69 lines
2.0 KiB
Rust
69 lines
2.0 KiB
Rust
// Copyright 2018 Developers of the Rand project.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Little-Endian utilities
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//!
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//! Little-Endian order has been chosen for internal usage; this makes some
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//! useful functions available.
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use core::ptr;
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macro_rules! read_slice {
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($src:expr, $dst:expr, $size:expr, $which:ident) => {{
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assert_eq!($src.len(), $size * $dst.len());
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unsafe {
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ptr::copy_nonoverlapping(
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$src.as_ptr(),
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$dst.as_mut_ptr() as *mut u8,
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$src.len());
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}
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for v in $dst.iter_mut() {
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*v = v.$which();
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}
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}};
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}
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/// Reads unsigned 32 bit integers from `src` into `dst`.
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/// Borrowed from the `byteorder` crate.
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#[inline]
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pub fn read_u32_into(src: &[u8], dst: &mut [u32]) {
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read_slice!(src, dst, 4, to_le);
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}
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/// Reads unsigned 64 bit integers from `src` into `dst`.
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/// Borrowed from the `byteorder` crate.
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#[inline]
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pub fn read_u64_into(src: &[u8], dst: &mut [u64]) {
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read_slice!(src, dst, 8, to_le);
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}
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#[test]
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fn test_read() {
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let bytes = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
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let mut buf = [0u32; 4];
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read_u32_into(&bytes, &mut buf);
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assert_eq!(buf[0], 0x04030201);
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assert_eq!(buf[3], 0x100F0E0D);
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let mut buf = [0u32; 3];
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read_u32_into(&bytes[1..13], &mut buf); // unaligned
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assert_eq!(buf[0], 0x05040302);
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assert_eq!(buf[2], 0x0D0C0B0A);
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let mut buf = [0u64; 2];
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read_u64_into(&bytes, &mut buf);
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assert_eq!(buf[0], 0x0807060504030201);
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assert_eq!(buf[1], 0x100F0E0D0C0B0A09);
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let mut buf = [0u64; 1];
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read_u64_into(&bytes[7..15], &mut buf); // unaligned
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assert_eq!(buf[0], 0x0F0E0D0C0B0A0908);
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}
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