35 lines
1.8 KiB
Rust
35 lines
1.8 KiB
Rust
//! Trivial, internal byte transmutation.
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//!
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//! A dependency like bytemuck would give us extra assurance of the safety but overall would not
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//! reduce the amount of total unsafety. We don't use it in the interface where the traits would
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//! really become useful.
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//!
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//! SAFETY: These are benign casts as we apply them to fixed size integer types only. All of them
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//! are naturally aligned, valid for all bit patterns and their alignment is surely at most their
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//! size (we assert the latter fact since it is 'implementation defined' if following the letter of
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//! the unsafe code guidelines).
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//!
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//! TODO: Would like to use std-lib here.
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use std::{mem, slice};
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macro_rules! integral_slice_as_bytes{($int:ty, $const:ident $(,$mut:ident)*) => {
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pub(crate) fn $const(slice: &[$int]) -> &[u8] {
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assert!(mem::align_of::<$int>() <= mem::size_of::<$int>());
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unsafe { slice::from_raw_parts(slice.as_ptr() as *const u8, mem::size_of_val(slice)) }
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}
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$(pub(crate) fn $mut(slice: &mut [$int]) -> &mut [u8] {
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assert!(mem::align_of::<$int>() <= mem::size_of::<$int>());
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unsafe { slice::from_raw_parts_mut(slice.as_mut_ptr() as *mut u8, mem::size_of_val(slice)) }
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})*
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}}
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integral_slice_as_bytes!(i8, i8_as_ne_bytes, i8_as_ne_mut_bytes);
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integral_slice_as_bytes!(u16, u16_as_ne_bytes, u16_as_ne_mut_bytes);
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integral_slice_as_bytes!(i16, i16_as_ne_bytes, i16_as_ne_mut_bytes);
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integral_slice_as_bytes!(u32, u32_as_ne_bytes, u32_as_ne_mut_bytes);
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integral_slice_as_bytes!(i32, i32_as_ne_bytes, i32_as_ne_mut_bytes);
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integral_slice_as_bytes!(u64, u64_as_ne_bytes, u64_as_ne_mut_bytes);
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integral_slice_as_bytes!(i64, i64_as_ne_bytes, i64_as_ne_mut_bytes);
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integral_slice_as_bytes!(f32, f32_as_ne_bytes, f32_as_ne_mut_bytes);
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integral_slice_as_bytes!(f64, f64_as_ne_bytes, f64_as_ne_mut_bytes);
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