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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
parent 5ecd8cf2cb
commit 1b6a04ca55
7309 changed files with 2160054 additions and 0 deletions
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vendor/bytemuck/src/allocation.rs vendored Normal file
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#![cfg(feature = "extern_crate_alloc")]
//! Stuff to boost things in the `alloc` crate.
//!
//! * You must enable the `extern_crate_alloc` feature of `bytemuck` or you will
//! not be able to use this module! This is generally done by adding the
//! feature to the dependency in Cargo.toml like so:
//!
//! `bytemuck = { version = "VERSION_YOU_ARE_USING", features =
//! ["extern_crate_alloc"]}`
use super::*;
#[cfg(target_has_atomic = "ptr")]
use alloc::sync::Arc;
use alloc::{
alloc::{alloc_zeroed, Layout},
boxed::Box,
rc::Rc,
vec,
vec::Vec,
};
/// As [`try_cast_box`](try_cast_box), but unwraps for you.
#[inline]
pub fn cast_box<A: NoUninit, B: AnyBitPattern>(input: Box<A>) -> Box<B> {
try_cast_box(input).map_err(|(e, _v)| e).unwrap()
}
/// Attempts to cast the content type of a [`Box`](alloc::boxed::Box).
///
/// On failure you get back an error along with the starting `Box`.
///
/// ## Failure
///
/// * The start and end content type of the `Box` must have the exact same
/// alignment.
/// * The start and end size of the `Box` must have the exact same size.
#[inline]
pub fn try_cast_box<A: NoUninit, B: AnyBitPattern>(
input: Box<A>,
) -> Result<Box<B>, (PodCastError, Box<A>)> {
if align_of::<A>() != align_of::<B>() {
Err((PodCastError::AlignmentMismatch, input))
} else if size_of::<A>() != size_of::<B>() {
Err((PodCastError::SizeMismatch, input))
} else {
// Note(Lokathor): This is much simpler than with the Vec casting!
let ptr: *mut B = Box::into_raw(input) as *mut B;
Ok(unsafe { Box::from_raw(ptr) })
}
}
/// Allocates a `Box<T>` with all of the contents being zeroed out.
///
/// This uses the global allocator to create a zeroed allocation and _then_
/// turns it into a Box. In other words, it's 100% assured that the zeroed data
/// won't be put temporarily on the stack. You can make a box of any size
/// without fear of a stack overflow.
///
/// ## Failure
///
/// This fails if the allocation fails.
#[inline]
pub fn try_zeroed_box<T: Zeroable>() -> Result<Box<T>, ()> {
if size_of::<T>() == 0 {
// This will not allocate but simply create a dangling pointer.
let dangling = core::ptr::NonNull::dangling().as_ptr();
return Ok(unsafe { Box::from_raw(dangling) });
}
let layout = Layout::new::<T>();
let ptr = unsafe { alloc_zeroed(layout) };
if ptr.is_null() {
// we don't know what the error is because `alloc_zeroed` is a dumb API
Err(())
} else {
Ok(unsafe { Box::<T>::from_raw(ptr as *mut T) })
}
}
/// As [`try_zeroed_box`], but unwraps for you.
#[inline]
pub fn zeroed_box<T: Zeroable>() -> Box<T> {
try_zeroed_box().unwrap()
}
/// Allocates a `Vec<T>` of length and capacity exactly equal to `length` and
/// all elements zeroed.
///
/// ## Failure
///
/// This fails if the allocation fails, or if a layout cannot be calculated for
/// the allocation.
pub fn try_zeroed_vec<T: Zeroable>(length: usize) -> Result<Vec<T>, ()> {
if length == 0 {
Ok(Vec::new())
} else {
let boxed_slice = try_zeroed_slice_box(length)?;
Ok(boxed_slice.into_vec())
}
}
/// As [`try_zeroed_vec`] but unwraps for you
pub fn zeroed_vec<T: Zeroable>(length: usize) -> Vec<T> {
try_zeroed_vec(length).unwrap()
}
/// Allocates a `Box<[T]>` with all contents being zeroed out.
///
/// This uses the global allocator to create a zeroed allocation and _then_
/// turns it into a Box. In other words, it's 100% assured that the zeroed data
/// won't be put temporarily on the stack. You can make a box of any size
/// without fear of a stack overflow.
///
/// ## Failure
///
/// This fails if the allocation fails, or if a layout cannot be calculated for
/// the allocation.
#[inline]
pub fn try_zeroed_slice_box<T: Zeroable>(
length: usize,
) -> Result<Box<[T]>, ()> {
if size_of::<T>() == 0 || length == 0 {
// This will not allocate but simply create a dangling slice pointer.
let dangling = core::ptr::NonNull::dangling().as_ptr();
let dangling_slice = core::ptr::slice_from_raw_parts_mut(dangling, length);
return Ok(unsafe { Box::from_raw(dangling_slice) });
}
let layout = core::alloc::Layout::array::<T>(length).map_err(|_| ())?;
let ptr = unsafe { alloc_zeroed(layout) };
if ptr.is_null() {
// we don't know what the error is because `alloc_zeroed` is a dumb API
Err(())
} else {
let slice =
unsafe { core::slice::from_raw_parts_mut(ptr as *mut T, length) };
Ok(unsafe { Box::<[T]>::from_raw(slice) })
}
}
/// As [`try_zeroed_slice_box`](try_zeroed_slice_box), but unwraps for you.
pub fn zeroed_slice_box<T: Zeroable>(length: usize) -> Box<[T]> {
try_zeroed_slice_box(length).unwrap()
}
/// As [`try_cast_slice_box`](try_cast_slice_box), but unwraps for you.
#[inline]
pub fn cast_slice_box<A: NoUninit, B: AnyBitPattern>(
input: Box<[A]>,
) -> Box<[B]> {
try_cast_slice_box(input).map_err(|(e, _v)| e).unwrap()
}
/// Attempts to cast the content type of a `Box<[T]>`.
///
/// On failure you get back an error along with the starting `Box<[T]>`.
///
/// ## Failure
///
/// * The start and end content type of the `Box<[T]>` must have the exact same
/// alignment.
/// * The start and end content size in bytes of the `Box<[T]>` must be the
/// exact same.
#[inline]
pub fn try_cast_slice_box<A: NoUninit, B: AnyBitPattern>(
input: Box<[A]>,
) -> Result<Box<[B]>, (PodCastError, Box<[A]>)> {
if align_of::<A>() != align_of::<B>() {
Err((PodCastError::AlignmentMismatch, input))
} else if size_of::<A>() != size_of::<B>() {
if size_of::<A>() * input.len() % size_of::<B>() != 0 {
// If the size in bytes of the underlying buffer does not match an exact
// multiple of the size of B, we cannot cast between them.
Err((PodCastError::SizeMismatch, input))
} else {
// Because the size is an exact multiple, we can now change the length
// of the slice and recreate the Box
// NOTE: This is a valid operation because according to the docs of
// std::alloc::GlobalAlloc::dealloc(), the Layout that was used to alloc
// the block must be the same Layout that is used to dealloc the block.
// Luckily, Layout only stores two things, the alignment, and the size in
// bytes. So as long as both of those stay the same, the Layout will
// remain a valid input to dealloc.
let length = size_of::<A>() * input.len() / size_of::<B>();
let box_ptr: *mut A = Box::into_raw(input) as *mut A;
let ptr: *mut [B] =
unsafe { core::slice::from_raw_parts_mut(box_ptr as *mut B, length) };
Ok(unsafe { Box::<[B]>::from_raw(ptr) })
}
} else {
let box_ptr: *mut [A] = Box::into_raw(input);
let ptr: *mut [B] = box_ptr as *mut [B];
Ok(unsafe { Box::<[B]>::from_raw(ptr) })
}
}
/// As [`try_cast_vec`](try_cast_vec), but unwraps for you.
#[inline]
pub fn cast_vec<A: NoUninit, B: AnyBitPattern>(input: Vec<A>) -> Vec<B> {
try_cast_vec(input).map_err(|(e, _v)| e).unwrap()
}
/// Attempts to cast the content type of a [`Vec`](alloc::vec::Vec).
///
/// On failure you get back an error along with the starting `Vec`.
///
/// ## Failure
///
/// * The start and end content type of the `Vec` must have the exact same
/// alignment.
/// * The start and end content size in bytes of the `Vec` must be the exact
/// same.
/// * The start and end capacity in bytes of the `Vec` must be the exact same.
#[inline]
pub fn try_cast_vec<A: NoUninit, B: AnyBitPattern>(
input: Vec<A>,
) -> Result<Vec<B>, (PodCastError, Vec<A>)> {
if align_of::<A>() != align_of::<B>() {
Err((PodCastError::AlignmentMismatch, input))
} else if size_of::<A>() != size_of::<B>() {
if size_of::<A>() * input.len() % size_of::<B>() != 0
|| size_of::<A>() * input.capacity() % size_of::<B>() != 0
{
// If the size in bytes of the underlying buffer does not match an exact
// multiple of the size of B, we cannot cast between them.
// Note that we have to pay special attention to make sure that both
// length and capacity are valid under B, as we do not want to
// change which bytes are considered part of the initialized slice
// of the Vec
Err((PodCastError::SizeMismatch, input))
} else {
// Because the size is an exact multiple, we can now change the length and
// capacity and recreate the Vec
// NOTE: This is a valid operation because according to the docs of
// std::alloc::GlobalAlloc::dealloc(), the Layout that was used to alloc
// the block must be the same Layout that is used to dealloc the block.
// Luckily, Layout only stores two things, the alignment, and the size in
// bytes. So as long as both of those stay the same, the Layout will
// remain a valid input to dealloc.
// Note(Lokathor): First we record the length and capacity, which don't
// have any secret provenance metadata.
let length: usize = size_of::<A>() * input.len() / size_of::<B>();
let capacity: usize = size_of::<A>() * input.capacity() / size_of::<B>();
// Note(Lokathor): Next we "pre-forget" the old Vec by wrapping with
// ManuallyDrop, because if we used `core::mem::forget` after taking the
// pointer then that would invalidate our pointer. In nightly there's a
// "into raw parts" method, which we can switch this too eventually.
let mut manual_drop_vec = ManuallyDrop::new(input);
let vec_ptr: *mut A = manual_drop_vec.as_mut_ptr();
let ptr: *mut B = vec_ptr as *mut B;
Ok(unsafe { Vec::from_raw_parts(ptr, length, capacity) })
}
} else {
// Note(Lokathor): First we record the length and capacity, which don't have
// any secret provenance metadata.
let length: usize = input.len();
let capacity: usize = input.capacity();
// Note(Lokathor): Next we "pre-forget" the old Vec by wrapping with
// ManuallyDrop, because if we used `core::mem::forget` after taking the
// pointer then that would invalidate our pointer. In nightly there's a
// "into raw parts" method, which we can switch this too eventually.
let mut manual_drop_vec = ManuallyDrop::new(input);
let vec_ptr: *mut A = manual_drop_vec.as_mut_ptr();
let ptr: *mut B = vec_ptr as *mut B;
Ok(unsafe { Vec::from_raw_parts(ptr, length, capacity) })
}
}
/// This "collects" a slice of pod data into a vec of a different pod type.
///
/// Unlike with [`cast_slice`] and [`cast_slice_mut`], this will always work.
///
/// The output vec will be of a minimal size/capacity to hold the slice given.
///
/// ```rust
/// # use bytemuck::*;
/// let halfwords: [u16; 4] = [5, 6, 7, 8];
/// let vec_of_words: Vec<u32> = pod_collect_to_vec(&halfwords);
/// if cfg!(target_endian = "little") {
/// assert_eq!(&vec_of_words[..], &[0x0006_0005, 0x0008_0007][..])
/// } else {
/// assert_eq!(&vec_of_words[..], &[0x0005_0006, 0x0007_0008][..])
/// }
/// ```
pub fn pod_collect_to_vec<A: NoUninit, B: NoUninit + AnyBitPattern>(
src: &[A],
) -> Vec<B> {
let src_size = size_of_val(src);
// Note(Lokathor): dst_count is rounded up so that the dest will always be at
// least as many bytes as the src.
let dst_count = src_size / size_of::<B>()
+ if src_size % size_of::<B>() != 0 { 1 } else { 0 };
let mut dst = vec![B::zeroed(); dst_count];
let src_bytes: &[u8] = cast_slice(src);
let dst_bytes: &mut [u8] = cast_slice_mut(&mut dst[..]);
dst_bytes[..src_size].copy_from_slice(src_bytes);
dst
}
/// As [`try_cast_rc`](try_cast_rc), but unwraps for you.
#[inline]
pub fn cast_rc<A: NoUninit + AnyBitPattern, B: NoUninit + AnyBitPattern>(
input: Rc<A>,
) -> Rc<B> {
try_cast_rc(input).map_err(|(e, _v)| e).unwrap()
}
/// Attempts to cast the content type of a [`Rc`](alloc::rc::Rc).
///
/// On failure you get back an error along with the starting `Rc`.
///
/// The bounds on this function are the same as [`cast_mut`], because a user
/// could call `Rc::get_unchecked_mut` on the output, which could be observable
/// in the input.
///
/// ## Failure
///
/// * The start and end content type of the `Rc` must have the exact same
/// alignment.
/// * The start and end size of the `Rc` must have the exact same size.
#[inline]
pub fn try_cast_rc<A: NoUninit + AnyBitPattern, B: NoUninit + AnyBitPattern>(
input: Rc<A>,
) -> Result<Rc<B>, (PodCastError, Rc<A>)> {
if align_of::<A>() != align_of::<B>() {
Err((PodCastError::AlignmentMismatch, input))
} else if size_of::<A>() != size_of::<B>() {
Err((PodCastError::SizeMismatch, input))
} else {
// Safety: Rc::from_raw requires size and alignment match, which is met.
let ptr: *const B = Rc::into_raw(input) as *const B;
Ok(unsafe { Rc::from_raw(ptr) })
}
}
/// As [`try_cast_arc`](try_cast_arc), but unwraps for you.
#[inline]
#[cfg(target_has_atomic = "ptr")]
pub fn cast_arc<A: NoUninit + AnyBitPattern, B: NoUninit + AnyBitPattern>(
input: Arc<A>,
) -> Arc<B> {
try_cast_arc(input).map_err(|(e, _v)| e).unwrap()
}
/// Attempts to cast the content type of a [`Arc`](alloc::sync::Arc).
///
/// On failure you get back an error along with the starting `Arc`.
///
/// The bounds on this function are the same as [`cast_mut`], because a user
/// could call `Rc::get_unchecked_mut` on the output, which could be observable
/// in the input.
///
/// ## Failure
///
/// * The start and end content type of the `Arc` must have the exact same
/// alignment.
/// * The start and end size of the `Arc` must have the exact same size.
#[inline]
#[cfg(target_has_atomic = "ptr")]
pub fn try_cast_arc<
A: NoUninit + AnyBitPattern,
B: NoUninit + AnyBitPattern,
>(
input: Arc<A>,
) -> Result<Arc<B>, (PodCastError, Arc<A>)> {
if align_of::<A>() != align_of::<B>() {
Err((PodCastError::AlignmentMismatch, input))
} else if size_of::<A>() != size_of::<B>() {
Err((PodCastError::SizeMismatch, input))
} else {
// Safety: Arc::from_raw requires size and alignment match, which is met.
let ptr: *const B = Arc::into_raw(input) as *const B;
Ok(unsafe { Arc::from_raw(ptr) })
}
}
/// As [`try_cast_slice_rc`](try_cast_slice_rc), but unwraps for you.
#[inline]
pub fn cast_slice_rc<
A: NoUninit + AnyBitPattern,
B: NoUninit + AnyBitPattern,
>(
input: Rc<[A]>,
) -> Rc<[B]> {
try_cast_slice_rc(input).map_err(|(e, _v)| e).unwrap()
}
/// Attempts to cast the content type of a `Rc<[T]>`.
///
/// On failure you get back an error along with the starting `Rc<[T]>`.
///
/// The bounds on this function are the same as [`cast_mut`], because a user
/// could call `Rc::get_unchecked_mut` on the output, which could be observable
/// in the input.
///
/// ## Failure
///
/// * The start and end content type of the `Rc<[T]>` must have the exact same
/// alignment.
/// * The start and end content size in bytes of the `Rc<[T]>` must be the exact
/// same.
#[inline]
pub fn try_cast_slice_rc<
A: NoUninit + AnyBitPattern,
B: NoUninit + AnyBitPattern,
>(
input: Rc<[A]>,
) -> Result<Rc<[B]>, (PodCastError, Rc<[A]>)> {
if align_of::<A>() != align_of::<B>() {
Err((PodCastError::AlignmentMismatch, input))
} else if size_of::<A>() != size_of::<B>() {
if size_of::<A>() * input.len() % size_of::<B>() != 0 {
// If the size in bytes of the underlying buffer does not match an exact
// multiple of the size of B, we cannot cast between them.
Err((PodCastError::SizeMismatch, input))
} else {
// Because the size is an exact multiple, we can now change the length
// of the slice and recreate the Rc
// NOTE: This is a valid operation because according to the docs of
// std::rc::Rc::from_raw(), the type U that was in the original Rc<U>
// acquired from Rc::into_raw() must have the same size alignment and
// size of the type T in the new Rc<T>. So as long as both the size
// and alignment stay the same, the Rc will remain a valid Rc.
let length = size_of::<A>() * input.len() / size_of::<B>();
let rc_ptr: *const A = Rc::into_raw(input) as *const A;
// Must use ptr::slice_from_raw_parts, because we cannot make an
// intermediate const reference, because it has mutable provenance,
// nor an intermediate mutable reference, because it could be aliased.
let ptr = core::ptr::slice_from_raw_parts(rc_ptr as *const B, length);
Ok(unsafe { Rc::<[B]>::from_raw(ptr) })
}
} else {
let rc_ptr: *const [A] = Rc::into_raw(input);
let ptr: *const [B] = rc_ptr as *const [B];
Ok(unsafe { Rc::<[B]>::from_raw(ptr) })
}
}
/// As [`try_cast_slice_arc`](try_cast_slice_arc), but unwraps for you.
#[inline]
#[cfg(target_has_atomic = "ptr")]
pub fn cast_slice_arc<
A: NoUninit + AnyBitPattern,
B: NoUninit + AnyBitPattern,
>(
input: Arc<[A]>,
) -> Arc<[B]> {
try_cast_slice_arc(input).map_err(|(e, _v)| e).unwrap()
}
/// Attempts to cast the content type of a `Arc<[T]>`.
///
/// On failure you get back an error along with the starting `Arc<[T]>`.
///
/// The bounds on this function are the same as [`cast_mut`], because a user
/// could call `Rc::get_unchecked_mut` on the output, which could be observable
/// in the input.
///
/// ## Failure
///
/// * The start and end content type of the `Arc<[T]>` must have the exact same
/// alignment.
/// * The start and end content size in bytes of the `Arc<[T]>` must be the
/// exact same.
#[inline]
#[cfg(target_has_atomic = "ptr")]
pub fn try_cast_slice_arc<
A: NoUninit + AnyBitPattern,
B: NoUninit + AnyBitPattern,
>(
input: Arc<[A]>,
) -> Result<Arc<[B]>, (PodCastError, Arc<[A]>)> {
if align_of::<A>() != align_of::<B>() {
Err((PodCastError::AlignmentMismatch, input))
} else if size_of::<A>() != size_of::<B>() {
if size_of::<A>() * input.len() % size_of::<B>() != 0 {
// If the size in bytes of the underlying buffer does not match an exact
// multiple of the size of B, we cannot cast between them.
Err((PodCastError::SizeMismatch, input))
} else {
// Because the size is an exact multiple, we can now change the length
// of the slice and recreate the Arc
// NOTE: This is a valid operation because according to the docs of
// std::sync::Arc::from_raw(), the type U that was in the original Arc<U>
// acquired from Arc::into_raw() must have the same size alignment and
// size of the type T in the new Arc<T>. So as long as both the size
// and alignment stay the same, the Arc will remain a valid Arc.
let length = size_of::<A>() * input.len() / size_of::<B>();
let arc_ptr: *const A = Arc::into_raw(input) as *const A;
// Must use ptr::slice_from_raw_parts, because we cannot make an
// intermediate const reference, because it has mutable provenance,
// nor an intermediate mutable reference, because it could be aliased.
let ptr = core::ptr::slice_from_raw_parts(arc_ptr as *const B, length);
Ok(unsafe { Arc::<[B]>::from_raw(ptr) })
}
} else {
let arc_ptr: *const [A] = Arc::into_raw(input);
let ptr: *const [B] = arc_ptr as *const [B];
Ok(unsafe { Arc::<[B]>::from_raw(ptr) })
}
}
/// An extension trait for `TransparentWrapper` and alloc types.
pub trait TransparentWrapperAlloc<Inner: ?Sized>:
TransparentWrapper<Inner>
{
/// Convert a vec of the inner type into a vec of the wrapper type.
fn wrap_vec(s: Vec<Inner>) -> Vec<Self>
where
Self: Sized,
Inner: Sized,
{
let mut s = core::mem::ManuallyDrop::new(s);
let length = s.len();
let capacity = s.capacity();
let ptr = s.as_mut_ptr();
unsafe {
// SAFETY:
// * ptr comes from Vec (and will not be double-dropped)
// * the two types have the identical representation
// * the len and capacity fields are valid
Vec::from_raw_parts(ptr as *mut Self, length, capacity)
}
}
/// Convert a box to the inner type into a box to the wrapper
/// type.
#[inline]
fn wrap_box(s: Box<Inner>) -> Box<Self> {
assert!(size_of::<*mut Inner>() == size_of::<*mut Self>());
unsafe {
// A pointer cast doesn't work here because rustc can't tell that
// the vtables match (because of the `?Sized` restriction relaxation).
// A `transmute` doesn't work because the sizes are unspecified.
//
// SAFETY:
// * The unsafe contract requires that pointers to Inner and Self have
// identical representations
// * Box is guaranteed to have representation identical to a (non-null)
// pointer
// * The pointer comes from a box (and thus satisfies all safety
// requirements of Box)
let inner_ptr: *mut Inner = Box::into_raw(s);
let wrapper_ptr: *mut Self = transmute!(inner_ptr);
Box::from_raw(wrapper_ptr)
}
}
/// Convert an [`Rc`](alloc::rc::Rc) to the inner type into an `Rc` to the
/// wrapper type.
#[inline]
fn wrap_rc(s: Rc<Inner>) -> Rc<Self> {
assert!(size_of::<*mut Inner>() == size_of::<*mut Self>());
unsafe {
// A pointer cast doesn't work here because rustc can't tell that
// the vtables match (because of the `?Sized` restriction relaxation).
// A `transmute` doesn't work because the layout of Rc is unspecified.
//
// SAFETY:
// * The unsafe contract requires that pointers to Inner and Self have
// identical representations, and that the size and alignment of Inner
// and Self are the same, which meets the safety requirements of
// Rc::from_raw
let inner_ptr: *const Inner = Rc::into_raw(s);
let wrapper_ptr: *const Self = transmute!(inner_ptr);
Rc::from_raw(wrapper_ptr)
}
}
/// Convert an [`Arc`](alloc::sync::Arc) to the inner type into an `Arc` to
/// the wrapper type.
#[inline]
#[cfg(target_has_atomic = "ptr")]
fn wrap_arc(s: Arc<Inner>) -> Arc<Self> {
assert!(size_of::<*mut Inner>() == size_of::<*mut Self>());
unsafe {
// A pointer cast doesn't work here because rustc can't tell that
// the vtables match (because of the `?Sized` restriction relaxation).
// A `transmute` doesn't work because the layout of Arc is unspecified.
//
// SAFETY:
// * The unsafe contract requires that pointers to Inner and Self have
// identical representations, and that the size and alignment of Inner
// and Self are the same, which meets the safety requirements of
// Arc::from_raw
let inner_ptr: *const Inner = Arc::into_raw(s);
let wrapper_ptr: *const Self = transmute!(inner_ptr);
Arc::from_raw(wrapper_ptr)
}
}
/// Convert a vec of the wrapper type into a vec of the inner type.
fn peel_vec(s: Vec<Self>) -> Vec<Inner>
where
Self: Sized,
Inner: Sized,
{
let mut s = core::mem::ManuallyDrop::new(s);
let length = s.len();
let capacity = s.capacity();
let ptr = s.as_mut_ptr();
unsafe {
// SAFETY:
// * ptr comes from Vec (and will not be double-dropped)
// * the two types have the identical representation
// * the len and capacity fields are valid
Vec::from_raw_parts(ptr as *mut Inner, length, capacity)
}
}
/// Convert a box to the wrapper type into a box to the inner
/// type.
#[inline]
fn peel_box(s: Box<Self>) -> Box<Inner> {
assert!(size_of::<*mut Inner>() == size_of::<*mut Self>());
unsafe {
// A pointer cast doesn't work here because rustc can't tell that
// the vtables match (because of the `?Sized` restriction relaxation).
// A `transmute` doesn't work because the sizes are unspecified.
//
// SAFETY:
// * The unsafe contract requires that pointers to Inner and Self have
// identical representations
// * Box is guaranteed to have representation identical to a (non-null)
// pointer
// * The pointer comes from a box (and thus satisfies all safety
// requirements of Box)
let wrapper_ptr: *mut Self = Box::into_raw(s);
let inner_ptr: *mut Inner = transmute!(wrapper_ptr);
Box::from_raw(inner_ptr)
}
}
/// Convert an [`Rc`](alloc::rc::Rc) to the wrapper type into an `Rc` to the
/// inner type.
#[inline]
fn peel_rc(s: Rc<Self>) -> Rc<Inner> {
assert!(size_of::<*mut Inner>() == size_of::<*mut Self>());
unsafe {
// A pointer cast doesn't work here because rustc can't tell that
// the vtables match (because of the `?Sized` restriction relaxation).
// A `transmute` doesn't work because the layout of Rc is unspecified.
//
// SAFETY:
// * The unsafe contract requires that pointers to Inner and Self have
// identical representations, and that the size and alignment of Inner
// and Self are the same, which meets the safety requirements of
// Rc::from_raw
let wrapper_ptr: *const Self = Rc::into_raw(s);
let inner_ptr: *const Inner = transmute!(wrapper_ptr);
Rc::from_raw(inner_ptr)
}
}
/// Convert an [`Arc`](alloc::sync::Arc) to the wrapper type into an `Arc` to
/// the inner type.
#[inline]
#[cfg(target_has_atomic = "ptr")]
fn peel_arc(s: Arc<Self>) -> Arc<Inner> {
assert!(size_of::<*mut Inner>() == size_of::<*mut Self>());
unsafe {
// A pointer cast doesn't work here because rustc can't tell that
// the vtables match (because of the `?Sized` restriction relaxation).
// A `transmute` doesn't work because the layout of Arc is unspecified.
//
// SAFETY:
// * The unsafe contract requires that pointers to Inner and Self have
// identical representations, and that the size and alignment of Inner
// and Self are the same, which meets the safety requirements of
// Arc::from_raw
let wrapper_ptr: *const Self = Arc::into_raw(s);
let inner_ptr: *const Inner = transmute!(wrapper_ptr);
Arc::from_raw(inner_ptr)
}
}
}
impl<I: ?Sized, T: ?Sized + TransparentWrapper<I>> TransparentWrapperAlloc<I> for T {}

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use crate::{Pod, Zeroable};
/// Marker trait for "plain old data" types that are valid for any bit pattern.
///
/// The requirements for this is very similar to [`Pod`],
/// except that the type can allow uninit (or padding) bytes.
/// This limits what you can do with a type of this kind, but also broadens the
/// included types to `repr(C)` `struct`s that contain padding as well as
/// `union`s. Notably, you can only cast *immutable* references and *owned*
/// values into [`AnyBitPattern`] types, not *mutable* references.
///
/// [`Pod`] is a subset of [`AnyBitPattern`], meaning that any `T: Pod` is also
/// [`AnyBitPattern`] but any `T: AnyBitPattern` is not necessarily [`Pod`].
///
/// [`AnyBitPattern`] is a subset of [`Zeroable`], meaning that any `T:
/// AnyBitPattern` is also [`Zeroable`], but any `T: Zeroable` is not
/// necessarily [`AnyBitPattern ]
///
/// # Derive
///
/// A `#[derive(AnyBitPattern)]` macro is provided under the `derive` feature
/// flag which will automatically validate the requirements of this trait and
/// implement the trait for you for both structs and enums. This is the
/// recommended method for implementing the trait, however it's also possible to
/// do manually. If you implement it manually, you *must* carefully follow the
/// below safety rules.
///
/// * *NOTE: even `C-style`, fieldless enums are intentionally **excluded** from
/// this trait, since it is **unsound** for an enum to have a discriminant value
/// that is not one of its defined variants.
///
/// # Safety
///
/// Similar to [`Pod`] except we disregard the rule about it must not contain
/// uninit bytes. Still, this is a quite strong guarantee about a type, so *be
/// careful* when implementing it manually.
///
/// * The type must be inhabited (eg: no
/// [Infallible](core::convert::Infallible)).
/// * The type must be valid for any bit pattern of its backing memory.
/// * Structs need to have all fields also be `AnyBitPattern`.
/// * It is disallowed for types to contain pointer types, `Cell`, `UnsafeCell`,
/// atomics, and any other forms of interior mutability.
/// * More precisely: A shared reference to the type must allow reads, and
/// *only* reads. RustBelt's separation logic is based on the notion that a
/// type is allowed to define a sharing predicate, its own invariant that must
/// hold for shared references, and this predicate is the reasoning that allow
/// it to deal with atomic and cells etc. We require the sharing predicate to
/// be trivial and permit only read-only access.
/// * There's probably more, don't mess it up (I mean it).
pub unsafe trait AnyBitPattern:
Zeroable + Sized + Copy + 'static
{
}
unsafe impl<T: Pod> AnyBitPattern for T {}
#[cfg(feature = "zeroable_maybe_uninit")]
#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "zeroable_maybe_uninit")))]
unsafe impl<T> AnyBitPattern for core::mem::MaybeUninit<T> where T: AnyBitPattern
{}

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//! Checked versions of the casting functions exposed in crate root
//! that support [`CheckedBitPattern`] types.
use crate::{
internal::{self, something_went_wrong},
AnyBitPattern, NoUninit,
};
/// A marker trait that allows types that have some invalid bit patterns to be
/// used in places that otherwise require [`AnyBitPattern`] or [`Pod`] types by
/// performing a runtime check on a perticular set of bits. This is particularly
/// useful for types like fieldless ('C-style') enums, [`char`], bool, and
/// structs containing them.
///
/// To do this, we define a `Bits` type which is a type with equivalent layout
/// to `Self` other than the invalid bit patterns which disallow `Self` from
/// being [`AnyBitPattern`]. This `Bits` type must itself implement
/// [`AnyBitPattern`]. Then, we implement a function that checks whether a
/// certain instance of the `Bits` is also a valid bit pattern of `Self`. If
/// this check passes, then we can allow casting from the `Bits` to `Self` (and
/// therefore, any type which is able to be cast to `Bits` is also able to be
/// cast to `Self`).
///
/// [`AnyBitPattern`] is a subset of [`CheckedBitPattern`], meaning that any `T:
/// AnyBitPattern` is also [`CheckedBitPattern`]. This means you can also use
/// any [`AnyBitPattern`] type in the checked versions of casting functions in
/// this module. If it's possible, prefer implementing [`AnyBitPattern`] for
/// your type directly instead of [`CheckedBitPattern`] as it gives greater
/// flexibility.
///
/// # Derive
///
/// A `#[derive(CheckedBitPattern)]` macro is provided under the `derive`
/// feature flag which will automatically validate the requirements of this
/// trait and implement the trait for you for both enums and structs. This is
/// the recommended method for implementing the trait, however it's also
/// possible to do manually.
///
/// # Example
///
/// If manually implementing the trait, we can do something like so:
///
/// ```rust
/// use bytemuck::{CheckedBitPattern, NoUninit};
///
/// #[repr(u32)]
/// #[derive(Copy, Clone)]
/// enum MyEnum {
/// Variant0 = 0,
/// Variant1 = 1,
/// Variant2 = 2,
/// }
///
/// unsafe impl CheckedBitPattern for MyEnum {
/// type Bits = u32;
///
/// fn is_valid_bit_pattern(bits: &u32) -> bool {
/// match *bits {
/// 0 | 1 | 2 => true,
/// _ => false,
/// }
/// }
/// }
///
/// // It is often useful to also implement `NoUninit` on our `CheckedBitPattern` types.
/// // This will allow us to do casting of mutable references (and mutable slices).
/// // It is not always possible to do so, but in this case we have no padding so it is.
/// unsafe impl NoUninit for MyEnum {}
/// ```
///
/// We can now use relevant casting functions. For example,
///
/// ```rust
/// # use bytemuck::{CheckedBitPattern, NoUninit};
/// # #[repr(u32)]
/// # #[derive(Copy, Clone, PartialEq, Eq, Debug)]
/// # enum MyEnum {
/// # Variant0 = 0,
/// # Variant1 = 1,
/// # Variant2 = 2,
/// # }
/// # unsafe impl NoUninit for MyEnum {}
/// # unsafe impl CheckedBitPattern for MyEnum {
/// # type Bits = u32;
/// # fn is_valid_bit_pattern(bits: &u32) -> bool {
/// # match *bits {
/// # 0 | 1 | 2 => true,
/// # _ => false,
/// # }
/// # }
/// # }
/// use bytemuck::{bytes_of, bytes_of_mut};
/// use bytemuck::checked;
///
/// let bytes = bytes_of(&2u32);
/// let result = checked::try_from_bytes::<MyEnum>(bytes);
/// assert_eq!(result, Ok(&MyEnum::Variant2));
///
/// // Fails for invalid discriminant
/// let bytes = bytes_of(&100u32);
/// let result = checked::try_from_bytes::<MyEnum>(bytes);
/// assert!(result.is_err());
///
/// // Since we implemented NoUninit, we can also cast mutably from an original type
/// // that is `NoUninit + AnyBitPattern`:
/// let mut my_u32 = 2u32;
/// {
/// let as_enum_mut = checked::cast_mut::<_, MyEnum>(&mut my_u32);
/// assert_eq!(as_enum_mut, &mut MyEnum::Variant2);
/// *as_enum_mut = MyEnum::Variant0;
/// }
/// assert_eq!(my_u32, 0u32);
/// ```
///
/// # Safety
///
/// * `Self` *must* have the same layout as the specified `Bits` except for
/// the possible invalid bit patterns being checked during
/// [`is_valid_bit_pattern`].
/// * This almost certainly means your type must be `#[repr(C)]` or a similar
/// specified repr, but if you think you know better, you probably don't. If
/// you still think you know better, be careful and have fun. And don't mess
/// it up (I mean it).
/// * If [`is_valid_bit_pattern`] returns true, then the bit pattern contained
/// in `bits` must also be valid for an instance of `Self`.
/// * Probably more, don't mess it up (I mean it 2.0)
///
/// [`is_valid_bit_pattern`]: CheckedBitPattern::is_valid_bit_pattern
/// [`Pod`]: crate::Pod
pub unsafe trait CheckedBitPattern: Copy {
/// `Self` *must* have the same layout as the specified `Bits` except for
/// the possible invalid bit patterns being checked during
/// [`is_valid_bit_pattern`].
///
/// [`is_valid_bit_pattern`]: CheckedBitPattern::is_valid_bit_pattern
type Bits: AnyBitPattern;
/// If this function returns true, then it must be valid to reinterpret `bits`
/// as `&Self`.
fn is_valid_bit_pattern(bits: &Self::Bits) -> bool;
}
unsafe impl<T: AnyBitPattern> CheckedBitPattern for T {
type Bits = T;
#[inline(always)]
fn is_valid_bit_pattern(_bits: &T) -> bool {
true
}
}
unsafe impl CheckedBitPattern for char {
type Bits = u32;
#[inline]
fn is_valid_bit_pattern(bits: &Self::Bits) -> bool {
core::char::from_u32(*bits).is_some()
}
}
unsafe impl CheckedBitPattern for bool {
type Bits = u8;
#[inline]
fn is_valid_bit_pattern(bits: &Self::Bits) -> bool {
match *bits {
0 | 1 => true,
_ => false,
}
}
}
// Rust 1.70.0 documents that NonZero[int] has the same layout as [int].
macro_rules! impl_checked_for_nonzero {
($($nonzero:ty: $primitive:ty),* $(,)?) => {
$(
unsafe impl CheckedBitPattern for $nonzero {
type Bits = $primitive;
#[inline]
fn is_valid_bit_pattern(bits: &Self::Bits) -> bool {
*bits != 0
}
}
)*
};
}
impl_checked_for_nonzero! {
core::num::NonZeroU8: u8,
core::num::NonZeroI8: i8,
core::num::NonZeroU16: u16,
core::num::NonZeroI16: i16,
core::num::NonZeroU32: u32,
core::num::NonZeroI32: i32,
core::num::NonZeroU64: u64,
core::num::NonZeroI64: i64,
core::num::NonZeroI128: i128,
core::num::NonZeroU128: u128,
core::num::NonZeroUsize: usize,
core::num::NonZeroIsize: isize,
}
/// The things that can go wrong when casting between [`CheckedBitPattern`] data
/// forms.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum CheckedCastError {
/// An error occurred during a true-[`Pod`] cast
///
/// [`Pod`]: crate::Pod
PodCastError(crate::PodCastError),
/// When casting to a [`CheckedBitPattern`] type, it is possible that the
/// original data contains an invalid bit pattern. If so, the cast will
/// fail and this error will be returned. Will never happen on casts
/// between [`Pod`] types.
///
/// [`Pod`]: crate::Pod
InvalidBitPattern,
}
#[cfg(not(target_arch = "spirv"))]
impl core::fmt::Display for CheckedCastError {
fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
write!(f, "{:?}", self)
}
}
#[cfg(feature = "extern_crate_std")]
#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "extern_crate_std")))]
impl std::error::Error for CheckedCastError {}
impl From<crate::PodCastError> for CheckedCastError {
fn from(err: crate::PodCastError) -> CheckedCastError {
CheckedCastError::PodCastError(err)
}
}
/// Re-interprets `&[u8]` as `&T`.
///
/// ## Failure
///
/// * If the slice isn't aligned for the new type
/// * If the slice's length isn’t exactly the size of the new type
/// * If the slice contains an invalid bit pattern for `T`
#[inline]
pub fn try_from_bytes<T: CheckedBitPattern>(
s: &[u8],
) -> Result<&T, CheckedCastError> {
let pod = crate::try_from_bytes(s)?;
if <T as CheckedBitPattern>::is_valid_bit_pattern(pod) {
Ok(unsafe { &*(pod as *const <T as CheckedBitPattern>::Bits as *const T) })
} else {
Err(CheckedCastError::InvalidBitPattern)
}
}
/// Re-interprets `&mut [u8]` as `&mut T`.
///
/// ## Failure
///
/// * If the slice isn't aligned for the new type
/// * If the slice's length isn’t exactly the size of the new type
/// * If the slice contains an invalid bit pattern for `T`
#[inline]
pub fn try_from_bytes_mut<T: CheckedBitPattern + NoUninit>(
s: &mut [u8],
) -> Result<&mut T, CheckedCastError> {
let pod = unsafe { internal::try_from_bytes_mut(s) }?;
if <T as CheckedBitPattern>::is_valid_bit_pattern(pod) {
Ok(unsafe { &mut *(pod as *mut <T as CheckedBitPattern>::Bits as *mut T) })
} else {
Err(CheckedCastError::InvalidBitPattern)
}
}
/// Reads from the bytes as if they were a `T`.
///
/// ## Failure
/// * If the `bytes` length is not equal to `size_of::<T>()`.
/// * If the slice contains an invalid bit pattern for `T`
#[inline]
pub fn try_pod_read_unaligned<T: CheckedBitPattern>(
bytes: &[u8],
) -> Result<T, CheckedCastError> {
let pod = crate::try_pod_read_unaligned(bytes)?;
if <T as CheckedBitPattern>::is_valid_bit_pattern(&pod) {
Ok(unsafe { transmute!(pod) })
} else {
Err(CheckedCastError::InvalidBitPattern)
}
}
/// Try to cast `T` into `U`.
///
/// Note that for this particular type of cast, alignment isn't a factor. The
/// input value is semantically copied into the function and then returned to a
/// new memory location which will have whatever the required alignment of the
/// output type is.
///
/// ## Failure
///
/// * If the types don't have the same size this fails.
/// * If `a` contains an invalid bit pattern for `B` this fails.
#[inline]
pub fn try_cast<A: NoUninit, B: CheckedBitPattern>(
a: A,
) -> Result<B, CheckedCastError> {
let pod = crate::try_cast(a)?;
if <B as CheckedBitPattern>::is_valid_bit_pattern(&pod) {
Ok(unsafe { transmute!(pod) })
} else {
Err(CheckedCastError::InvalidBitPattern)
}
}
/// Try to convert a `&T` into `&U`.
///
/// ## Failure
///
/// * If the reference isn't aligned in the new type
/// * If the source type and target type aren't the same size.
/// * If `a` contains an invalid bit pattern for `B` this fails.
#[inline]
pub fn try_cast_ref<A: NoUninit, B: CheckedBitPattern>(
a: &A,
) -> Result<&B, CheckedCastError> {
let pod = crate::try_cast_ref(a)?;
if <B as CheckedBitPattern>::is_valid_bit_pattern(pod) {
Ok(unsafe { &*(pod as *const <B as CheckedBitPattern>::Bits as *const B) })
} else {
Err(CheckedCastError::InvalidBitPattern)
}
}
/// Try to convert a `&mut T` into `&mut U`.
///
/// As [`try_cast_ref`], but `mut`.
#[inline]
pub fn try_cast_mut<
A: NoUninit + AnyBitPattern,
B: CheckedBitPattern + NoUninit,
>(
a: &mut A,
) -> Result<&mut B, CheckedCastError> {
let pod = unsafe { internal::try_cast_mut(a) }?;
if <B as CheckedBitPattern>::is_valid_bit_pattern(pod) {
Ok(unsafe { &mut *(pod as *mut <B as CheckedBitPattern>::Bits as *mut B) })
} else {
Err(CheckedCastError::InvalidBitPattern)
}
}
/// Try to convert `&[A]` into `&[B]` (possibly with a change in length).
///
/// * `input.as_ptr() as usize == output.as_ptr() as usize`
/// * `input.len() * size_of::<A>() == output.len() * size_of::<B>()`
///
/// ## Failure
///
/// * If the target type has a greater alignment requirement and the input slice
/// isn't aligned.
/// * If the target element type is a different size from the current element
/// type, and the output slice wouldn't be a whole number of elements when
/// accounting for the size change (eg: 3 `u16` values is 1.5 `u32` values, so
/// that's a failure).
/// * Similarly, you can't convert between a [ZST](https://doc.rust-lang.org/nomicon/exotic-sizes.html#zero-sized-types-zsts)
/// and a non-ZST.
/// * If any element of the converted slice would contain an invalid bit pattern
/// for `B` this fails.
#[inline]
pub fn try_cast_slice<A: NoUninit, B: CheckedBitPattern>(
a: &[A],
) -> Result<&[B], CheckedCastError> {
let pod = crate::try_cast_slice(a)?;
if pod.iter().all(|pod| <B as CheckedBitPattern>::is_valid_bit_pattern(pod)) {
Ok(unsafe {
core::slice::from_raw_parts(pod.as_ptr() as *const B, pod.len())
})
} else {
Err(CheckedCastError::InvalidBitPattern)
}
}
/// Try to convert `&mut [A]` into `&mut [B]` (possibly with a change in
/// length).
///
/// As [`try_cast_slice`], but `&mut`.
#[inline]
pub fn try_cast_slice_mut<
A: NoUninit + AnyBitPattern,
B: CheckedBitPattern + NoUninit,
>(
a: &mut [A],
) -> Result<&mut [B], CheckedCastError> {
let pod = unsafe { internal::try_cast_slice_mut(a) }?;
if pod.iter().all(|pod| <B as CheckedBitPattern>::is_valid_bit_pattern(pod)) {
Ok(unsafe {
core::slice::from_raw_parts_mut(pod.as_mut_ptr() as *mut B, pod.len())
})
} else {
Err(CheckedCastError::InvalidBitPattern)
}
}
/// Re-interprets `&[u8]` as `&T`.
///
/// ## Panics
///
/// This is [`try_from_bytes`] but will panic on error.
#[inline]
pub fn from_bytes<T: CheckedBitPattern>(s: &[u8]) -> &T {
match try_from_bytes(s) {
Ok(t) => t,
Err(e) => something_went_wrong("from_bytes", e),
}
}
/// Re-interprets `&mut [u8]` as `&mut T`.
///
/// ## Panics
///
/// This is [`try_from_bytes_mut`] but will panic on error.
#[inline]
pub fn from_bytes_mut<T: NoUninit + CheckedBitPattern>(s: &mut [u8]) -> &mut T {
match try_from_bytes_mut(s) {
Ok(t) => t,
Err(e) => something_went_wrong("from_bytes_mut", e),
}
}
/// Reads the slice into a `T` value.
///
/// ## Panics
/// * This is like `try_pod_read_unaligned` but will panic on failure.
#[inline]
pub fn pod_read_unaligned<T: CheckedBitPattern>(bytes: &[u8]) -> T {
match try_pod_read_unaligned(bytes) {
Ok(t) => t,
Err(e) => something_went_wrong("pod_read_unaligned", e),
}
}
/// Cast `T` into `U`
///
/// ## Panics
///
/// * This is like [`try_cast`](try_cast), but will panic on a size mismatch.
#[inline]
pub fn cast<A: NoUninit, B: CheckedBitPattern>(a: A) -> B {
match try_cast(a) {
Ok(t) => t,
Err(e) => something_went_wrong("cast", e),
}
}
/// Cast `&mut T` into `&mut U`.
///
/// ## Panics
///
/// This is [`try_cast_mut`] but will panic on error.
#[inline]
pub fn cast_mut<
A: NoUninit + AnyBitPattern,
B: NoUninit + CheckedBitPattern,
>(
a: &mut A,
) -> &mut B {
match try_cast_mut(a) {
Ok(t) => t,
Err(e) => something_went_wrong("cast_mut", e),
}
}
/// Cast `&T` into `&U`.
///
/// ## Panics
///
/// This is [`try_cast_ref`] but will panic on error.
#[inline]
pub fn cast_ref<A: NoUninit, B: CheckedBitPattern>(a: &A) -> &B {
match try_cast_ref(a) {
Ok(t) => t,
Err(e) => something_went_wrong("cast_ref", e),
}
}
/// Cast `&[A]` into `&[B]`.
///
/// ## Panics
///
/// This is [`try_cast_slice`] but will panic on error.
#[inline]
pub fn cast_slice<A: NoUninit, B: CheckedBitPattern>(a: &[A]) -> &[B] {
match try_cast_slice(a) {
Ok(t) => t,
Err(e) => something_went_wrong("cast_slice", e),
}
}
/// Cast `&mut [T]` into `&mut [U]`.
///
/// ## Panics
///
/// This is [`try_cast_slice_mut`] but will panic on error.
#[inline]
pub fn cast_slice_mut<
A: NoUninit + AnyBitPattern,
B: NoUninit + CheckedBitPattern,
>(
a: &mut [A],
) -> &mut [B] {
match try_cast_slice_mut(a) {
Ok(t) => t,
Err(e) => something_went_wrong("cast_slice_mut", e),
}
}

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use super::*;
/// A trait indicating that:
///
/// 1. A type has an equivalent representation to some known integral type.
/// 2. All instances of this type fall in a fixed range of values.
/// 3. Within that range, there are no gaps.
///
/// This is generally useful for fieldless enums (aka "c-style" enums), however
/// it's important that it only be used for those with an explicit `#[repr]`, as
/// `#[repr(Rust)]` fieldess enums have an unspecified layout.
///
/// Additionally, you shouldn't assume that all implementations are enums. Any
/// type which meets the requirements above while following the rules under
/// "Safety" below is valid.
///
/// # Example
///
/// ```
/// # use bytemuck::Contiguous;
/// #[repr(u8)]
/// #[derive(Debug, Copy, Clone, PartialEq)]
/// enum Foo {
/// A = 0,
/// B = 1,
/// C = 2,
/// D = 3,
/// E = 4,
/// }
/// unsafe impl Contiguous for Foo {
/// type Int = u8;
/// const MIN_VALUE: u8 = Foo::A as u8;
/// const MAX_VALUE: u8 = Foo::E as u8;
/// }
/// assert_eq!(Foo::from_integer(3).unwrap(), Foo::D);
/// assert_eq!(Foo::from_integer(8), None);
/// assert_eq!(Foo::C.into_integer(), 2);
/// ```
/// # Safety
///
/// This is an unsafe trait, and incorrectly implementing it is undefined
/// behavior.
///
/// Informally, by implementing it, you're asserting that `C` is identical to
/// the integral type `C::Int`, and that every `C` falls between `C::MIN_VALUE`
/// and `C::MAX_VALUE` exactly once, without any gaps.
///
/// Precisely, the guarantees you must uphold when implementing `Contiguous` for
/// some type `C` are:
///
/// 1. The size of `C` and `C::Int` must be the same, and neither may be a ZST.
/// (Note: alignment is explicitly allowed to differ)
///
/// 2. `C::Int` must be a primitive integer, and not a wrapper type. In the
/// future, this may be lifted to include cases where the behavior is
/// identical for a relevant set of traits (Ord, arithmetic, ...).
///
/// 3. All `C::Int`s which are in the *inclusive* range between `C::MIN_VALUE`
/// and `C::MAX_VALUE` are bitwise identical to unique valid instances of
/// `C`.
///
/// 4. There exist no instances of `C` such that their bitpatterns, when
/// interpreted as instances of `C::Int`, fall outside of the `MAX_VALUE` /
/// `MIN_VALUE` range -- It is legal for unsafe code to assume that if it
/// gets a `C` that implements `Contiguous`, it is in the appropriate range.
///
/// 5. Finally, you promise not to provide overridden implementations of
/// `Contiguous::from_integer` and `Contiguous::into_integer`.
///
/// For clarity, the following rules could be derived from the above, but are
/// listed explicitly:
///
/// - `C::MAX_VALUE` must be greater or equal to `C::MIN_VALUE` (therefore, `C`
/// must be an inhabited type).
///
/// - There exist no two values between `MIN_VALUE` and `MAX_VALUE` such that
/// when interpreted as a `C` they are considered identical (by, say, match).
pub unsafe trait Contiguous: Copy + 'static {
/// The primitive integer type with an identical representation to this
/// type.
///
/// Contiguous is broadly intended for use with fieldless enums, and for
/// these the correct integer type is easy: The enum should have a
/// `#[repr(Int)]` or `#[repr(C)]` attribute, (if it does not, it is
/// *unsound* to implement `Contiguous`!).
///
/// - For `#[repr(Int)]`, use the listed `Int`. e.g. `#[repr(u8)]` should use
/// `type Int = u8`.
///
/// - For `#[repr(C)]`, use whichever type the C compiler will use to
/// represent the given enum. This is usually `c_int` (from `std::os::raw`
/// or `libc`), but it's up to you to make the determination as the
/// implementer of the unsafe trait.
///
/// For precise rules, see the list under "Safety" above.
type Int: Copy + Ord;
/// The upper *inclusive* bound for valid instances of this type.
const MAX_VALUE: Self::Int;
/// The lower *inclusive* bound for valid instances of this type.
const MIN_VALUE: Self::Int;
/// If `value` is within the range for valid instances of this type,
/// returns `Some(converted_value)`, otherwise, returns `None`.
///
/// This is a trait method so that you can write `value.into_integer()` in
/// your code. It is a contract of this trait that if you implement
/// `Contiguous` on your type you **must not** override this method.
///
/// # Panics
///
/// We will not panic for any correct implementation of `Contiguous`, but
/// *may* panic if we detect an incorrect one.
///
/// This is undefined behavior regardless, so it could have been the nasal
/// demons at that point anyway ;).
#[inline]
fn from_integer(value: Self::Int) -> Option<Self> {
// Guard against an illegal implementation of Contiguous. Annoyingly we
// can't rely on `transmute` to do this for us (see below), but
// whatever, this gets compiled into nothing in release.
assert!(size_of::<Self>() == size_of::<Self::Int>());
if Self::MIN_VALUE <= value && value <= Self::MAX_VALUE {
// SAFETY: We've checked their bounds (and their size, even though
// they've sworn under the Oath Of Unsafe Rust that that already
// matched) so this is allowed by `Contiguous`'s unsafe contract.
//
// So, the `transmute!`. ideally we'd use transmute here, which
// is more obviously safe. Sadly, we can't, as these types still
// have unspecified sizes.
Some(unsafe { transmute!(value) })
} else {
None
}
}
/// Perform the conversion from `C` into the underlying integral type. This
/// mostly exists otherwise generic code would need unsafe for the `value as
/// integer`
///
/// This is a trait method so that you can write `value.into_integer()` in
/// your code. It is a contract of this trait that if you implement
/// `Contiguous` on your type you **must not** override this method.
///
/// # Panics
///
/// We will not panic for any correct implementation of `Contiguous`, but
/// *may* panic if we detect an incorrect one.
///
/// This is undefined behavior regardless, so it could have been the nasal
/// demons at that point anyway ;).
#[inline]
fn into_integer(self) -> Self::Int {
// Guard against an illegal implementation of Contiguous. Annoyingly we
// can't rely on `transmute` to do the size check for us (see
// `from_integer's comment`), but whatever, this gets compiled into
// nothing in release. Note that we don't check the result of cast
assert!(size_of::<Self>() == size_of::<Self::Int>());
// SAFETY: The unsafe contract requires that these have identical
// representations, and that the range be entirely valid. Using
// transmute! instead of transmute here is annoying, but is required
// as `Self` and `Self::Int` have unspecified sizes still.
unsafe { transmute!(self) }
}
}
macro_rules! impl_contiguous {
($($src:ty as $repr:ident in [$min:expr, $max:expr];)*) => {$(
unsafe impl Contiguous for $src {
type Int = $repr;
const MAX_VALUE: $repr = $max;
const MIN_VALUE: $repr = $min;
}
)*};
}
impl_contiguous! {
bool as u8 in [0, 1];
u8 as u8 in [0, u8::max_value()];
u16 as u16 in [0, u16::max_value()];
u32 as u32 in [0, u32::max_value()];
u64 as u64 in [0, u64::max_value()];
u128 as u128 in [0, u128::max_value()];
usize as usize in [0, usize::max_value()];
i8 as i8 in [i8::min_value(), i8::max_value()];
i16 as i16 in [i16::min_value(), i16::max_value()];
i32 as i32 in [i32::min_value(), i32::max_value()];
i64 as i64 in [i64::min_value(), i64::max_value()];
i128 as i128 in [i128::min_value(), i128::max_value()];
isize as isize in [isize::min_value(), isize::max_value()];
NonZeroU8 as u8 in [1, u8::max_value()];
NonZeroU16 as u16 in [1, u16::max_value()];
NonZeroU32 as u32 in [1, u32::max_value()];
NonZeroU64 as u64 in [1, u64::max_value()];
NonZeroU128 as u128 in [1, u128::max_value()];
NonZeroUsize as usize in [1, usize::max_value()];
}

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//! Internal implementation of casting functions not bound by marker traits
//! and therefore marked as unsafe. This is used so that we don't need to
//! duplicate the business logic contained in these functions between the
//! versions exported in the crate root, `checked`, and `relaxed` modules.
#![allow(unused_unsafe)]
use crate::PodCastError;
use core::{marker::*, mem::*};
/*
Note(Lokathor): We've switched all of the `unwrap` to `match` because there is
apparently a bug: https://github.com/rust-lang/rust/issues/68667
and it doesn't seem to show up in simple godbolt examples but has been reported
as having an impact when there's a cast mixed in with other more complicated
code around it. Rustc/LLVM ends up missing that the `Err` can't ever happen for
particular type combinations, and then it doesn't fully eliminated the panic
possibility code branch.
*/
/// Immediately panics.
#[cfg(not(target_arch = "spirv"))]
#[cold]
#[inline(never)]
pub(crate) fn something_went_wrong<D: core::fmt::Display>(
_src: &str, _err: D,
) -> ! {
// Note(Lokathor): Keeping the panic here makes the panic _formatting_ go
// here too, which helps assembly readability and also helps keep down
// the inline pressure.
panic!("{src}>{err}", src = _src, err = _err);
}
/// Immediately panics.
#[cfg(target_arch = "spirv")]
#[cold]
#[inline(never)]
pub(crate) fn something_went_wrong<D>(_src: &str, _err: D) -> ! {
// Note: On the spirv targets from [rust-gpu](https://github.com/EmbarkStudios/rust-gpu)
// panic formatting cannot be used. We we just give a generic error message
// The chance that the panicking version of these functions will ever get
// called on spir-v targets with invalid inputs is small, but giving a
// simple error message is better than no error message at all.
panic!("Called a panicing helper from bytemuck which paniced");
}
/// Re-interprets `&T` as `&[u8]`.
///
/// Any ZST becomes an empty slice, and in that case the pointer value of that
/// empty slice might not match the pointer value of the input reference.
#[inline(always)]
pub(crate) unsafe fn bytes_of<T: Copy>(t: &T) -> &[u8] {
if size_of::<T>() == 0 {
&[]
} else {
match try_cast_slice::<T, u8>(core::slice::from_ref(t)) {
Ok(s) => s,
Err(_) => unreachable!(),
}
}
}
/// Re-interprets `&mut T` as `&mut [u8]`.
///
/// Any ZST becomes an empty slice, and in that case the pointer value of that
/// empty slice might not match the pointer value of the input reference.
#[inline]
pub(crate) unsafe fn bytes_of_mut<T: Copy>(t: &mut T) -> &mut [u8] {
if size_of::<T>() == 0 {
&mut []
} else {
match try_cast_slice_mut::<T, u8>(core::slice::from_mut(t)) {
Ok(s) => s,
Err(_) => unreachable!(),
}
}
}
/// Re-interprets `&[u8]` as `&T`.
///
/// ## Panics
///
/// This is [`try_from_bytes`] but will panic on error.
#[inline]
pub(crate) unsafe fn from_bytes<T: Copy>(s: &[u8]) -> &T {
match try_from_bytes(s) {
Ok(t) => t,
Err(e) => something_went_wrong("from_bytes", e),
}
}
/// Re-interprets `&mut [u8]` as `&mut T`.
///
/// ## Panics
///
/// This is [`try_from_bytes_mut`] but will panic on error.
#[inline]
pub(crate) unsafe fn from_bytes_mut<T: Copy>(s: &mut [u8]) -> &mut T {
match try_from_bytes_mut(s) {
Ok(t) => t,
Err(e) => something_went_wrong("from_bytes_mut", e),
}
}
/// Reads from the bytes as if they were a `T`.
///
/// ## Failure
/// * If the `bytes` length is not equal to `size_of::<T>()`.
#[inline]
pub(crate) unsafe fn try_pod_read_unaligned<T: Copy>(
bytes: &[u8],
) -> Result<T, PodCastError> {
if bytes.len() != size_of::<T>() {
Err(PodCastError::SizeMismatch)
} else {
Ok(unsafe { (bytes.as_ptr() as *const T).read_unaligned() })
}
}
/// Reads the slice into a `T` value.
///
/// ## Panics
/// * This is like `try_pod_read_unaligned` but will panic on failure.
#[inline]
pub(crate) unsafe fn pod_read_unaligned<T: Copy>(bytes: &[u8]) -> T {
match try_pod_read_unaligned(bytes) {
Ok(t) => t,
Err(e) => something_went_wrong("pod_read_unaligned", e),
}
}
/// Checks if `ptr` is aligned to an `align` memory boundary.
///
/// ## Panics
/// * If `align` is not a power of two. This includes when `align` is zero.
#[inline]
pub(crate) fn is_aligned_to(ptr: *const (), align: usize) -> bool {
#[cfg(feature = "align_offset")]
{
// This is in a way better than `ptr as usize % align == 0`,
// because casting a pointer to an integer has the side effect that it
// exposes the pointer's provenance, which may theoretically inhibit
// some compiler optimizations.
ptr.align_offset(align) == 0
}
#[cfg(not(feature = "align_offset"))]
{
((ptr as usize) % align) == 0
}
}
/// Re-interprets `&[u8]` as `&T`.
///
/// ## Failure
///
/// * If the slice isn't aligned for the new type
/// * If the slice's length isn’t exactly the size of the new type
#[inline]
pub(crate) unsafe fn try_from_bytes<T: Copy>(
s: &[u8],
) -> Result<&T, PodCastError> {
if s.len() != size_of::<T>() {
Err(PodCastError::SizeMismatch)
} else if !is_aligned_to(s.as_ptr() as *const (), align_of::<T>()) {
Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
} else {
Ok(unsafe { &*(s.as_ptr() as *const T) })
}
}
/// Re-interprets `&mut [u8]` as `&mut T`.
///
/// ## Failure
///
/// * If the slice isn't aligned for the new type
/// * If the slice's length isn’t exactly the size of the new type
#[inline]
pub(crate) unsafe fn try_from_bytes_mut<T: Copy>(
s: &mut [u8],
) -> Result<&mut T, PodCastError> {
if s.len() != size_of::<T>() {
Err(PodCastError::SizeMismatch)
} else if !is_aligned_to(s.as_ptr() as *const (), align_of::<T>()) {
Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
} else {
Ok(unsafe { &mut *(s.as_mut_ptr() as *mut T) })
}
}
/// Cast `T` into `U`
///
/// ## Panics
///
/// * This is like [`try_cast`](try_cast), but will panic on a size mismatch.
#[inline]
pub(crate) unsafe fn cast<A: Copy, B: Copy>(a: A) -> B {
if size_of::<A>() == size_of::<B>() {
unsafe { transmute!(a) }
} else {
something_went_wrong("cast", PodCastError::SizeMismatch)
}
}
/// Cast `&mut T` into `&mut U`.
///
/// ## Panics
///
/// This is [`try_cast_mut`] but will panic on error.
#[inline]
pub(crate) unsafe fn cast_mut<A: Copy, B: Copy>(a: &mut A) -> &mut B {
if size_of::<A>() == size_of::<B>() && align_of::<A>() >= align_of::<B>() {
// Plz mr compiler, just notice that we can't ever hit Err in this case.
match try_cast_mut(a) {
Ok(b) => b,
Err(_) => unreachable!(),
}
} else {
match try_cast_mut(a) {
Ok(b) => b,
Err(e) => something_went_wrong("cast_mut", e),
}
}
}
/// Cast `&T` into `&U`.
///
/// ## Panics
///
/// This is [`try_cast_ref`] but will panic on error.
#[inline]
pub(crate) unsafe fn cast_ref<A: Copy, B: Copy>(a: &A) -> &B {
if size_of::<A>() == size_of::<B>() && align_of::<A>() >= align_of::<B>() {
// Plz mr compiler, just notice that we can't ever hit Err in this case.
match try_cast_ref(a) {
Ok(b) => b,
Err(_) => unreachable!(),
}
} else {
match try_cast_ref(a) {
Ok(b) => b,
Err(e) => something_went_wrong("cast_ref", e),
}
}
}
/// Cast `&[A]` into `&[B]`.
///
/// ## Panics
///
/// This is [`try_cast_slice`] but will panic on error.
#[inline]
pub(crate) unsafe fn cast_slice<A: Copy, B: Copy>(a: &[A]) -> &[B] {
match try_cast_slice(a) {
Ok(b) => b,
Err(e) => something_went_wrong("cast_slice", e),
}
}
/// Cast `&mut [T]` into `&mut [U]`.
///
/// ## Panics
///
/// This is [`try_cast_slice_mut`] but will panic on error.
#[inline]
pub(crate) unsafe fn cast_slice_mut<A: Copy, B: Copy>(a: &mut [A]) -> &mut [B] {
match try_cast_slice_mut(a) {
Ok(b) => b,
Err(e) => something_went_wrong("cast_slice_mut", e),
}
}
/// Try to cast `T` into `U`.
///
/// Note that for this particular type of cast, alignment isn't a factor. The
/// input value is semantically copied into the function and then returned to a
/// new memory location which will have whatever the required alignment of the
/// output type is.
///
/// ## Failure
///
/// * If the types don't have the same size this fails.
#[inline]
pub(crate) unsafe fn try_cast<A: Copy, B: Copy>(
a: A,
) -> Result<B, PodCastError> {
if size_of::<A>() == size_of::<B>() {
Ok(unsafe { transmute!(a) })
} else {
Err(PodCastError::SizeMismatch)
}
}
/// Try to convert a `&T` into `&U`.
///
/// ## Failure
///
/// * If the reference isn't aligned in the new type
/// * If the source type and target type aren't the same size.
#[inline]
pub(crate) unsafe fn try_cast_ref<A: Copy, B: Copy>(
a: &A,
) -> Result<&B, PodCastError> {
// Note(Lokathor): everything with `align_of` and `size_of` will optimize away
// after monomorphization.
if align_of::<B>() > align_of::<A>()
&& !is_aligned_to(a as *const A as *const (), align_of::<B>())
{
Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
} else if size_of::<B>() == size_of::<A>() {
Ok(unsafe { &*(a as *const A as *const B) })
} else {
Err(PodCastError::SizeMismatch)
}
}
/// Try to convert a `&mut T` into `&mut U`.
///
/// As [`try_cast_ref`], but `mut`.
#[inline]
pub(crate) unsafe fn try_cast_mut<A: Copy, B: Copy>(
a: &mut A,
) -> Result<&mut B, PodCastError> {
// Note(Lokathor): everything with `align_of` and `size_of` will optimize away
// after monomorphization.
if align_of::<B>() > align_of::<A>()
&& !is_aligned_to(a as *const A as *const (), align_of::<B>())
{
Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
} else if size_of::<B>() == size_of::<A>() {
Ok(unsafe { &mut *(a as *mut A as *mut B) })
} else {
Err(PodCastError::SizeMismatch)
}
}
/// Try to convert `&[A]` into `&[B]` (possibly with a change in length).
///
/// * `input.as_ptr() as usize == output.as_ptr() as usize`
/// * `input.len() * size_of::<A>() == output.len() * size_of::<B>()`
///
/// ## Failure
///
/// * If the target type has a greater alignment requirement and the input slice
/// isn't aligned.
/// * If the target element type is a different size from the current element
/// type, and the output slice wouldn't be a whole number of elements when
/// accounting for the size change (eg: 3 `u16` values is 1.5 `u32` values, so
/// that's a failure).
/// * Similarly, you can't convert between a [ZST](https://doc.rust-lang.org/nomicon/exotic-sizes.html#zero-sized-types-zsts)
/// and a non-ZST.
#[inline]
pub(crate) unsafe fn try_cast_slice<A: Copy, B: Copy>(
a: &[A],
) -> Result<&[B], PodCastError> {
// Note(Lokathor): everything with `align_of` and `size_of` will optimize away
// after monomorphization.
if align_of::<B>() > align_of::<A>()
&& !is_aligned_to(a.as_ptr() as *const (), align_of::<B>())
{
Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
} else if size_of::<B>() == size_of::<A>() {
Ok(unsafe { core::slice::from_raw_parts(a.as_ptr() as *const B, a.len()) })
} else if size_of::<A>() == 0 || size_of::<B>() == 0 {
Err(PodCastError::SizeMismatch)
} else if core::mem::size_of_val(a) % size_of::<B>() == 0 {
let new_len = core::mem::size_of_val(a) / size_of::<B>();
Ok(unsafe { core::slice::from_raw_parts(a.as_ptr() as *const B, new_len) })
} else {
Err(PodCastError::OutputSliceWouldHaveSlop)
}
}
/// Try to convert `&mut [A]` into `&mut [B]` (possibly with a change in
/// length).
///
/// As [`try_cast_slice`], but `&mut`.
#[inline]
pub(crate) unsafe fn try_cast_slice_mut<A: Copy, B: Copy>(
a: &mut [A],
) -> Result<&mut [B], PodCastError> {
// Note(Lokathor): everything with `align_of` and `size_of` will optimize away
// after monomorphization.
if align_of::<B>() > align_of::<A>()
&& !is_aligned_to(a.as_ptr() as *const (), align_of::<B>())
{
Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
} else if size_of::<B>() == size_of::<A>() {
Ok(unsafe {
core::slice::from_raw_parts_mut(a.as_mut_ptr() as *mut B, a.len())
})
} else if size_of::<A>() == 0 || size_of::<B>() == 0 {
Err(PodCastError::SizeMismatch)
} else if core::mem::size_of_val(a) % size_of::<B>() == 0 {
let new_len = core::mem::size_of_val(a) / size_of::<B>();
Ok(unsafe {
core::slice::from_raw_parts_mut(a.as_mut_ptr() as *mut B, new_len)
})
} else {
Err(PodCastError::OutputSliceWouldHaveSlop)
}
}

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#![no_std]
#![warn(missing_docs)]
#![allow(clippy::match_like_matches_macro)]
#![allow(clippy::uninlined_format_args)]
#![cfg_attr(feature = "nightly_docs", feature(doc_cfg))]
#![cfg_attr(feature = "nightly_portable_simd", feature(portable_simd))]
#![cfg_attr(feature = "nightly_stdsimd", feature(stdsimd))]
//! This crate gives small utilities for casting between plain data types.
//!
//! ## Basics
//!
//! Data comes in five basic forms in Rust, so we have five basic casting
//! functions:
//!
//! * `T` uses [`cast`]
//! * `&T` uses [`cast_ref`]
//! * `&mut T` uses [`cast_mut`]
//! * `&[T]` uses [`cast_slice`]
//! * `&mut [T]` uses [`cast_slice_mut`]
//!
//! Some casts will never fail (eg: `cast::<u32, f32>` always works), other
//! casts might fail (eg: `cast_ref::<[u8; 4], u32>` will fail if the reference
//! isn't already aligned to 4). Each casting function has a "try" version which
//! will return a `Result`, and the "normal" version which will simply panic on
//! invalid input.
//!
//! ## Using Your Own Types
//!
//! All the functions here are guarded by the [`Pod`] trait, which is a
//! sub-trait of the [`Zeroable`] trait.
//!
//! If you're very sure that your type is eligible, you can implement those
//! traits for your type and then they'll have full casting support. However,
//! these traits are `unsafe`, and you should carefully read the requirements
//! before adding the them to your own types.
//!
//! ## Features
//!
//! * This crate is core only by default, but if you're using Rust 1.36 or later
//! you can enable the `extern_crate_alloc` cargo feature for some additional
//! methods related to `Box` and `Vec`. Note that the `docs.rs` documentation
//! is always built with `extern_crate_alloc` cargo feature enabled.
#[cfg(all(target_arch = "aarch64", feature = "aarch64_simd"))]
use core::arch::aarch64;
#[cfg(all(target_arch = "wasm32", feature = "wasm_simd"))]
use core::arch::wasm32;
#[cfg(target_arch = "x86")]
use core::arch::x86;
#[cfg(target_arch = "x86_64")]
use core::arch::x86_64;
//
use core::{marker::*, mem::*, num::*, ptr::*};
// Used from macros to ensure we aren't using some locally defined name and
// actually are referencing libcore. This also would allow pre-2018 edition
// crates to use our macros, but I'm not sure how important that is.
#[doc(hidden)]
pub use ::core as __core;
#[cfg(not(feature = "min_const_generics"))]
macro_rules! impl_unsafe_marker_for_array {
( $marker:ident , $( $n:expr ),* ) => {
$(unsafe impl<T> $marker for [T; $n] where T: $marker {})*
}
}
/// A macro to transmute between two types without requiring knowing size
/// statically.
macro_rules! transmute {
($val:expr) => {
::core::mem::transmute_copy(&::core::mem::ManuallyDrop::new($val))
};
}
/// A macro to implement marker traits for various simd types.
/// #[allow(unused)] because the impls are only compiled on relevant platforms
/// with relevant cargo features enabled.
#[allow(unused)]
macro_rules! impl_unsafe_marker_for_simd {
($(#[cfg($cfg_predicate:meta)])? unsafe impl $trait:ident for $platform:ident :: {}) => {};
($(#[cfg($cfg_predicate:meta)])? unsafe impl $trait:ident for $platform:ident :: { $first_type:ident $(, $types:ident)* $(,)? }) => {
$( #[cfg($cfg_predicate)] )?
$( #[cfg_attr(feature = "nightly_docs", doc(cfg($cfg_predicate)))] )?
unsafe impl $trait for $platform::$first_type {}
$( #[cfg($cfg_predicate)] )? // To prevent recursion errors if nothing is going to be expanded anyway.
impl_unsafe_marker_for_simd!($( #[cfg($cfg_predicate)] )? unsafe impl $trait for $platform::{ $( $types ),* });
};
}
#[cfg(feature = "extern_crate_std")]
extern crate std;
#[cfg(feature = "extern_crate_alloc")]
extern crate alloc;
#[cfg(feature = "extern_crate_alloc")]
#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "extern_crate_alloc")))]
pub mod allocation;
#[cfg(feature = "extern_crate_alloc")]
pub use allocation::*;
mod anybitpattern;
pub use anybitpattern::*;
pub mod checked;
pub use checked::CheckedBitPattern;
mod internal;
mod zeroable;
pub use zeroable::*;
mod zeroable_in_option;
pub use zeroable_in_option::*;
mod pod;
pub use pod::*;
mod pod_in_option;
pub use pod_in_option::*;
#[cfg(feature = "must_cast")]
mod must;
#[cfg(feature = "must_cast")]
#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "must_cast")))]
pub use must::*;
mod no_uninit;
pub use no_uninit::*;
mod contiguous;
pub use contiguous::*;
mod offset_of;
pub use offset_of::*;
mod transparent;
pub use transparent::*;
#[cfg(feature = "derive")]
#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "derive")))]
pub use bytemuck_derive::{
AnyBitPattern, ByteEq, ByteHash, CheckedBitPattern, Contiguous, NoUninit,
Pod, TransparentWrapper, Zeroable,
};
/// The things that can go wrong when casting between [`Pod`] data forms.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum PodCastError {
/// You tried to cast a slice to an element type with a higher alignment
/// requirement but the slice wasn't aligned.
TargetAlignmentGreaterAndInputNotAligned,
/// If the element size changes then the output slice changes length
/// accordingly. If the output slice wouldn't be a whole number of elements
/// then the conversion fails.
OutputSliceWouldHaveSlop,
/// When casting a slice you can't convert between ZST elements and non-ZST
/// elements. When casting an individual `T`, `&T`, or `&mut T` value the
/// source size and destination size must be an exact match.
SizeMismatch,
/// For this type of cast the alignments must be exactly the same and they
/// were not so now you're sad.
///
/// This error is generated **only** by operations that cast allocated types
/// (such as `Box` and `Vec`), because in that case the alignment must stay
/// exact.
AlignmentMismatch,
}
#[cfg(not(target_arch = "spirv"))]
impl core::fmt::Display for PodCastError {
fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
write!(f, "{:?}", self)
}
}
#[cfg(feature = "extern_crate_std")]
#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "extern_crate_std")))]
impl std::error::Error for PodCastError {}
/// Re-interprets `&T` as `&[u8]`.
///
/// Any ZST becomes an empty slice, and in that case the pointer value of that
/// empty slice might not match the pointer value of the input reference.
#[inline]
pub fn bytes_of<T: NoUninit>(t: &T) -> &[u8] {
unsafe { internal::bytes_of(t) }
}
/// Re-interprets `&mut T` as `&mut [u8]`.
///
/// Any ZST becomes an empty slice, and in that case the pointer value of that
/// empty slice might not match the pointer value of the input reference.
#[inline]
pub fn bytes_of_mut<T: NoUninit + AnyBitPattern>(t: &mut T) -> &mut [u8] {
unsafe { internal::bytes_of_mut(t) }
}
/// Re-interprets `&[u8]` as `&T`.
///
/// ## Panics
///
/// This is [`try_from_bytes`] but will panic on error.
#[inline]
pub fn from_bytes<T: AnyBitPattern>(s: &[u8]) -> &T {
unsafe { internal::from_bytes(s) }
}
/// Re-interprets `&mut [u8]` as `&mut T`.
///
/// ## Panics
///
/// This is [`try_from_bytes_mut`] but will panic on error.
#[inline]
pub fn from_bytes_mut<T: NoUninit + AnyBitPattern>(s: &mut [u8]) -> &mut T {
unsafe { internal::from_bytes_mut(s) }
}
/// Reads from the bytes as if they were a `T`.
///
/// ## Failure
/// * If the `bytes` length is not equal to `size_of::<T>()`.
#[inline]
pub fn try_pod_read_unaligned<T: AnyBitPattern>(
bytes: &[u8],
) -> Result<T, PodCastError> {
unsafe { internal::try_pod_read_unaligned(bytes) }
}
/// Reads the slice into a `T` value.
///
/// ## Panics
/// * This is like `try_pod_read_unaligned` but will panic on failure.
#[inline]
pub fn pod_read_unaligned<T: AnyBitPattern>(bytes: &[u8]) -> T {
unsafe { internal::pod_read_unaligned(bytes) }
}
/// Re-interprets `&[u8]` as `&T`.
///
/// ## Failure
///
/// * If the slice isn't aligned for the new type
/// * If the slice's length isn’t exactly the size of the new type
#[inline]
pub fn try_from_bytes<T: AnyBitPattern>(s: &[u8]) -> Result<&T, PodCastError> {
unsafe { internal::try_from_bytes(s) }
}
/// Re-interprets `&mut [u8]` as `&mut T`.
///
/// ## Failure
///
/// * If the slice isn't aligned for the new type
/// * If the slice's length isn’t exactly the size of the new type
#[inline]
pub fn try_from_bytes_mut<T: NoUninit + AnyBitPattern>(
s: &mut [u8],
) -> Result<&mut T, PodCastError> {
unsafe { internal::try_from_bytes_mut(s) }
}
/// Cast `T` into `U`
///
/// ## Panics
///
/// * This is like [`try_cast`](try_cast), but will panic on a size mismatch.
#[inline]
pub fn cast<A: NoUninit, B: AnyBitPattern>(a: A) -> B {
unsafe { internal::cast(a) }
}
/// Cast `&mut T` into `&mut U`.
///
/// ## Panics
///
/// This is [`try_cast_mut`] but will panic on error.
#[inline]
pub fn cast_mut<A: NoUninit + AnyBitPattern, B: NoUninit + AnyBitPattern>(
a: &mut A,
) -> &mut B {
unsafe { internal::cast_mut(a) }
}
/// Cast `&T` into `&U`.
///
/// ## Panics
///
/// This is [`try_cast_ref`] but will panic on error.
#[inline]
pub fn cast_ref<A: NoUninit, B: AnyBitPattern>(a: &A) -> &B {
unsafe { internal::cast_ref(a) }
}
/// Cast `&[A]` into `&[B]`.
///
/// ## Panics
///
/// This is [`try_cast_slice`] but will panic on error.
#[inline]
pub fn cast_slice<A: NoUninit, B: AnyBitPattern>(a: &[A]) -> &[B] {
unsafe { internal::cast_slice(a) }
}
/// Cast `&mut [T]` into `&mut [U]`.
///
/// ## Panics
///
/// This is [`try_cast_slice_mut`] but will panic on error.
#[inline]
pub fn cast_slice_mut<
A: NoUninit + AnyBitPattern,
B: NoUninit + AnyBitPattern,
>(
a: &mut [A],
) -> &mut [B] {
unsafe { internal::cast_slice_mut(a) }
}
/// As `align_to`, but safe because of the [`Pod`] bound.
#[inline]
pub fn pod_align_to<T: NoUninit, U: AnyBitPattern>(
vals: &[T],
) -> (&[T], &[U], &[T]) {
unsafe { vals.align_to::<U>() }
}
/// As `align_to_mut`, but safe because of the [`Pod`] bound.
#[inline]
pub fn pod_align_to_mut<
T: NoUninit + AnyBitPattern,
U: NoUninit + AnyBitPattern,
>(
vals: &mut [T],
) -> (&mut [T], &mut [U], &mut [T]) {
unsafe { vals.align_to_mut::<U>() }
}
/// Try to cast `T` into `U`.
///
/// Note that for this particular type of cast, alignment isn't a factor. The
/// input value is semantically copied into the function and then returned to a
/// new memory location which will have whatever the required alignment of the
/// output type is.
///
/// ## Failure
///
/// * If the types don't have the same size this fails.
#[inline]
pub fn try_cast<A: NoUninit, B: AnyBitPattern>(
a: A,
) -> Result<B, PodCastError> {
unsafe { internal::try_cast(a) }
}
/// Try to convert a `&T` into `&U`.
///
/// ## Failure
///
/// * If the reference isn't aligned in the new type
/// * If the source type and target type aren't the same size.
#[inline]
pub fn try_cast_ref<A: NoUninit, B: AnyBitPattern>(
a: &A,
) -> Result<&B, PodCastError> {
unsafe { internal::try_cast_ref(a) }
}
/// Try to convert a `&mut T` into `&mut U`.
///
/// As [`try_cast_ref`], but `mut`.
#[inline]
pub fn try_cast_mut<
A: NoUninit + AnyBitPattern,
B: NoUninit + AnyBitPattern,
>(
a: &mut A,
) -> Result<&mut B, PodCastError> {
unsafe { internal::try_cast_mut(a) }
}
/// Try to convert `&[A]` into `&[B]` (possibly with a change in length).
///
/// * `input.as_ptr() as usize == output.as_ptr() as usize`
/// * `input.len() * size_of::<A>() == output.len() * size_of::<B>()`
///
/// ## Failure
///
/// * If the target type has a greater alignment requirement and the input slice
/// isn't aligned.
/// * If the target element type is a different size from the current element
/// type, and the output slice wouldn't be a whole number of elements when
/// accounting for the size change (eg: 3 `u16` values is 1.5 `u32` values, so
/// that's a failure).
/// * Similarly, you can't convert between a [ZST](https://doc.rust-lang.org/nomicon/exotic-sizes.html#zero-sized-types-zsts)
/// and a non-ZST.
#[inline]
pub fn try_cast_slice<A: NoUninit, B: AnyBitPattern>(
a: &[A],
) -> Result<&[B], PodCastError> {
unsafe { internal::try_cast_slice(a) }
}
/// Try to convert `&mut [A]` into `&mut [B]` (possibly with a change in
/// length).
///
/// As [`try_cast_slice`], but `&mut`.
#[inline]
pub fn try_cast_slice_mut<
A: NoUninit + AnyBitPattern,
B: NoUninit + AnyBitPattern,
>(
a: &mut [A],
) -> Result<&mut [B], PodCastError> {
unsafe { internal::try_cast_slice_mut(a) }
}
/// Fill all bytes of `target` with zeroes (see [`Zeroable`]).
///
/// This is similar to `*target = Zeroable::zeroed()`, but guarantees that any
/// padding bytes in `target` are zeroed as well.
///
/// See also [`fill_zeroes`], if you have a slice rather than a single value.
#[inline]
pub fn write_zeroes<T: Zeroable>(target: &mut T) {
struct EnsureZeroWrite<T>(*mut T);
impl<T> Drop for EnsureZeroWrite<T> {
#[inline(always)]
fn drop(&mut self) {
unsafe {
core::ptr::write_bytes(self.0, 0u8, 1);
}
}
}
unsafe {
let guard = EnsureZeroWrite(target);
core::ptr::drop_in_place(guard.0);
drop(guard);
}
}
/// Fill all bytes of `slice` with zeroes (see [`Zeroable`]).
///
/// This is similar to `slice.fill(Zeroable::zeroed())`, but guarantees that any
/// padding bytes in `slice` are zeroed as well.
///
/// See also [`write_zeroes`], which zeroes all bytes of a single value rather
/// than a slice.
#[inline]
pub fn fill_zeroes<T: Zeroable>(slice: &mut [T]) {
if core::mem::needs_drop::<T>() {
// If `T` needs to be dropped then we have to do this one item at a time, in
// case one of the intermediate drops does a panic.
slice.iter_mut().for_each(write_zeroes);
} else {
// Otherwise we can be really fast and just fill everthing with zeros.
let len = core::mem::size_of_val::<[T]>(slice);
unsafe { core::ptr::write_bytes(slice.as_mut_ptr() as *mut u8, 0u8, len) }
}
}

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#![allow(clippy::module_name_repetitions)]
#![allow(clippy::let_unit_value)]
#![allow(clippy::let_underscore_untyped)]
#![allow(clippy::ptr_as_ptr)]
use crate::{AnyBitPattern, NoUninit};
use core::mem::{align_of, size_of};
struct Cast<A, B>((A, B));
impl<A, B> Cast<A, B> {
const ASSERT_ALIGN_GREATER_THAN_EQUAL: () =
assert!(align_of::<A>() >= align_of::<B>());
const ASSERT_SIZE_EQUAL: () = assert!(size_of::<A>() == size_of::<B>());
const ASSERT_SIZE_MULTIPLE_OF: () = assert!(
(size_of::<A>() == 0) == (size_of::<B>() == 0)
&& (size_of::<A>() % size_of::<B>() == 0)
);
}
// Workaround for https://github.com/rust-lang/miri/issues/2423.
// Miri currently doesn't see post-monomorphization errors until runtime,
// so `compile_fail` tests relying on post-monomorphization errors don't
// actually fail. Instead use `should_panic` under miri as a workaround.
#[cfg(miri)]
macro_rules! post_mono_compile_fail_doctest {
() => {
"```should_panic"
};
}
#[cfg(not(miri))]
macro_rules! post_mono_compile_fail_doctest {
() => {
"```compile_fail,E0080"
};
}
/// Cast `A` into `B` if infalliable, or fail to compile.
///
/// Note that for this particular type of cast, alignment isn't a factor. The
/// input value is semantically copied into the function and then returned to a
/// new memory location which will have whatever the required alignment of the
/// output type is.
///
/// ## Failure
///
/// * If the types don't have the same size this fails to compile.
///
/// ## Examples
/// ```
/// // compiles:
/// let bytes: [u8; 2] = bytemuck::must_cast(12_u16);
/// ```
#[doc = post_mono_compile_fail_doctest!()]
/// // fails to compile (size mismatch):
/// let bytes : [u8; 3] = bytemuck::must_cast(12_u16);
/// ```
#[inline]
pub fn must_cast<A: NoUninit, B: AnyBitPattern>(a: A) -> B {
let _ = Cast::<A, B>::ASSERT_SIZE_EQUAL;
unsafe { transmute!(a) }
}
/// Convert `&A` into `&B` if infalliable, or fail to compile.
///
/// ## Failure
///
/// * If the target type has a greater alignment requirement.
/// * If the source type and target type aren't the same size.
///
/// ## Examples
/// ```
/// // compiles:
/// let bytes: &[u8; 2] = bytemuck::must_cast_ref(&12_u16);
/// ```
#[doc = post_mono_compile_fail_doctest!()]
/// // fails to compile (size mismatch):
/// let bytes : &[u8; 3] = bytemuck::must_cast_ref(&12_u16);
/// ```
#[doc = post_mono_compile_fail_doctest!()]
/// // fails to compile (alignment requirements increased):
/// let bytes : &u16 = bytemuck::must_cast_ref(&[1u8, 2u8]);
/// ```
#[inline]
pub fn must_cast_ref<A: NoUninit, B: AnyBitPattern>(a: &A) -> &B {
let _ = Cast::<A, B>::ASSERT_SIZE_EQUAL;
let _ = Cast::<A, B>::ASSERT_ALIGN_GREATER_THAN_EQUAL;
unsafe { &*(a as *const A as *const B) }
}
/// Convert a `&mut A` into `&mut B` if infalliable, or fail to compile.
///
/// As [`must_cast_ref`], but `mut`.
///
/// ## Examples
/// ```
/// let mut i = 12_u16;
/// // compiles:
/// let bytes: &mut [u8; 2] = bytemuck::must_cast_mut(&mut i);
/// ```
#[doc = post_mono_compile_fail_doctest!()]
/// # let mut bytes: &mut [u8; 2] = &mut [1, 2];
/// // fails to compile (alignment requirements increased):
/// let i : &mut u16 = bytemuck::must_cast_mut(bytes);
/// ```
#[doc = post_mono_compile_fail_doctest!()]
/// # let mut i = 12_u16;
/// // fails to compile (size mismatch):
/// let bytes : &mut [u8; 3] = bytemuck::must_cast_mut(&mut i);
/// ```
#[inline]
pub fn must_cast_mut<
A: NoUninit + AnyBitPattern,
B: NoUninit + AnyBitPattern,
>(
a: &mut A,
) -> &mut B {
let _ = Cast::<A, B>::ASSERT_SIZE_EQUAL;
let _ = Cast::<A, B>::ASSERT_ALIGN_GREATER_THAN_EQUAL;
unsafe { &mut *(a as *mut A as *mut B) }
}
/// Convert `&[A]` into `&[B]` (possibly with a change in length) if
/// infalliable, or fail to compile.
///
/// * `input.as_ptr() as usize == output.as_ptr() as usize`
/// * `input.len() * size_of::<A>() == output.len() * size_of::<B>()`
///
/// ## Failure
///
/// * If the target type has a greater alignment requirement.
/// * If the target element type doesn't evenly fit into the the current element
/// type (eg: 3 `u16` values is 1.5 `u32` values, so that's a failure).
/// * Similarly, you can't convert between a [ZST](https://doc.rust-lang.org/nomicon/exotic-sizes.html#zero-sized-types-zsts)
/// and a non-ZST.
///
/// ## Examples
/// ```
/// let indicies: &[u16] = &[1, 2, 3];
/// // compiles:
/// let bytes: &[u8] = bytemuck::must_cast_slice(indicies);
/// ```
#[doc = post_mono_compile_fail_doctest!()]
/// # let bytes : &[u8] = &[1, 0, 2, 0, 3, 0];
/// // fails to compile (bytes.len() might not be a multiple of 2):
/// let byte_pairs : &[[u8; 2]] = bytemuck::must_cast_slice(bytes);
/// ```
#[doc = post_mono_compile_fail_doctest!()]
/// # let byte_pairs : &[[u8; 2]] = &[[1, 0], [2, 0], [3, 0]];
/// // fails to compile (alignment requirements increased):
/// let indicies : &[u16] = bytemuck::must_cast_slice(byte_pairs);
/// ```
#[inline]
pub fn must_cast_slice<A: NoUninit, B: AnyBitPattern>(a: &[A]) -> &[B] {
let _ = Cast::<A, B>::ASSERT_SIZE_MULTIPLE_OF;
let _ = Cast::<A, B>::ASSERT_ALIGN_GREATER_THAN_EQUAL;
let new_len = if size_of::<A>() == size_of::<B>() {
a.len()
} else {
a.len() * (size_of::<A>() / size_of::<B>())
};
unsafe { core::slice::from_raw_parts(a.as_ptr() as *const B, new_len) }
}
/// Convert `&mut [A]` into `&mut [B]` (possibly with a change in length) if
/// infalliable, or fail to compile.
///
/// As [`must_cast_slice`], but `&mut`.
///
/// ## Examples
/// ```
/// let mut indicies = [1, 2, 3];
/// let indicies: &mut [u16] = &mut indicies;
/// // compiles:
/// let bytes: &mut [u8] = bytemuck::must_cast_slice_mut(indicies);
/// ```
#[doc = post_mono_compile_fail_doctest!()]
/// # let mut bytes = [1, 0, 2, 0, 3, 0];
/// # let bytes : &mut [u8] = &mut bytes[..];
/// // fails to compile (bytes.len() might not be a multiple of 2):
/// let byte_pairs : &mut [[u8; 2]] = bytemuck::must_cast_slice_mut(bytes);
/// ```
#[doc = post_mono_compile_fail_doctest!()]
/// # let mut byte_pairs = [[1, 0], [2, 0], [3, 0]];
/// # let byte_pairs : &mut [[u8; 2]] = &mut byte_pairs[..];
/// // fails to compile (alignment requirements increased):
/// let indicies : &mut [u16] = bytemuck::must_cast_slice_mut(byte_pairs);
/// ```
#[inline]
pub fn must_cast_slice_mut<
A: NoUninit + AnyBitPattern,
B: NoUninit + AnyBitPattern,
>(
a: &mut [A],
) -> &mut [B] {
let _ = Cast::<A, B>::ASSERT_SIZE_MULTIPLE_OF;
let _ = Cast::<A, B>::ASSERT_ALIGN_GREATER_THAN_EQUAL;
let new_len = if size_of::<A>() == size_of::<B>() {
a.len()
} else {
a.len() * (size_of::<A>() / size_of::<B>())
};
unsafe { core::slice::from_raw_parts_mut(a.as_mut_ptr() as *mut B, new_len) }
}

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use crate::Pod;
use core::num::{
NonZeroI128, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI8, NonZeroIsize,
NonZeroU128, NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8, NonZeroUsize,
};
/// Marker trait for "plain old data" types with no uninit (or padding) bytes.
///
/// The requirements for this is very similar to [`Pod`],
/// except that it doesn't require that all bit patterns of the type are valid,
/// i.e. it does not require the type to be [`Zeroable`][crate::Zeroable].
/// This limits what you can do with a type of this kind, but also broadens the
/// included types to things like C-style enums. Notably, you can only cast from
/// *immutable* references to a [`NoUninit`] type into *immutable* references of
/// any other type, no casting of mutable references or mutable references to
/// slices etc.
///
/// [`Pod`] is a subset of [`NoUninit`], meaning that any `T: Pod` is also
/// [`NoUninit`] but any `T: NoUninit` is not necessarily [`Pod`]. If possible,
/// prefer implementing [`Pod`] directly. To get more [`Pod`]-like functionality
/// for a type that is only [`NoUninit`], consider also implementing
/// [`CheckedBitPattern`][crate::CheckedBitPattern].
///
/// # Derive
///
/// A `#[derive(NoUninit)]` macro is provided under the `derive` feature flag
/// which will automatically validate the requirements of this trait and
/// implement the trait for you for both enums and structs. This is the
/// recommended method for implementing the trait, however it's also possible to
/// do manually. If you implement it manually, you *must* carefully follow the
/// below safety rules.
///
/// # Safety
///
/// The same as [`Pod`] except we disregard the rule about it must
/// allow any bit pattern (i.e. it does not need to be
/// [`Zeroable`][crate::Zeroable]). Still, this is a quite strong guarantee
/// about a type, so *be careful* whem implementing it manually.
///
/// * The type must be inhabited (eg: no
/// [Infallible](core::convert::Infallible)).
/// * The type must not contain any uninit (or padding) bytes, either in the
/// middle or on the end (eg: no `#[repr(C)] struct Foo(u8, u16)`, which has
/// padding in the middle, and also no `#[repr(C)] struct Foo(u16, u8)`, which
/// has padding on the end).
/// * Structs need to have all fields also be `NoUninit`.
/// * Structs need to be `repr(C)` or `repr(transparent)`. In the case of
/// `repr(C)`, the `packed` and `align` repr modifiers can be used as long as
/// all other rules end up being followed.
/// * Enums need to have an explicit `#[repr(Int)]`
/// * Enums must have only fieldless variants
/// * It is disallowed for types to contain pointer types, `Cell`, `UnsafeCell`,
/// atomics, and any other forms of interior mutability.
/// * More precisely: A shared reference to the type must allow reads, and
/// *only* reads. RustBelt's separation logic is based on the notion that a
/// type is allowed to define a sharing predicate, its own invariant that must
/// hold for shared references, and this predicate is the reasoning that allow
/// it to deal with atomic and cells etc. We require the sharing predicate to
/// be trivial and permit only read-only access.
/// * There's probably more, don't mess it up (I mean it).
pub unsafe trait NoUninit: Sized + Copy + 'static {}
unsafe impl<T: Pod> NoUninit for T {}
unsafe impl NoUninit for char {}
unsafe impl NoUninit for bool {}
unsafe impl NoUninit for NonZeroU8 {}
unsafe impl NoUninit for NonZeroI8 {}
unsafe impl NoUninit for NonZeroU16 {}
unsafe impl NoUninit for NonZeroI16 {}
unsafe impl NoUninit for NonZeroU32 {}
unsafe impl NoUninit for NonZeroI32 {}
unsafe impl NoUninit for NonZeroU64 {}
unsafe impl NoUninit for NonZeroI64 {}
unsafe impl NoUninit for NonZeroU128 {}
unsafe impl NoUninit for NonZeroI128 {}
unsafe impl NoUninit for NonZeroUsize {}
unsafe impl NoUninit for NonZeroIsize {}

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#![forbid(unsafe_code)]
/// Find the offset in bytes of the given `$field` of `$Type`. Requires an
/// already initialized `$instance` value to work with.
///
/// This is similar to the macro from [`memoffset`](https://docs.rs/memoffset),
/// however it uses no `unsafe` code.
///
/// This macro has a 3-argument and 2-argument version.
/// * In the 3-arg version you specify an instance of the type, the type itself,
/// and the field name.
/// * In the 2-arg version the macro will call the [`default`](Default::default)
/// method to make a temporary instance of the type for you.
///
/// The output of this macro is the byte offset of the field (as a `usize`). The
/// calculations of the macro are fixed across the entire program, but if the
/// type used is `repr(Rust)` then they're *not* fixed across compilations or
/// compilers.
///
/// ## Examples
///
/// ### 3-arg Usage
///
/// ```rust
/// # use bytemuck::offset_of;
/// // enums can't derive default, and for this example we don't pick one
/// enum MyExampleEnum {
/// A,
/// B,
/// C,
/// }
///
/// // so now our struct here doesn't have Default
/// #[repr(C)]
/// struct MyNotDefaultType {
/// pub counter: i32,
/// pub some_field: MyExampleEnum,
/// }
///
/// // but we provide an instance of the type and it's all good.
/// let val = MyNotDefaultType { counter: 5, some_field: MyExampleEnum::A };
/// assert_eq!(offset_of!(val, MyNotDefaultType, some_field), 4);
/// ```
///
/// ### 2-arg Usage
///
/// ```rust
/// # use bytemuck::offset_of;
/// #[derive(Default)]
/// #[repr(C)]
/// struct Vertex {
/// pub loc: [f32; 3],
/// pub color: [f32; 3],
/// }
/// // if the type impls Default the macro can make its own default instance.
/// assert_eq!(offset_of!(Vertex, loc), 0);
/// assert_eq!(offset_of!(Vertex, color), 12);
/// ```
///
/// # Usage with `#[repr(packed)]` structs
///
/// Attempting to compute the offset of a `#[repr(packed)]` struct with
/// `bytemuck::offset_of!` requires an `unsafe` block. We hope to relax this in
/// the future, but currently it is required to work around a soundness hole in
/// Rust (See [rust-lang/rust#27060]).
///
/// [rust-lang/rust#27060]: https://github.com/rust-lang/rust/issues/27060
///
/// <p style="background:rgba(255,181,77,0.16);padding:0.75em;">
/// <strong>Warning:</strong> This is only true for versions of bytemuck >
/// 1.4.0. Previous versions of
/// <code style="background:rgba(41,24,0,0.1);">bytemuck::offset_of!</code>
/// will only emit a warning when used on the field of a packed struct in safe
/// code, which can lead to unsoundness.
/// </p>
///
/// For example, the following will fail to compile:
///
/// ```compile_fail
/// #[repr(C, packed)]
/// #[derive(Default)]
/// struct Example {
/// field: u32,
/// }
/// // Doesn't compile:
/// let _offset = bytemuck::offset_of!(Example, field);
/// ```
///
/// While the error message this generates will mention the
/// `safe_packed_borrows` lint, the macro will still fail to compile even if
/// that lint is `#[allow]`ed:
///
/// ```compile_fail
/// # #[repr(C, packed)] #[derive(Default)] struct Example { field: u32 }
/// // Still doesn't compile:
/// #[allow(safe_packed_borrows)]
/// {
/// let _offset = bytemuck::offset_of!(Example, field);
/// }
/// ```
///
/// This *can* be worked around by using `unsafe`, but it is only sound to do so
/// if you can guarantee that taking a reference to the field is sound.
///
/// In practice, this means it only works for fields of align(1) types, or if
/// you know the field's offset in advance (defeating the point of `offset_of`)
/// and can prove that the struct's alignment and the field's offset are enough
/// to prove the field's alignment.
///
/// Once the `raw_ref` macros are available, a future version of this crate will
/// use them to lift the limitations of packed structs. For the duration of the
/// `1.x` version of this crate that will be behind an on-by-default cargo
/// feature (to maintain minimum rust version support).
#[macro_export]
macro_rules! offset_of {
($instance:expr, $Type:path, $field:tt) => {{
#[forbid(safe_packed_borrows)]
{
// This helps us guard against field access going through a Deref impl.
#[allow(clippy::unneeded_field_pattern)]
let $Type { $field: _, .. };
let reference: &$Type = &$instance;
let address = reference as *const _ as usize;
let field_pointer = &reference.$field as *const _ as usize;
// These asserts/unwraps are compiled away at release, and defend against
// the case where somehow a deref impl is still invoked.
let result = field_pointer.checked_sub(address).unwrap();
assert!(result <= $crate::__core::mem::size_of::<$Type>());
result
}
}};
($Type:path, $field:tt) => {{
$crate::offset_of!(<$Type as Default>::default(), $Type, $field)
}};
}

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use super::*;
/// Marker trait for "plain old data".
///
/// The point of this trait is that once something is marked "plain old data"
/// you can really go to town with the bit fiddling and bit casting. Therefore,
/// it's a relatively strong claim to make about a type. Do not add this to your
/// type casually.
///
/// **Reminder:** The results of casting around bytes between data types are
/// _endian dependant_. Little-endian machines are the most common, but
/// big-endian machines do exist (and big-endian is also used for "network
/// order" bytes).
///
/// ## Safety
///
/// * The type must be inhabited (eg: no
/// [Infallible](core::convert::Infallible)).
/// * The type must allow any bit pattern (eg: no `bool` or `char`, which have
/// illegal bit patterns).
/// * The type must not contain any uninit (or padding) bytes, either in the
/// middle or on the end (eg: no `#[repr(C)] struct Foo(u8, u16)`, which has
/// padding in the middle, and also no `#[repr(C)] struct Foo(u16, u8)`, which
/// has padding on the end).
/// * The type needs to have all fields also be `Pod`.
/// * The type needs to be `repr(C)` or `repr(transparent)`. In the case of
/// `repr(C)`, the `packed` and `align` repr modifiers can be used as long as
/// all other rules end up being followed.
/// * It is disallowed for types to contain pointer types, `Cell`, `UnsafeCell`,
/// atomics, and any other forms of interior mutability.
/// * More precisely: A shared reference to the type must allow reads, and
/// *only* reads. RustBelt's separation logic is based on the notion that a
/// type is allowed to define a sharing predicate, its own invariant that must
/// hold for shared references, and this predicate is the reasoning that allow
/// it to deal with atomic and cells etc. We require the sharing predicate to
/// be trivial and permit only read-only access.
pub unsafe trait Pod: Zeroable + Copy + 'static {}
unsafe impl Pod for () {}
unsafe impl Pod for u8 {}
unsafe impl Pod for i8 {}
unsafe impl Pod for u16 {}
unsafe impl Pod for i16 {}
unsafe impl Pod for u32 {}
unsafe impl Pod for i32 {}
unsafe impl Pod for u64 {}
unsafe impl Pod for i64 {}
unsafe impl Pod for usize {}
unsafe impl Pod for isize {}
unsafe impl Pod for u128 {}
unsafe impl Pod for i128 {}
unsafe impl Pod for f32 {}
unsafe impl Pod for f64 {}
unsafe impl<T: Pod> Pod for Wrapping<T> {}
#[cfg(feature = "unsound_ptr_pod_impl")]
#[cfg_attr(
feature = "nightly_docs",
doc(cfg(feature = "unsound_ptr_pod_impl"))
)]
unsafe impl<T: 'static> Pod for *mut T {}
#[cfg(feature = "unsound_ptr_pod_impl")]
#[cfg_attr(
feature = "nightly_docs",
doc(cfg(feature = "unsound_ptr_pod_impl"))
)]
unsafe impl<T: 'static> Pod for *const T {}
#[cfg(feature = "unsound_ptr_pod_impl")]
#[cfg_attr(
feature = "nightly_docs",
doc(cfg(feature = "unsound_ptr_pod_impl"))
)]
unsafe impl<T: 'static> PodInOption for NonNull<T> {}
unsafe impl<T: ?Sized + 'static> Pod for PhantomData<T> {}
unsafe impl Pod for PhantomPinned {}
unsafe impl<T: Pod> Pod for ManuallyDrop<T> {}
// Note(Lokathor): MaybeUninit can NEVER be Pod.
#[cfg(feature = "min_const_generics")]
#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "min_const_generics")))]
unsafe impl<T, const N: usize> Pod for [T; N] where T: Pod {}
#[cfg(not(feature = "min_const_generics"))]
impl_unsafe_marker_for_array!(
Pod, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 48, 64, 96, 128, 256,
512, 1024, 2048, 4096
);
impl_unsafe_marker_for_simd!(
#[cfg(all(target_arch = "wasm32", feature = "wasm_simd"))]
unsafe impl Pod for wasm32::{v128}
);
impl_unsafe_marker_for_simd!(
#[cfg(all(target_arch = "aarch64", feature = "aarch64_simd"))]
unsafe impl Pod for aarch64::{
float32x2_t, float32x2x2_t, float32x2x3_t, float32x2x4_t, float32x4_t,
float32x4x2_t, float32x4x3_t, float32x4x4_t, float64x1_t, float64x1x2_t,
float64x1x3_t, float64x1x4_t, float64x2_t, float64x2x2_t, float64x2x3_t,
float64x2x4_t, int16x4_t, int16x4x2_t, int16x4x3_t, int16x4x4_t, int16x8_t,
int16x8x2_t, int16x8x3_t, int16x8x4_t, int32x2_t, int32x2x2_t, int32x2x3_t,
int32x2x4_t, int32x4_t, int32x4x2_t, int32x4x3_t, int32x4x4_t, int64x1_t,
int64x1x2_t, int64x1x3_t, int64x1x4_t, int64x2_t, int64x2x2_t, int64x2x3_t,
int64x2x4_t, int8x16_t, int8x16x2_t, int8x16x3_t, int8x16x4_t, int8x8_t,
int8x8x2_t, int8x8x3_t, int8x8x4_t, poly16x4_t, poly16x4x2_t, poly16x4x3_t,
poly16x4x4_t, poly16x8_t, poly16x8x2_t, poly16x8x3_t, poly16x8x4_t,
poly64x1_t, poly64x1x2_t, poly64x1x3_t, poly64x1x4_t, poly64x2_t,
poly64x2x2_t, poly64x2x3_t, poly64x2x4_t, poly8x16_t, poly8x16x2_t,
poly8x16x3_t, poly8x16x4_t, poly8x8_t, poly8x8x2_t, poly8x8x3_t, poly8x8x4_t,
uint16x4_t, uint16x4x2_t, uint16x4x3_t, uint16x4x4_t, uint16x8_t,
uint16x8x2_t, uint16x8x3_t, uint16x8x4_t, uint32x2_t, uint32x2x2_t,
uint32x2x3_t, uint32x2x4_t, uint32x4_t, uint32x4x2_t, uint32x4x3_t,
uint32x4x4_t, uint64x1_t, uint64x1x2_t, uint64x1x3_t, uint64x1x4_t,
uint64x2_t, uint64x2x2_t, uint64x2x3_t, uint64x2x4_t, uint8x16_t,
uint8x16x2_t, uint8x16x3_t, uint8x16x4_t, uint8x8_t, uint8x8x2_t,
uint8x8x3_t, uint8x8x4_t,
}
);
impl_unsafe_marker_for_simd!(
#[cfg(target_arch = "x86")]
unsafe impl Pod for x86::{
__m128i, __m128, __m128d,
__m256i, __m256, __m256d,
}
);
impl_unsafe_marker_for_simd!(
#[cfg(target_arch = "x86_64")]
unsafe impl Pod for x86_64::{
__m128i, __m128, __m128d,
__m256i, __m256, __m256d,
}
);
#[cfg(feature = "nightly_portable_simd")]
#[cfg_attr(
feature = "nightly_docs",
doc(cfg(feature = "nightly_portable_simd"))
)]
unsafe impl<T, const N: usize> Pod for core::simd::Simd<T, N>
where
T: core::simd::SimdElement + Pod,
core::simd::LaneCount<N>: core::simd::SupportedLaneCount,
{
}
impl_unsafe_marker_for_simd!(
#[cfg(all(target_arch = "x86", feature = "nightly_stdsimd"))]
unsafe impl Pod for x86::{
__m128bh, __m256bh, __m512,
__m512bh, __m512d, __m512i,
}
);
impl_unsafe_marker_for_simd!(
#[cfg(all(target_arch = "x86_64", feature = "nightly_stdsimd"))]
unsafe impl Pod for x86_64::{
__m128bh, __m256bh, __m512,
__m512bh, __m512d, __m512i,
}
);

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use super::*;
// Note(Lokathor): This is the neat part!!
unsafe impl<T: PodInOption> Pod for Option<T> {}
/// Trait for types which are [Pod](Pod) when wrapped in
/// [Option](core::option::Option).
///
/// ## Safety
///
/// * `Option<T>` must uphold the same invariants as [Pod](Pod).
/// * **Reminder:** pointers are **not** pod! **Do not** mix this trait with a
/// newtype over [NonNull](core::ptr::NonNull).
pub unsafe trait PodInOption: ZeroableInOption + Copy + 'static {}
unsafe impl PodInOption for NonZeroI8 {}
unsafe impl PodInOption for NonZeroI16 {}
unsafe impl PodInOption for NonZeroI32 {}
unsafe impl PodInOption for NonZeroI64 {}
unsafe impl PodInOption for NonZeroI128 {}
unsafe impl PodInOption for NonZeroIsize {}
unsafe impl PodInOption for NonZeroU8 {}
unsafe impl PodInOption for NonZeroU16 {}
unsafe impl PodInOption for NonZeroU32 {}
unsafe impl PodInOption for NonZeroU64 {}
unsafe impl PodInOption for NonZeroU128 {}
unsafe impl PodInOption for NonZeroUsize {}

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use super::*;
/// A trait which indicates that a type is a `#[repr(transparent)]` wrapper
/// around the `Inner` value.
///
/// This allows safely copy transmuting between the `Inner` type and the
/// `TransparentWrapper` type. Functions like `wrap_{}` convert from the inner
/// type to the wrapper type and `peel_{}` functions do the inverse conversion
/// from the wrapper type to the inner type. We deliberately do not call the
/// wrapper-removing methods "unwrap" because at this point that word is too
/// strongly tied to the Option/ Result methods.
///
/// # Safety
///
/// The safety contract of `TransparentWrapper` is relatively simple:
///
/// For a given `Wrapper` which implements `TransparentWrapper<Inner>`:
///
/// 1. `Wrapper` must be a wrapper around `Inner` with an identical data
/// representations. This either means that it must be a
/// `#[repr(transparent)]` struct which contains a either a field of type
/// `Inner` (or a field of some other transparent wrapper for `Inner`) as
/// the only non-ZST field.
///
/// 2. Any fields *other* than the `Inner` field must be trivially constructable
/// ZSTs, for example `PhantomData`, `PhantomPinned`, etc. (When deriving
/// `TransparentWrapper` on a type with ZST fields, the ZST fields must be
/// [`Zeroable`]).
///
/// 3. The `Wrapper` may not impose additional alignment requirements over
/// `Inner`.
/// - Note: this is currently guaranteed by `repr(transparent)`, but there
/// have been discussions of lifting it, so it's stated here explicitly.
///
/// 4. All functions on `TransparentWrapper` **may not** be overridden.
///
/// ## Caveats
///
/// If the wrapper imposes additional constraints upon the inner type which are
/// required for safety, it's responsible for ensuring those still hold -- this
/// generally requires preventing access to instances of the inner type, as
/// implementing `TransparentWrapper<U> for T` means anybody can call
/// `T::cast_ref(any_instance_of_u)`.
///
/// For example, it would be invalid to implement TransparentWrapper for `str`
/// to implement `TransparentWrapper` around `[u8]` because of this.
///
/// # Examples
///
/// ## Basic
///
/// ```
/// use bytemuck::TransparentWrapper;
/// # #[derive(Default)]
/// # struct SomeStruct(u32);
///
/// #[repr(transparent)]
/// struct MyWrapper(SomeStruct);
///
/// unsafe impl TransparentWrapper<SomeStruct> for MyWrapper {}
///
/// // interpret a reference to &SomeStruct as a &MyWrapper
/// let thing = SomeStruct::default();
/// let inner_ref: &MyWrapper = MyWrapper::wrap_ref(&thing);
///
/// // Works with &mut too.
/// let mut mut_thing = SomeStruct::default();
/// let inner_mut: &mut MyWrapper = MyWrapper::wrap_mut(&mut mut_thing);
///
/// # let _ = (inner_ref, inner_mut); // silence warnings
/// ```
///
/// ## Use with dynamically sized types
///
/// ```
/// use bytemuck::TransparentWrapper;
///
/// #[repr(transparent)]
/// struct Slice<T>([T]);
///
/// unsafe impl<T> TransparentWrapper<[T]> for Slice<T> {}
///
/// let s = Slice::wrap_ref(&[1u32, 2, 3]);
/// assert_eq!(&s.0, &[1, 2, 3]);
///
/// let mut buf = [1, 2, 3u8];
/// let sm = Slice::wrap_mut(&mut buf);
/// ```
///
/// ## Deriving
///
/// When deriving, the non-wrapped fields must uphold all the normal requirements,
/// and must also be `Zeroable`.
///
#[cfg_attr(feature = "derive", doc = "```")]
#[cfg_attr(
not(feature = "derive"),
doc = "```ignore
// This example requires the `derive` feature."
)]
/// use bytemuck::TransparentWrapper;
/// use std::marker::PhantomData;
///
/// #[derive(TransparentWrapper)]
/// #[repr(transparent)]
/// #[transparent(usize)]
/// struct Wrapper<T: ?Sized>(usize, PhantomData<T>); // PhantomData<T> implements Zeroable for all T
/// ```
///
/// Here, an error will occur, because `MyZst` does not implement `Zeroable`.
///
#[cfg_attr(feature = "derive", doc = "```compile_fail")]
#[cfg_attr(
not(feature = "derive"),
doc = "```ignore
// This example requires the `derive` feature."
)]
/// use bytemuck::TransparentWrapper;
/// struct MyZst;
///
/// #[derive(TransparentWrapper)]
/// #[repr(transparent)]
/// #[transparent(usize)]
/// struct Wrapper(usize, MyZst); // MyZst does not implement Zeroable
/// ```
pub unsafe trait TransparentWrapper<Inner: ?Sized> {
/// Convert the inner type into the wrapper type.
#[inline]
fn wrap(s: Inner) -> Self
where
Self: Sized,
Inner: Sized,
{
// SAFETY: The unsafe contract requires that `Self` and `Inner` have
// identical representations.
unsafe { transmute!(s) }
}
/// Convert a reference to the inner type into a reference to the wrapper
/// type.
#[inline]
fn wrap_ref(s: &Inner) -> &Self {
unsafe {
assert!(size_of::<*const Inner>() == size_of::<*const Self>());
// A pointer cast doesn't work here because rustc can't tell that
// the vtables match (because of the `?Sized` restriction relaxation).
// A `transmute` doesn't work because the sizes are unspecified.
//
// SAFETY: The unsafe contract requires that these two have
// identical representations.
let inner_ptr = s as *const Inner;
let wrapper_ptr: *const Self = transmute!(inner_ptr);
&*wrapper_ptr
}
}
/// Convert a mutable reference to the inner type into a mutable reference to
/// the wrapper type.
#[inline]
fn wrap_mut(s: &mut Inner) -> &mut Self {
unsafe {
assert!(size_of::<*mut Inner>() == size_of::<*mut Self>());
// A pointer cast doesn't work here because rustc can't tell that
// the vtables match (because of the `?Sized` restriction relaxation).
// A `transmute` doesn't work because the sizes are unspecified.
//
// SAFETY: The unsafe contract requires that these two have
// identical representations.
let inner_ptr = s as *mut Inner;
let wrapper_ptr: *mut Self = transmute!(inner_ptr);
&mut *wrapper_ptr
}
}
/// Convert a slice to the inner type into a slice to the wrapper type.
#[inline]
fn wrap_slice(s: &[Inner]) -> &[Self]
where
Self: Sized,
Inner: Sized,
{
unsafe {
assert!(size_of::<*const Inner>() == size_of::<*const Self>());
assert!(align_of::<*const Inner>() == align_of::<*const Self>());
// SAFETY: The unsafe contract requires that these two have
// identical representations (size and alignment).
core::slice::from_raw_parts(s.as_ptr() as *const Self, s.len())
}
}
/// Convert a mutable slice to the inner type into a mutable slice to the
/// wrapper type.
#[inline]
fn wrap_slice_mut(s: &mut [Inner]) -> &mut [Self]
where
Self: Sized,
Inner: Sized,
{
unsafe {
assert!(size_of::<*mut Inner>() == size_of::<*mut Self>());
assert!(align_of::<*mut Inner>() == align_of::<*mut Self>());
// SAFETY: The unsafe contract requires that these two have
// identical representations (size and alignment).
core::slice::from_raw_parts_mut(s.as_mut_ptr() as *mut Self, s.len())
}
}
/// Convert the wrapper type into the inner type.
#[inline]
fn peel(s: Self) -> Inner
where
Self: Sized,
Inner: Sized,
{
unsafe { transmute!(s) }
}
/// Convert a reference to the wrapper type into a reference to the inner
/// type.
#[inline]
fn peel_ref(s: &Self) -> &Inner {
unsafe {
assert!(size_of::<*const Inner>() == size_of::<*const Self>());
// A pointer cast doesn't work here because rustc can't tell that
// the vtables match (because of the `?Sized` restriction relaxation).
// A `transmute` doesn't work because the sizes are unspecified.
//
// SAFETY: The unsafe contract requires that these two have
// identical representations.
let wrapper_ptr = s as *const Self;
let inner_ptr: *const Inner = transmute!(wrapper_ptr);
&*inner_ptr
}
}
/// Convert a mutable reference to the wrapper type into a mutable reference
/// to the inner type.
#[inline]
fn peel_mut(s: &mut Self) -> &mut Inner {
unsafe {
assert!(size_of::<*mut Inner>() == size_of::<*mut Self>());
// A pointer cast doesn't work here because rustc can't tell that
// the vtables match (because of the `?Sized` restriction relaxation).
// A `transmute` doesn't work because the sizes are unspecified.
//
// SAFETY: The unsafe contract requires that these two have
// identical representations.
let wrapper_ptr = s as *mut Self;
let inner_ptr: *mut Inner = transmute!(wrapper_ptr);
&mut *inner_ptr
}
}
/// Convert a slice to the wrapped type into a slice to the inner type.
#[inline]
fn peel_slice(s: &[Self]) -> &[Inner]
where
Self: Sized,
Inner: Sized,
{
unsafe {
assert!(size_of::<*const Inner>() == size_of::<*const Self>());
assert!(align_of::<*const Inner>() == align_of::<*const Self>());
// SAFETY: The unsafe contract requires that these two have
// identical representations (size and alignment).
core::slice::from_raw_parts(s.as_ptr() as *const Inner, s.len())
}
}
/// Convert a mutable slice to the wrapped type into a mutable slice to the
/// inner type.
#[inline]
fn peel_slice_mut(s: &mut [Self]) -> &mut [Inner]
where
Self: Sized,
Inner: Sized,
{
unsafe {
assert!(size_of::<*mut Inner>() == size_of::<*mut Self>());
assert!(align_of::<*mut Inner>() == align_of::<*mut Self>());
// SAFETY: The unsafe contract requires that these two have
// identical representations (size and alignment).
core::slice::from_raw_parts_mut(s.as_mut_ptr() as *mut Inner, s.len())
}
}
}
unsafe impl<T> TransparentWrapper<T> for core::num::Wrapping<T> {}

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use super::*;
/// Trait for types that can be safely created with
/// [`zeroed`](core::mem::zeroed).
///
/// An all-zeroes value may or may not be the same value as the
/// [Default](core::default::Default) value of the type.
///
/// ## Safety
///
/// * Your type must be inhabited (eg: no
/// [Infallible](core::convert::Infallible)).
/// * Your type must be allowed to be an "all zeroes" bit pattern (eg: no
/// [`NonNull<T>`](core::ptr::NonNull)).
///
/// ## Features
///
/// Some `impl`s are feature gated due to the MSRV policy:
///
/// * `MaybeUninit<T>` was not available in 1.34.0, but is available under the
/// `zeroable_maybe_uninit` feature flag.
/// * `Atomic*` types require Rust 1.60.0 or later to work on certain platforms,
/// but is available under the `zeroable_atomics` feature flag.
/// * `[T; N]` for arbitrary `N` requires the `min_const_generics` feature flag.
pub unsafe trait Zeroable: Sized {
/// Calls [`zeroed`](core::mem::zeroed).
///
/// This is a trait method so that you can write `MyType::zeroed()` in your
/// code. It is a contract of this trait that if you implement it on your type
/// you **must not** override this method.
#[inline]
fn zeroed() -> Self {
unsafe { core::mem::zeroed() }
}
}
unsafe impl Zeroable for () {}
unsafe impl Zeroable for bool {}
unsafe impl Zeroable for char {}
unsafe impl Zeroable for u8 {}
unsafe impl Zeroable for i8 {}
unsafe impl Zeroable for u16 {}
unsafe impl Zeroable for i16 {}
unsafe impl Zeroable for u32 {}
unsafe impl Zeroable for i32 {}
unsafe impl Zeroable for u64 {}
unsafe impl Zeroable for i64 {}
unsafe impl Zeroable for usize {}
unsafe impl Zeroable for isize {}
unsafe impl Zeroable for u128 {}
unsafe impl Zeroable for i128 {}
unsafe impl Zeroable for f32 {}
unsafe impl Zeroable for f64 {}
unsafe impl<T: Zeroable> Zeroable for Wrapping<T> {}
unsafe impl<T: Zeroable> Zeroable for core::cmp::Reverse<T> {}
// Note: we can't implement this for all `T: ?Sized` types because it would
// create NULL pointers for vtables.
// Maybe one day this could be changed to be implemented for
// `T: ?Sized where <T as core::ptr::Pointee>::Metadata: Zeroable`.
unsafe impl<T> Zeroable for *mut T {}
unsafe impl<T> Zeroable for *const T {}
unsafe impl<T> Zeroable for *mut [T] {}
unsafe impl<T> Zeroable for *const [T] {}
unsafe impl Zeroable for *mut str {}
unsafe impl Zeroable for *const str {}
unsafe impl<T: ?Sized> Zeroable for PhantomData<T> {}
unsafe impl Zeroable for PhantomPinned {}
unsafe impl<T: Zeroable> Zeroable for ManuallyDrop<T> {}
unsafe impl<T: Zeroable> Zeroable for core::cell::UnsafeCell<T> {}
unsafe impl<T: Zeroable> Zeroable for core::cell::Cell<T> {}
#[cfg(feature = "zeroable_atomics")]
#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "zeroable_atomics")))]
mod atomic_impls {
use super::Zeroable;
#[cfg(target_has_atomic = "8")]
unsafe impl Zeroable for core::sync::atomic::AtomicBool {}
#[cfg(target_has_atomic = "8")]
unsafe impl Zeroable for core::sync::atomic::AtomicU8 {}
#[cfg(target_has_atomic = "8")]
unsafe impl Zeroable for core::sync::atomic::AtomicI8 {}
#[cfg(target_has_atomic = "16")]
unsafe impl Zeroable for core::sync::atomic::AtomicU16 {}
#[cfg(target_has_atomic = "16")]
unsafe impl Zeroable for core::sync::atomic::AtomicI16 {}
#[cfg(target_has_atomic = "32")]
unsafe impl Zeroable for core::sync::atomic::AtomicU32 {}
#[cfg(target_has_atomic = "32")]
unsafe impl Zeroable for core::sync::atomic::AtomicI32 {}
#[cfg(target_has_atomic = "64")]
unsafe impl Zeroable for core::sync::atomic::AtomicU64 {}
#[cfg(target_has_atomic = "64")]
unsafe impl Zeroable for core::sync::atomic::AtomicI64 {}
#[cfg(target_has_atomic = "ptr")]
unsafe impl Zeroable for core::sync::atomic::AtomicUsize {}
#[cfg(target_has_atomic = "ptr")]
unsafe impl Zeroable for core::sync::atomic::AtomicIsize {}
#[cfg(target_has_atomic = "ptr")]
unsafe impl<T> Zeroable for core::sync::atomic::AtomicPtr<T> {}
}
#[cfg(feature = "zeroable_maybe_uninit")]
#[cfg_attr(
feature = "nightly_docs",
doc(cfg(feature = "zeroable_maybe_uninit"))
)]
unsafe impl<T> Zeroable for core::mem::MaybeUninit<T> {}
unsafe impl<A: Zeroable> Zeroable for (A,) {}
unsafe impl<A: Zeroable, B: Zeroable> Zeroable for (A, B) {}
unsafe impl<A: Zeroable, B: Zeroable, C: Zeroable> Zeroable for (A, B, C) {}
unsafe impl<A: Zeroable, B: Zeroable, C: Zeroable, D: Zeroable> Zeroable
for (A, B, C, D)
{
}
unsafe impl<A: Zeroable, B: Zeroable, C: Zeroable, D: Zeroable, E: Zeroable>
Zeroable for (A, B, C, D, E)
{
}
unsafe impl<
A: Zeroable,
B: Zeroable,
C: Zeroable,
D: Zeroable,
E: Zeroable,
F: Zeroable,
> Zeroable for (A, B, C, D, E, F)
{
}
unsafe impl<
A: Zeroable,
B: Zeroable,
C: Zeroable,
D: Zeroable,
E: Zeroable,
F: Zeroable,
G: Zeroable,
> Zeroable for (A, B, C, D, E, F, G)
{
}
unsafe impl<
A: Zeroable,
B: Zeroable,
C: Zeroable,
D: Zeroable,
E: Zeroable,
F: Zeroable,
G: Zeroable,
H: Zeroable,
> Zeroable for (A, B, C, D, E, F, G, H)
{
}
#[cfg(feature = "min_const_generics")]
#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "min_const_generics")))]
unsafe impl<T, const N: usize> Zeroable for [T; N] where T: Zeroable {}
#[cfg(not(feature = "min_const_generics"))]
impl_unsafe_marker_for_array!(
Zeroable, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 48, 64, 96, 128, 256,
512, 1024, 2048, 4096
);
impl_unsafe_marker_for_simd!(
#[cfg(all(target_arch = "wasm32", feature = "wasm_simd"))]
unsafe impl Zeroable for wasm32::{v128}
);
impl_unsafe_marker_for_simd!(
#[cfg(all(target_arch = "aarch64", feature = "aarch64_simd"))]
unsafe impl Zeroable for aarch64::{
float32x2_t, float32x2x2_t, float32x2x3_t, float32x2x4_t, float32x4_t,
float32x4x2_t, float32x4x3_t, float32x4x4_t, float64x1_t, float64x1x2_t,
float64x1x3_t, float64x1x4_t, float64x2_t, float64x2x2_t, float64x2x3_t,
float64x2x4_t, int16x4_t, int16x4x2_t, int16x4x3_t, int16x4x4_t, int16x8_t,
int16x8x2_t, int16x8x3_t, int16x8x4_t, int32x2_t, int32x2x2_t, int32x2x3_t,
int32x2x4_t, int32x4_t, int32x4x2_t, int32x4x3_t, int32x4x4_t, int64x1_t,
int64x1x2_t, int64x1x3_t, int64x1x4_t, int64x2_t, int64x2x2_t, int64x2x3_t,
int64x2x4_t, int8x16_t, int8x16x2_t, int8x16x3_t, int8x16x4_t, int8x8_t,
int8x8x2_t, int8x8x3_t, int8x8x4_t, poly16x4_t, poly16x4x2_t, poly16x4x3_t,
poly16x4x4_t, poly16x8_t, poly16x8x2_t, poly16x8x3_t, poly16x8x4_t,
poly64x1_t, poly64x1x2_t, poly64x1x3_t, poly64x1x4_t, poly64x2_t,
poly64x2x2_t, poly64x2x3_t, poly64x2x4_t, poly8x16_t, poly8x16x2_t,
poly8x16x3_t, poly8x16x4_t, poly8x8_t, poly8x8x2_t, poly8x8x3_t, poly8x8x4_t,
uint16x4_t, uint16x4x2_t, uint16x4x3_t, uint16x4x4_t, uint16x8_t,
uint16x8x2_t, uint16x8x3_t, uint16x8x4_t, uint32x2_t, uint32x2x2_t,
uint32x2x3_t, uint32x2x4_t, uint32x4_t, uint32x4x2_t, uint32x4x3_t,
uint32x4x4_t, uint64x1_t, uint64x1x2_t, uint64x1x3_t, uint64x1x4_t,
uint64x2_t, uint64x2x2_t, uint64x2x3_t, uint64x2x4_t, uint8x16_t,
uint8x16x2_t, uint8x16x3_t, uint8x16x4_t, uint8x8_t, uint8x8x2_t,
uint8x8x3_t, uint8x8x4_t,
}
);
impl_unsafe_marker_for_simd!(
#[cfg(target_arch = "x86")]
unsafe impl Zeroable for x86::{
__m128i, __m128, __m128d,
__m256i, __m256, __m256d,
}
);
impl_unsafe_marker_for_simd!(
#[cfg(target_arch = "x86_64")]
unsafe impl Zeroable for x86_64::{
__m128i, __m128, __m128d,
__m256i, __m256, __m256d,
}
);
#[cfg(feature = "nightly_portable_simd")]
#[cfg_attr(
feature = "nightly_docs",
doc(cfg(feature = "nightly_portable_simd"))
)]
unsafe impl<T, const N: usize> Zeroable for core::simd::Simd<T, N>
where
T: core::simd::SimdElement + Zeroable,
core::simd::LaneCount<N>: core::simd::SupportedLaneCount,
{
}
impl_unsafe_marker_for_simd!(
#[cfg(all(target_arch = "x86", feature = "nightly_stdsimd"))]
unsafe impl Zeroable for x86::{
__m128bh, __m256bh, __m512,
__m512bh, __m512d, __m512i,
}
);
impl_unsafe_marker_for_simd!(
#[cfg(all(target_arch = "x86_64", feature = "nightly_stdsimd"))]
unsafe impl Zeroable for x86_64::{
__m128bh, __m256bh, __m512,
__m512bh, __m512d, __m512i,
}
);

35
vendor/bytemuck/src/zeroable_in_option.rs vendored Normal file
View File

@@ -0,0 +1,35 @@
use super::*;
// Note(Lokathor): This is the neat part!!
unsafe impl<T: ZeroableInOption> Zeroable for Option<T> {}
/// Trait for types which are [Zeroable](Zeroable) when wrapped in
/// [Option](core::option::Option).
///
/// ## Safety
///
/// * `Option<YourType>` must uphold the same invariants as
/// [Zeroable](Zeroable).
pub unsafe trait ZeroableInOption: Sized {}
unsafe impl ZeroableInOption for NonZeroI8 {}
unsafe impl ZeroableInOption for NonZeroI16 {}
unsafe impl ZeroableInOption for NonZeroI32 {}
unsafe impl ZeroableInOption for NonZeroI64 {}
unsafe impl ZeroableInOption for NonZeroI128 {}
unsafe impl ZeroableInOption for NonZeroIsize {}
unsafe impl ZeroableInOption for NonZeroU8 {}
unsafe impl ZeroableInOption for NonZeroU16 {}
unsafe impl ZeroableInOption for NonZeroU32 {}
unsafe impl ZeroableInOption for NonZeroU64 {}
unsafe impl ZeroableInOption for NonZeroU128 {}
unsafe impl ZeroableInOption for NonZeroUsize {}
// Note: this does not create NULL vtable because we get `None` anyway.
unsafe impl<T: ?Sized> ZeroableInOption for NonNull<T> {}
unsafe impl<T: ?Sized> ZeroableInOption for &'_ T {}
unsafe impl<T: ?Sized> ZeroableInOption for &'_ mut T {}
#[cfg(feature = "extern_crate_alloc")]
#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "extern_crate_alloc")))]
unsafe impl<T: ?Sized> ZeroableInOption for alloc::boxed::Box<T> {}