114 lines
3.6 KiB
Rust
114 lines
3.6 KiB
Rust
// Translated from C to Rust. The original C code can be found at
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// https://github.com/ulfjack/ryu and carries the following license:
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//
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// Copyright 2018 Ulf Adams
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//
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// The contents of this file may be used under the terms of the Apache License,
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// Version 2.0.
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//
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// (See accompanying file LICENSE-Apache or copy at
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// http://www.apache.org/licenses/LICENSE-2.0)
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//
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// Alternatively, the contents of this file may be used under the terms of
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// the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE-Boost or copy at
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// https://www.boost.org/LICENSE_1_0.txt)
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//
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// Unless required by applicable law or agreed to in writing, this software
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// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, either express or implied.
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use crate::d2s;
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pub const FLOAT_POW5_INV_BITCOUNT: i32 = d2s::DOUBLE_POW5_INV_BITCOUNT - 64;
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pub const FLOAT_POW5_BITCOUNT: i32 = d2s::DOUBLE_POW5_BITCOUNT - 64;
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#[cfg_attr(feature = "no-panic", inline)]
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fn pow5factor_32(mut value: u32) -> u32 {
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let mut count = 0u32;
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loop {
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debug_assert!(value != 0);
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let q = value / 5;
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let r = value % 5;
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if r != 0 {
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break;
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}
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value = q;
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count += 1;
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}
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count
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}
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// Returns true if value is divisible by 5^p.
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#[cfg_attr(feature = "no-panic", inline)]
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pub fn multiple_of_power_of_5_32(value: u32, p: u32) -> bool {
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pow5factor_32(value) >= p
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}
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// Returns true if value is divisible by 2^p.
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#[cfg_attr(feature = "no-panic", inline)]
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pub fn multiple_of_power_of_2_32(value: u32, p: u32) -> bool {
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// __builtin_ctz doesn't appear to be faster here.
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(value & ((1u32 << p) - 1)) == 0
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}
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// It seems to be slightly faster to avoid uint128_t here, although the
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// generated code for uint128_t looks slightly nicer.
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#[cfg_attr(feature = "no-panic", inline)]
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fn mul_shift_32(m: u32, factor: u64, shift: i32) -> u32 {
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debug_assert!(shift > 32);
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// The casts here help MSVC to avoid calls to the __allmul library
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// function.
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let factor_lo = factor as u32;
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let factor_hi = (factor >> 32) as u32;
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let bits0 = m as u64 * factor_lo as u64;
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let bits1 = m as u64 * factor_hi as u64;
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let sum = (bits0 >> 32) + bits1;
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let shifted_sum = sum >> (shift - 32);
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debug_assert!(shifted_sum <= u32::max_value() as u64);
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shifted_sum as u32
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}
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#[cfg_attr(feature = "no-panic", inline)]
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pub fn mul_pow5_inv_div_pow2(m: u32, q: u32, j: i32) -> u32 {
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#[cfg(feature = "small")]
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{
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// The inverse multipliers are defined as [2^x / 5^y] + 1; the upper 64
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// bits from the double lookup table are the correct bits for [2^x /
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// 5^y], so we have to add 1 here. Note that we rely on the fact that
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// the added 1 that's already stored in the table never overflows into
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// the upper 64 bits.
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let pow5 = unsafe { d2s::compute_inv_pow5(q) };
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mul_shift_32(m, pow5.1 + 1, j)
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}
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#[cfg(not(feature = "small"))]
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{
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debug_assert!(q < d2s::DOUBLE_POW5_INV_SPLIT.len() as u32);
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unsafe {
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mul_shift_32(
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m,
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d2s::DOUBLE_POW5_INV_SPLIT.get_unchecked(q as usize).1 + 1,
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j,
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)
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}
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}
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}
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#[cfg_attr(feature = "no-panic", inline)]
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pub fn mul_pow5_div_pow2(m: u32, i: u32, j: i32) -> u32 {
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#[cfg(feature = "small")]
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{
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let pow5 = unsafe { d2s::compute_pow5(i) };
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mul_shift_32(m, pow5.1, j)
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}
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#[cfg(not(feature = "small"))]
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{
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debug_assert!(i < d2s::DOUBLE_POW5_SPLIT.len() as u32);
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unsafe { mul_shift_32(m, d2s::DOUBLE_POW5_SPLIT.get_unchecked(i as usize).1, j) }
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}
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}
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