_substring_reverse_quickcheck {
($rev:expr) => {
#[cfg(not(miri))]
quickcheck::quickcheck! {
fn qc_rev_prefix_is_substring(bs: alloc::vec::Vec<u8>) -> bool {
crate::tests::substring::prop::prefix_is_substring(&bs, $rev)
}
fn qc_rev_suffix_is_substring(bs: alloc::vec::Vec<u8>) -> bool {
crate::tests::substring::prop::suffix_is_substring(&bs, $rev)
}
fn qc_rev_matches_naive(
haystack: alloc::vec::Vec<u8>,
needle: alloc::vec::Vec<u8>
) -> bool {
crate::tests::substring::prop::same_as_naive(
true,
&haystack,
&needle,
$rev,
)
}
}
};
}
/// Check that every prefix of the given byte string is a substring.
pub(crate) fn prefix_is_substring(
bs: &[u8],
mut search: impl FnMut(&[u8], &[u8]) -> Option<Option<usize>>,
) -> bool {
for i in 0..bs.len().saturating_sub(1) {
let prefix = &bs[..i];
let result = match search(bs, prefix) {
None => continue,
Some(result) => result,
};
if !result.is_some() {
return false;
}
}
true
}
/// Check that every suffix of the given byte string is a substring.
pub(crate) fn suffix_is_substring(
bs: &[u8],
mut search: impl FnMut(&[u8], &[u8]) -> Option<Option<usize>>,
) -> bool {
for i in 0..bs.len().saturating_sub(1) {
let suffix = &bs[i..];
let result = match search(bs, suffix) {
None => continue,
Some(result) => result,
};
if !result.is_some() {
return false;
}
}
true
}
/// Check that naive substring search matches the result of the given search
/// algorithm.
pub(crate) fn same_as_naive(
reverse: bool,
haystack: &[u8],
needle: &[u8],
mut search: impl FnMut(&[u8], &[u8]) -> Option<Option<usize>>,
) -> bool {
let result = match search(haystack, needle) {
None => return true,
Some(result) => result,
};
if reverse {
result == naive::rfind(haystack, needle)
} else {
result == naive::find(haystack, needle)
}
}

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vendor/memchr/src/tests/x86_64-soft_float.json vendored Normal file
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@ -0,0 +1,15 @@
{
"llvm-target": "x86_64-unknown-none",
"target-endian": "little",
"target-pointer-width": "64",
"target-c-int-width": "32",
"os": "none",
"arch": "x86_64",
"data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128",
"linker-flavor": "ld.lld",
"linker": "rust-lld",
"features": "-mmx,-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-3dnow,-3dnowa,-avx,-avx2,+soft-float",
"executables": true,
"disable-redzone": true,
"panic-strategy": "abort"
}

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vendor/memchr/src/vector.rs vendored Normal file
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/// A trait for describing vector operations used by vectorized searchers.
///
/// The trait is highly constrained to low level vector operations needed.
/// In general, it was invented mostly to be generic over x86's __m128i and
/// __m256i types. At time of writing, it also supports wasm and aarch64
/// 128-bit vector types as well.
///
/// # Safety
///
/// All methods are not safe since they are intended to be implemented using
/// vendor intrinsics, which are also not safe. Callers must ensure that the
/// appropriate target features are enabled in the calling function, and that
/// the current CPU supports them. All implementations should avoid marking the
/// routines with #[target_feature] and instead mark them as #[inline(always)]
/// to ensure they get appropriately inlined. (inline(always) cannot be used
/// with target_feature.)
pub(crate) trait Vector: Copy + core::fmt::Debug {
/// The number of bits in the vector.
const BITS: usize;
/// The number of bytes in the vector. That is, this is the size of the
/// vector in memory.
const BYTES: usize;
/// The bits that must be zero in order for a `*const u8` pointer to be
/// correctly aligned to read vector values.
const ALIGN: usize;
/// The type of the value returned by `Vector::movemask`.
///
/// This supports abstracting over the specific representation used in
/// order to accommodate different representations in different ISAs.
type Mask: MoveMask;
/// Create a vector with 8-bit lanes with the given byte repeated into each
/// lane.
unsafe fn splat(byte: u8) -> Self;
/// Read a vector-size number of bytes from the given pointer. The pointer
/// must be aligned to the size of the vector.
///
/// # Safety
///
/// Callers must guarantee that at least `BYTES` bytes are readable from
/// `data` and that `data` is aligned to a `BYTES` boundary.
unsafe fn load_aligned(data: *const u8) -> Self;
/// Read a vector-size number of bytes from the given pointer. The pointer
/// does not need to be aligned.
///
/// # Safety
///
/// Callers must guarantee that at least `BYTES` bytes are readable from
/// `data`.
unsafe fn load_unaligned(data: *const u8) -> Self;
/// _mm_movemask_epi8 or _mm256_movemask_epi8
unsafe fn movemask(self) -> Self::Mask;
/// _mm_cmpeq_epi8 or _mm256_cmpeq_epi8
unsafe fn cmpeq(self, vector2: Self) -> Self;
/// _mm_and_si128 or _mm256_and_si256
unsafe fn and(self, vector2: Self) -> Self;
/// _mm_or or _mm256_or_si256
unsafe fn or(self, vector2: Self) -> Self;
/// Returns true if and only if `Self::movemask` would return a mask that
/// contains at least one non-zero bit.
unsafe fn movemask_will_have_non_zero(self) -> bool {
self.movemask().has_non_zero()
}
}
/// A trait that abstracts over a vector-to-scalar operation called
/// "move mask."
///
/// On x86-64, this is `_mm_movemask_epi8` for SSE2 and `_mm256_movemask_epi8`
/// for AVX2. It takes a vector of `u8` lanes and returns a scalar where the
/// `i`th bit is set if and only if the most significant bit in the `i`th lane
/// of the vector is set. The simd128 ISA for wasm32 also supports this
/// exact same operation natively.
///
/// ... But aarch64 doesn't. So we have to fake it with more instructions and
/// a slightly different representation. We could do extra work to unify the
/// representations, but then would require additional costs in the hot path
/// for `memchr` and `packedpair`. So instead, we abstraction over the specific
/// representation with this trait an ddefine the operations we actually need.
pub(crate) trait MoveMask: Copy + core::fmt::Debug {
/// Return a mask that is all zeros except for the least significant `n`
/// lanes in a corresponding vector.
fn all_zeros_except_least_significant(n: usize) -> Self;
/// Returns true if and only if this mask has a a non-zero bit anywhere.
fn has_non_zero(self) -> bool;
/// Returns the number of bits set to 1 in this mask.
fn count_ones(self) -> usize;
/// Does a bitwise `and` operation between `self` and `other`.
fn and(self, other: Self) -> Self;
/// Does a bitwise `or` operation between `self` and `other`.
fn or(self, other: Self) -> Self;
/// Returns a mask that is equivalent to `self` but with the least
/// significant 1-bit set to 0.
fn clear_least_significant_bit(self) -> Self;
/// Returns the offset of the first non-zero lane this mask represents.
fn first_offset(self) -> usize;
/// Returns the offset of the last non-zero lane this mask represents.
fn last_offset(self) -> usize;
}
/// This is a "sensible" movemask implementation where each bit represents
/// whether the most significant bit is set in each corresponding lane of a
/// vector. This is used on x86-64 and wasm, but such a mask is more expensive
/// to get on aarch64 so we use something a little different.
///
/// We call this "sensible" because this is what we get using native sse/avx
/// movemask instructions. But neon has no such native equivalent.
#[derive(Clone, Copy, Debug)]
pub(crate) struct SensibleMoveMask(u32);
impl SensibleMoveMask {
/// Get the mask in a form suitable for computing offsets.
///
/// Basically, this normalizes to little endian. On big endian, this swaps
/// the bytes.
#[inline(always)]
fn get_for_offset(self) -> u32 {
#[cfg(target_endian = "big")]
{
self.0.swap_bytes()
}
#[cfg(target_endian = "little")]
{
self.0
}
}
}
impl MoveMask for SensibleMoveMask {
#[inline(always)]
fn all_zeros_except_least_significant(n: usize) -> SensibleMoveMask {
debug_assert!(n < 32);
SensibleMoveMask(!((1 << n) - 1))
}
#[inline(always)]
fn has_non_zero(self) -> bool {
self.0 != 0
}
#[inline(always)]
fn count_ones(self) -> usize {
self.0.count_ones() as usize
}
#[inline(always)]
fn and(self, other: SensibleMoveMask) -> SensibleMoveMask {
SensibleMoveMask(self.0 & other.0)
}
#[inline(always)]
fn or(self, other: SensibleMoveMask) -> SensibleMoveMask {
SensibleMoveMask(self.0 | other.0)
}
#[inline(always)]
fn clear_least_significant_bit(self) -> SensibleMoveMask {
SensibleMoveMask(self.0 & (self.0 - 1))
}
#[inline(always)]
fn first_offset(self) -> usize {
// We are dealing with little endian here (and if we aren't, we swap
// the bytes so we are in practice), where the most significant byte
// is at a higher address. That means the least significant bit that
// is set corresponds to the position of our first matching byte.
// That position corresponds to the number of zeros after the least
// significant bit.
self.get_for_offset().trailing_zeros() as usize
}
#[inline(always)]
fn last_offset(self) -> usize {
// We are dealing with little endian here (and if we aren't, we swap
// the bytes so we are in practice), where the most significant byte is
// at a higher address. That means the most significant bit that is set
// corresponds to the position of our last matching byte. The position
// from the end of the mask is therefore the number of leading zeros
// in a 32 bit integer, and the position from the start of the mask is
// therefore 32 - (leading zeros) - 1.
32 - self.get_for_offset().leading_zeros() as usize - 1
}
}
#[cfg(target_arch = "x86_64")]
mod x86sse2 {
use core::arch::x86_64::*;
use super::{SensibleMoveMask, Vector};
impl Vector for __m128i {
const BITS: usize = 128;
const BYTES: usize = 16;
const ALIGN: usize = Self::BYTES - 1;
type Mask = SensibleMoveMask;
#[inline(always)]
unsafe fn splat(byte: u8) -> __m128i {
_mm_set1_epi8(byte as i8)
}
#[inline(always)]
unsafe fn load_aligned(data: *const u8) -> __m128i {
_mm_load_si128(data as *const __m128i)
}
#[inline(always)]
unsafe fn load_unaligned(data: *const u8) -> __m128i {
_mm_loadu_si128(data as *const __m128i)
}
#[inline(always)]
unsafe fn movemask(self) -> SensibleMoveMask {
SensibleMoveMask(_mm_movemask_epi8(self) as u32)
}
#[inline(always)]
unsafe fn cmpeq(self, vector2: Self) -> __m128i {
_mm_cmpeq_epi8(self, vector2)
}
#[inline(always)]
unsafe fn and(self, vector2: Self) -> __m128i {
_mm_and_si128(self, vector2)
}
#[inline(always)]
unsafe fn or(self, vector2: Self) -> __m128i {
_mm_or_si128(self, vector2)
}
}
}
#[cfg(target_arch = "x86_64")]
mod x86avx2 {
use core::arch::x86_64::*;
use super::{SensibleMoveMask, Vector};
impl Vector for __m256i {
const BITS: usize = 256;
const BYTES: usize = 32;
const ALIGN: usize = Self::BYTES - 1;
type Mask = SensibleMoveMask;
#[inline(always)]
unsafe fn splat(byte: u8) -> __m256i {
_mm256_set1_epi8(byte as i8)
}
#[inline(always)]
unsafe fn load_aligned(data: *const u8) -> __m256i {
_mm256_load_si256(data as *const __m256i)
}
#[inline(always)]
unsafe fn load_unaligned(data: *const u8) -> __m256i {
_mm256_loadu_si256(data as *const __m256i)
}
#[inline(always)]
unsafe fn movemask(self) -> SensibleMoveMask {
SensibleMoveMask(_mm256_movemask_epi8(self) as u32)
}
#[inline(always)]
unsafe fn cmpeq(self, vector2: Self) -> __m256i {
_mm256_cmpeq_epi8(self, vector2)
}
#[inline(always)]
unsafe fn and(self, vector2: Self) -> __m256i {
_mm256_and_si256(self, vector2)
}
#[inline(always)]
unsafe fn or(self, vector2: Self) -> __m256i {
_mm256_or_si256(self, vector2)
}
}
}
#[cfg(target_arch = "aarch64")]
mod aarch64neon {
use core::arch::aarch64::*;
use super::{MoveMask, Vector};
impl Vector for uint8x16_t {
const BITS: usize = 128;
const BYTES: usize = 16;
const ALIGN: usize = Self::BYTES - 1;
type Mask = NeonMoveMask;
#[inline(always)]
unsafe fn splat(byte: u8) -> uint8x16_t {
vdupq_n_u8(byte)
}
#[inline(always)]
unsafe fn load_aligned(data: *const u8) -> uint8x16_t {
// I've tried `data.cast::<uint8x16_t>().read()` instead, but
// couldn't observe any benchmark differences.
Self::load_unaligned(data)
}
#[inline(always)]
unsafe fn load_unaligned(data: *const u8) -> uint8x16_t {
vld1q_u8(data)
}
#[inline(always)]
unsafe fn movemask(self) -> NeonMoveMask {
let asu16s = vreinterpretq_u16_u8(self);
let mask = vshrn_n_u16(asu16s, 4);
let asu64 = vreinterpret_u64_u8(mask);
let scalar64 = vget_lane_u64(asu64, 0);
NeonMoveMask(scalar64 & 0x8888888888888888)
}
#[inline(always)]
unsafe fn cmpeq(self, vector2: Self) -> uint8x16_t {
vceqq_u8(self, vector2)
}
#[inline(always)]
unsafe fn and(self, vector2: Self) -> uint8x16_t {
vandq_u8(self, vector2)
}
#[inline(always)]
unsafe fn or(self, vector2: Self) -> uint8x16_t {
vorrq_u8(self, vector2)
}
/// This is the only interesting implementation of this routine.
/// Basically, instead of doing the "shift right narrow" dance, we use
/// adajacent folding max to determine whether there are any non-zero
/// bytes in our mask. If there are, *then* we'll do the "shift right
/// narrow" dance. In benchmarks, this does lead to slightly better
/// throughput, but the win doesn't appear huge.
#[inline(always)]
unsafe fn movemask_will_have_non_zero(self) -> bool {
let low = vreinterpretq_u64_u8(vpmaxq_u8(self, self));
vgetq_lane_u64(low, 0) != 0
}
}
/// Neon doesn't have a `movemask` that works like the one in x86-64, so we
/// wind up using a different method[1]. The different method also produces
/// a mask, but 4 bits are set in the neon case instead of a single bit set
/// in the x86-64 case. We do an extra step to zero out 3 of the 4 bits,
/// but we still wind up with at least 3 zeroes between each set bit. This
/// generally means that we need to do some division by 4 before extracting
/// offsets.
///
/// In fact, the existence of this type is the entire reason that we have
/// the `MoveMask` trait in the first place. This basically lets us keep
/// the different representations of masks without being forced to unify
/// them into a single representation, which could result in extra and
/// unnecessary work.
///
/// [1]: https://community.arm.com/arm-community-blogs/b/infrastructure-solutions-blog/posts/porting-x86-vector-bitmask-optimizations-to-arm-neon
#[derive(Clone, Copy, Debug)]
pub(crate) struct NeonMoveMask(u64);
impl NeonMoveMask {
/// Get the mask in a form suitable for computing offsets.
///
/// Basically, this normalizes to little endian. On big endian, this
/// swaps the bytes.
#[inline(always)]
fn get_for_offset(self) -> u64 {
#[cfg(target_endian = "big")]
{
self.0.swap_bytes()
}
#[cfg(target_endian = "little")]
{
self.0
}
}
}
impl MoveMask for NeonMoveMask {
#[inline(always)]
fn all_zeros_except_least_significant(n: usize) -> NeonMoveMask {
debug_assert!(n < 16);
NeonMoveMask(!(((1 << n) << 2) - 1))
}
#[inline(always)]
fn has_non_zero(self) -> bool {
self.0 != 0
}
#[inline(always)]
fn count_ones(self) -> usize {
self.0.count_ones() as usize
}
#[inline(always)]
fn and(self, other: NeonMoveMask) -> NeonMoveMask {
NeonMoveMask(self.0 & other.0)
}
#[inline(always)]
fn or(self, other: NeonMoveMask) -> NeonMoveMask {
NeonMoveMask(self.0 | other.0)
}
#[inline(always)]
fn clear_least_significant_bit(self) -> NeonMoveMask {
NeonMoveMask(self.0 & (self.0 - 1))
}
#[inline(always)]
fn first_offset(self) -> usize {
// We are dealing with little endian here (and if we aren't,
// we swap the bytes so we are in practice), where the most
// significant byte is at a higher address. That means the least
// significant bit that is set corresponds to the position of our
// first matching byte. That position corresponds to the number of
// zeros after the least significant bit.
//
// Note that unlike `SensibleMoveMask`, this mask has its bits
// spread out over 64 bits instead of 16 bits (for a 128 bit
// vector). Namely, where as x86-64 will turn
//
// 0x00 0xFF 0x00 0x00 0xFF
//
// into 10010, our neon approach will turn it into
//
// 10000000000010000000
//
// And this happens because neon doesn't have a native `movemask`
// instruction, so we kind of fake it[1]. Thus, we divide the
// number of trailing zeros by 4 to get the "real" offset.
//
// [1]: https://community.arm.com/arm-community-blogs/b/infrastructure-solutions-blog/posts/porting-x86-vector-bitmask-optimizations-to-arm-neon
(self.get_for_offset().trailing_zeros() >> 2) as usize
}
#[inline(always)]
fn last_offset(self) -> usize {
// See comment in `first_offset` above. This is basically the same,
// but coming from the other direction.
16 - (self.get_for_offset().leading_zeros() >> 2) as usize - 1
}
}
}
#[cfg(target_arch = "wasm32")]
mod wasm_simd128 {
use core::arch::wasm32::*;
use super::{SensibleMoveMask, Vector};
impl Vector for v128 {
const BITS: usize = 128;
const BYTES: usize = 16;
const ALIGN: usize = Self::BYTES - 1;
type Mask = SensibleMoveMask;
#[inline(always)]
unsafe fn splat(byte: u8) -> v128 {
u8x16_splat(byte)
}
#[inline(always)]
unsafe fn load_aligned(data: *const u8) -> v128 {
*data.cast()
}
#[inline(always)]
unsafe fn load_unaligned(data: *const u8) -> v128 {
v128_load(data.cast())
}
#[inline(always)]
unsafe fn movemask(self) -> SensibleMoveMask {
SensibleMoveMask(u8x16_bitmask(self).into())
}
#[inline(always)]
unsafe fn cmpeq(self, vector2: Self) -> v128 {
u8x16_eq(self, vector2)
}
#[inline(always)]
unsafe fn and(self, vector2: Self) -> v128 {
v128_and(self, vector2)
}
#[inline(always)]
unsafe fn or(self, vector2: Self) -> v128 {
v128_or(self, vector2)
}
}
}