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Lokathor
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commit
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227
src/lib.rs
227
src/lib.rs
@ -3,7 +3,7 @@ pub(crate) use core::arch::x86;
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#[cfg(target_arch = "x86_64")]
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pub(crate) use core::arch::x86_64;
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//
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pub(crate) use core::{marker::*, num::*, ptr::*};
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pub(crate) use core::{marker::*, mem::*, num::*, ptr::*};
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macro_rules! impl_unsafe_marker_for_array {
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( $marker:ident , $( $n:expr ),* ) => {
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@ -11,11 +11,226 @@ macro_rules! impl_unsafe_marker_for_array {
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}
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}
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macro_rules! impl_unsafe_marker_for_type {
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( $marker:ident , $( $t:ty ),* ) => {
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$(unsafe impl<T> $marker for $t {})*
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mod zeroable;
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pub use zeroable::*;
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mod pod;
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pub use pod::*;
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/// Re-interprets `&T` as `&[u8]`.
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///
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/// Any ZST becomes an empty slice, and in that case the pointer value of that
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/// empty slice might not match the pointer value of the input reference.
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#[inline]
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pub fn bytes_of<T: Pod>(t: &T) -> &[u8] {
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try_cast_slice::<T, u8>(core::slice::from_ref(t)).unwrap_or(&[])
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}
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/// Re-interprets `&mut T` as `&mut [u8]`.
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///
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/// Any ZST becomes an empty slice, and in that case the pointer value of that
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/// empty slice might not match the pointer value of the input reference.
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#[inline]
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pub fn bytes_of_mut<T: Pod>(t: &mut T) -> &mut [u8] {
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try_cast_slice_mut::<T, u8>(core::slice::from_mut(t)).unwrap_or(&mut [])
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}
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/// The things that can go wrong when casting between [`Pod`] data forms.
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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pub enum PodCastError {
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/// You tried to cast a slice to an element type with a higher alignment
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/// requirement but the slice wasn't aligned.
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TargetAlignmentGreaterAndInputNotAligned,
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/// You tried to cast between a zero-sized type and a non-zero-sized type.
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/// Because the output slice resizes based on the input and output types, it's
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/// fairly nonsensical to throw a ZST into the mix. You can go from a ZST to
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/// another ZST, if you want.
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CantConvertBetweenZSTAndNonZST,
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/// If the element size changes then the output slice changes length
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/// accordingly. If the output slice wouldn't be a whole number of elements
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/// then the conversion fails.
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OutputSliceWouldHaveSlop,
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/// When casting an individual `T`, `&T`, or `&mut T` value the source size
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/// and destination size must be an exact match.
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SizeMismatch,
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}
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/// Cast `T` into `U`
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///
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/// ## Panics
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///
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/// This is [`try_cast`] with an unwrap.
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#[inline]
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pub fn cast<A: Pod, B: Pod>(a: A) -> B {
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try_cast(a).unwrap()
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}
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/// Cast `&mut T` into `&mut U`.
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///
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/// ## Panics
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///
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/// This is [`try_cast_mut`] with an unwrap.
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#[inline]
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pub fn cast_mut<A: Pod, B: Pod>(a: &mut A) -> &mut B {
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try_cast_mut(a).unwrap()
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}
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/// Cast `&T` into `&U`.
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///
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/// ## Panics
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///
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/// This is [`try_cast_ref`] with an unwrap.
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#[inline]
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pub fn cast_ref<A: Pod, B: Pod>(a: &A) -> &B {
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try_cast_ref(a).unwrap()
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}
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/// Cast `&[T]` into `&[U]`.
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///
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/// ## Panics
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///
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/// This is [`try_cast_slice`] with an unwrap.
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#[inline]
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pub fn cast_slice<A: Pod, B: Pod>(a: &[A]) -> &[B] {
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try_cast_slice(a).unwrap()
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}
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/// Cast `&mut [T]` into `&mut [U]`.
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///
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/// ## Panics
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///
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/// This is [`try_cast_slice_mut`] with an unwrap.
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#[inline]
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pub fn cast_slice_mut<A: Pod, B: Pod>(a: &mut [A]) -> &mut [B] {
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try_cast_slice_mut(a).unwrap()
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}
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/// As `align_to`, but safe because of the [`Pod`] bound.
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#[inline]
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pub fn pod_align_to<T: Pod, U: Pod>(vals: &[T]) -> (&[T], &[U], &[T]) {
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unsafe { vals.align_to::<U>() }
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}
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/// As `align_to_mut`, but safe because of the [`Pod`] bound.
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#[inline]
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pub fn pod_align_to_mut<T: Pod, U: Pod>(vals: &mut [T]) -> (&mut [T], &mut [U], &mut [T]) {
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unsafe { vals.align_to_mut::<U>() }
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}
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/// Try to cast `T` into `U`.
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///
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/// ## Failure
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///
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/// * If the types don't have the same size this fails.
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#[inline]
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pub fn try_cast<A: Pod, B: Pod>(a: A) -> Result<B, PodCastError> {
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if size_of::<A>() == size_of::<B>() {
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let mut b = B::zeroed();
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// Note(Lokathor): We copy in terms of `u8` because that allows us to bypass
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// any potential alignment difficulties.
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let ap = &a as *const A as *const u8;
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let bp = &mut b as *mut B as *mut u8;
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unsafe { ap.copy_to_nonoverlapping(bp, size_of::<A>()) };
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Ok(b)
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} else {
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Err(PodCastError::SizeMismatch)
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}
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}
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mod zeroable;
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pub use zeroable::*;
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/// Try to convert a `&T` into `&U`.
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///
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/// ## Failure
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///
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/// * If the reference isn't aligned in the new type
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/// * If the source type and target type aren't the same size.
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#[inline]
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pub fn try_cast_ref<A: Pod, B: Pod>(a: &A) -> Result<&B, PodCastError> {
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// Note(Lokathor): everything with `align_of` and `size_of` will optimize away
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// after monomorphization.
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if align_of::<B>() > align_of::<A>() && (a as *const A as usize) % align_of::<B>() != 0 {
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Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
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} else if size_of::<B>() == size_of::<A>() {
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Ok(unsafe {
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(a as *const A as *const B)
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.as_ref()
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.unwrap_or_else(|| core::hint::unreachable_unchecked())
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})
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} else {
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Err(PodCastError::SizeMismatch)
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}
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}
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/// Try to convert a `&mut T` into `&mut U`.
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///
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/// As [`try_cast_ref`], but `mut`.
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#[inline]
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pub fn try_cast_mut<A: Pod, B: Pod>(a: &mut A) -> Result<&mut B, PodCastError> {
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// Note(Lokathor): everything with `align_of` and `size_of` will optimize away
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// after monomorphization.
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if align_of::<B>() > align_of::<A>() && (a as *mut A as usize) % align_of::<B>() != 0 {
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Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
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} else if size_of::<B>() == size_of::<A>() {
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Ok(unsafe {
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(a as *mut A as *mut B)
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.as_mut()
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.unwrap_or_else(|| core::hint::unreachable_unchecked())
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})
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} else {
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Err(PodCastError::SizeMismatch)
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}
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}
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/// Try to convert `&[T]` into `&[U]` (possibly with a change in length).
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///
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/// * `input.as_ptr() as usize == output.as_ptr() as usize`
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/// * `input.len() * size_of::<A>() == output.len() * size_of::<B>()`
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///
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/// ## Failure
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///
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/// * If the target type has a greater alignment requirement and the input slice
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/// isn't aligned.
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/// * If the target element type is a different size from the current element
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/// type, and the output slice wouldn't be a whole number of elements when
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/// accounting for the size change (eg: three `u16` values is 1.5 `u32`
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/// values, so that's a failure).
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/// * Similarly, you can't convert between a
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/// [ZST](https://doc.rust-lang.org/nomicon/exotic-sizes.html#zero-sized-types-zsts)
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/// and a non-ZST.
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#[inline]
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pub fn try_cast_slice<A: Pod, B: Pod>(a: &[A]) -> Result<&[B], PodCastError> {
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// Note(Lokathor): everything with `align_of` and `size_of` will optimize away
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// after monomorphization.
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if align_of::<B>() > align_of::<A>() && (a.as_ptr() as usize) % align_of::<B>() != 0 {
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Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
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} else if size_of::<B>() == size_of::<A>() {
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Ok(unsafe { core::slice::from_raw_parts(a.as_ptr() as *const B, a.len()) })
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} else if size_of::<A>() == 0 || size_of::<B>() == 0 {
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Err(PodCastError::CantConvertBetweenZSTAndNonZST)
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} else if core::mem::size_of_val(a) % size_of::<B>() == 0 {
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let new_len = core::mem::size_of_val(a) / size_of::<B>();
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Ok(unsafe { core::slice::from_raw_parts(a.as_ptr() as *const B, new_len) })
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} else {
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Err(PodCastError::OutputSliceWouldHaveSlop)
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}
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}
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/// Try to convert `&mut [T]` into `mut [U]` (possibly with a change in length).
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///
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/// As [`try_cast_slice`], but `mut`.
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#[inline]
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pub fn try_cast_slice_mut<A: Pod, B: Pod>(a: &mut [A]) -> Result<&mut [B], PodCastError> {
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// Note(Lokathor): everything with `align_of` and `size_of` will optimize away
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// after monomorphization.
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if align_of::<B>() > align_of::<A>() && (a.as_ptr() as usize) % align_of::<B>() != 0 {
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Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
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} else if size_of::<B>() == size_of::<A>() {
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Ok(unsafe { core::slice::from_raw_parts_mut(a.as_ptr() as *mut B, a.len()) })
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} else if size_of::<A>() == 0 || size_of::<B>() == 0 {
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Err(PodCastError::CantConvertBetweenZSTAndNonZST)
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} else if core::mem::size_of_val(a) % size_of::<B>() == 0 {
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let new_len = core::mem::size_of_val(a) / size_of::<B>();
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Ok(unsafe { core::slice::from_raw_parts_mut(a.as_ptr() as *mut B, new_len) })
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} else {
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Err(PodCastError::OutputSliceWouldHaveSlop)
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}
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}
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90
src/pod.rs
Normal file
90
src/pod.rs
Normal file
@ -0,0 +1,90 @@
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use super::*;
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/// Marker trait for "plain old data".
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///
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/// The point of this trait is that once something is marked "plain old data"
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/// you can really go to town with the bit fiddling and bit casting. Therefore,
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/// it's a relatively strong claim to make about a type. Do not add this to your
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/// type casually.
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///
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/// **Reminder:** The results of casting around bytes between data types are
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/// _endian dependant_. Little-endian machines are the most common, but
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/// big-endian machines do exist (and big-endian is also used for "network
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/// order" bytes).
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///
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/// ## Safety
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///
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/// * The type must be inhabited (eg: no
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/// [Infallible](core::convert::Infallible)).
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/// * The type must allow any bit pattern (eg: no `bool` or `char`).
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/// * The type must not contain any padding bytes (eg: no `(u8, u16)`).
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/// * A struct needs to be `repr(C)`, or a `repr(transparent)` wrapper around a
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/// `Pod` type.
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pub unsafe trait Pod: Zeroable + Copy + 'static {}
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unsafe impl Pod for () {}
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unsafe impl Pod for u8 {}
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unsafe impl Pod for i8 {}
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unsafe impl Pod for u16 {}
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unsafe impl Pod for i16 {}
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unsafe impl Pod for u32 {}
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unsafe impl Pod for i32 {}
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unsafe impl Pod for u64 {}
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unsafe impl Pod for i64 {}
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unsafe impl Pod for usize {}
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unsafe impl Pod for isize {}
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unsafe impl Pod for u128 {}
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unsafe impl Pod for i128 {}
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unsafe impl Pod for f32 {}
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unsafe impl Pod for f64 {}
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unsafe impl<T: Pod> Pod for Wrapping<T> {}
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unsafe impl Pod for Option<NonZeroI8> {}
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unsafe impl Pod for Option<NonZeroI16> {}
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unsafe impl Pod for Option<NonZeroI32> {}
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unsafe impl Pod for Option<NonZeroI64> {}
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unsafe impl Pod for Option<NonZeroI128> {}
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unsafe impl Pod for Option<NonZeroIsize> {}
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unsafe impl Pod for Option<NonZeroU8> {}
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unsafe impl Pod for Option<NonZeroU16> {}
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unsafe impl Pod for Option<NonZeroU32> {}
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unsafe impl Pod for Option<NonZeroU64> {}
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unsafe impl Pod for Option<NonZeroU128> {}
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unsafe impl Pod for Option<NonZeroUsize> {}
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unsafe impl<T: 'static> Pod for *mut T {}
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unsafe impl<T: 'static> Pod for *const T {}
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unsafe impl<T: 'static> Pod for Option<NonNull<T>> {}
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unsafe impl<T: Pod> Pod for PhantomData<T> {}
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unsafe impl<T: Pod> Pod for ManuallyDrop<T> {}
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impl_unsafe_marker_for_array!(
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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,
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25, 26, 27, 28, 29, 30, 31, 32, 48, 64, 96, 128, 256, 512, 1024
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);
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#[cfg(target_arch = "x86")]
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unsafe impl Pod for x86::__m128i {}
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#[cfg(target_arch = "x86")]
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unsafe impl Pod for x86::__m128 {}
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#[cfg(target_arch = "x86")]
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unsafe impl Pod for x86::__m128d {}
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#[cfg(target_arch = "x86")]
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unsafe impl Pod for x86::__m256i {}
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#[cfg(target_arch = "x86")]
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unsafe impl Pod for x86::__m256 {}
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#[cfg(target_arch = "x86")]
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unsafe impl Pod for x86::__m256d {}
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#[cfg(target_arch = "x86_64")]
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unsafe impl Pod for x86_64::__m128i {}
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#[cfg(target_arch = "x86_64")]
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unsafe impl Pod for x86_64::__m128 {}
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#[cfg(target_arch = "x86_64")]
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unsafe impl Pod for x86_64::__m128d {}
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#[cfg(target_arch = "x86_64")]
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unsafe impl Pod for x86_64::__m256i {}
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#[cfg(target_arch = "x86_64")]
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unsafe impl Pod for x86_64::__m256 {}
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#[cfg(target_arch = "x86_64")]
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unsafe impl Pod for x86_64::__m256d {}
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@ -35,6 +35,7 @@ unsafe impl Zeroable for u128 {}
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unsafe impl Zeroable for i128 {}
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unsafe impl Zeroable for f32 {}
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unsafe impl Zeroable for f64 {}
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unsafe impl<T: Zeroable> Zeroable for Wrapping<T> {}
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unsafe impl Zeroable for Option<NonZeroI8> {}
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unsafe impl Zeroable for Option<NonZeroI16> {}
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@ -52,62 +53,26 @@ unsafe impl Zeroable for Option<NonZeroUsize> {}
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unsafe impl<T> Zeroable for *mut T {}
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unsafe impl<T> Zeroable for *const T {}
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unsafe impl<T> Zeroable for Option<NonNull<T>> {}
|
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unsafe impl<T> Zeroable for PhantomData<T> where T: Zeroable {}
|
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unsafe impl<T: Zeroable> Zeroable for PhantomData<T> {}
|
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unsafe impl<T: Zeroable> Zeroable for ManuallyDrop<T> {}
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unsafe impl<A> Zeroable for (A,) where A: Zeroable {}
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unsafe impl<A, B> Zeroable for (A, B)
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where
|
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A: Zeroable,
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B: Zeroable,
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unsafe impl<A: Zeroable> Zeroable for (A,) {}
|
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unsafe impl<A: Zeroable, B: Zeroable> Zeroable for (A, B) {}
|
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unsafe impl<A: Zeroable, B: Zeroable, C: Zeroable> Zeroable for (A, B, C) {}
|
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unsafe impl<A: Zeroable, B: Zeroable, C: Zeroable, D: Zeroable> Zeroable for (A, B, C, D) {}
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unsafe impl<A: Zeroable, B: Zeroable, C: Zeroable, D: Zeroable, E: Zeroable> Zeroable
|
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for (A, B, C, D, E)
|
||||
{
|
||||
}
|
||||
unsafe impl<A, B, C> Zeroable for (A, B, C)
|
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where
|
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A: Zeroable,
|
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B: Zeroable,
|
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C: Zeroable,
|
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unsafe impl<A: Zeroable, B: Zeroable, C: Zeroable, D: Zeroable, E: Zeroable, F: Zeroable> Zeroable
|
||||
for (A, B, C, D, E, F)
|
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{
|
||||
}
|
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unsafe impl<A, B, C, D> Zeroable for (A, B, C, D)
|
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where
|
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A: Zeroable,
|
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B: Zeroable,
|
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C: Zeroable,
|
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D: Zeroable,
|
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unsafe impl<A: Zeroable, B: Zeroable, C: Zeroable, D: Zeroable, E: Zeroable, F: Zeroable, G: Zeroable>
|
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Zeroable for (A, B, C, D, E, F, G)
|
||||
{
|
||||
}
|
||||
unsafe impl<A, B, C, D, E> Zeroable for (A, B, C, D, E)
|
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where
|
||||
A: Zeroable,
|
||||
B: Zeroable,
|
||||
C: Zeroable,
|
||||
D: Zeroable,
|
||||
E: Zeroable,
|
||||
{
|
||||
}
|
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unsafe impl<A, B, C, D, E, F> Zeroable for (A, B, C, D, E, F)
|
||||
where
|
||||
A: Zeroable,
|
||||
B: Zeroable,
|
||||
C: Zeroable,
|
||||
D: Zeroable,
|
||||
E: Zeroable,
|
||||
F: Zeroable,
|
||||
{
|
||||
}
|
||||
unsafe impl<A, B, C, D, E, F, G> Zeroable for (A, B, C, D, E, F, G)
|
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where
|
||||
A: Zeroable,
|
||||
B: Zeroable,
|
||||
C: Zeroable,
|
||||
D: Zeroable,
|
||||
E: Zeroable,
|
||||
F: Zeroable,
|
||||
G: Zeroable,
|
||||
{
|
||||
}
|
||||
unsafe impl<A, B, C, D, E, F, G, H> Zeroable for (A, B, C, D, E, F, G, H)
|
||||
where
|
||||
unsafe impl<
|
||||
A: Zeroable,
|
||||
B: Zeroable,
|
||||
C: Zeroable,
|
||||
@ -116,6 +81,7 @@ where
|
||||
F: Zeroable,
|
||||
G: Zeroable,
|
||||
H: Zeroable,
|
||||
> Zeroable for (A, B, C, D, E, F, G, H)
|
||||
{
|
||||
}
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user