| // Copyright 2018 Developers of the Rand project. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| //! Little-Endian utilities |
| //! |
| //! Little-Endian order has been chosen for internal usage; this makes some |
| //! useful functions available. |
| |
| use core::convert::TryInto; |
| |
| /// Reads unsigned 32 bit integers from `src` into `dst`. |
| #[inline] |
| pub fn read_u32_into(src: &[u8], dst: &mut [u32]) { |
| assert!(src.len() >= 4 * dst.len()); |
| for (out, chunk) in dst.iter_mut().zip(src.chunks_exact(4)) { |
| *out = u32::from_le_bytes(chunk.try_into().unwrap()); |
| } |
| } |
| |
| /// Reads unsigned 64 bit integers from `src` into `dst`. |
| #[inline] |
| pub fn read_u64_into(src: &[u8], dst: &mut [u64]) { |
| assert!(src.len() >= 8 * dst.len()); |
| for (out, chunk) in dst.iter_mut().zip(src.chunks_exact(8)) { |
| *out = u64::from_le_bytes(chunk.try_into().unwrap()); |
| } |
| } |
| |
| #[test] |
| fn test_read() { |
| let bytes = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]; |
| |
| let mut buf = [0u32; 4]; |
| read_u32_into(&bytes, &mut buf); |
| assert_eq!(buf[0], 0x04030201); |
| assert_eq!(buf[3], 0x100F0E0D); |
| |
| let mut buf = [0u32; 3]; |
| read_u32_into(&bytes[1..13], &mut buf); // unaligned |
| assert_eq!(buf[0], 0x05040302); |
| assert_eq!(buf[2], 0x0D0C0B0A); |
| |
| let mut buf = [0u64; 2]; |
| read_u64_into(&bytes, &mut buf); |
| assert_eq!(buf[0], 0x0807060504030201); |
| assert_eq!(buf[1], 0x100F0E0D0C0B0A09); |
| |
| let mut buf = [0u64; 1]; |
| read_u64_into(&bytes[7..15], &mut buf); // unaligned |
| assert_eq!(buf[0], 0x0F0E0D0C0B0A0908); |
| } |