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    // 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::ptr;

    macro_rules! read_slice {
        ($src:expr, $dst:expr, $size:expr, $which:ident) => {{
            assert_eq!($src.len(), $size * $dst.len());

            unsafe {
                ptr::copy_nonoverlapping(
                    $src.as_ptr(),
                    $dst.as_mut_ptr() as *mut u8,
                    $src.len());
            }
            for v in $dst.iter_mut() {
                *v = v.$which();
            }
        }};
    }

    /// Reads unsigned 32 bit integers from `src` into `dst`.
    /// Borrowed from the `byteorder` crate.
    #[inline]
    pub fn read_u32_into(src: &[u8], dst: &mut [u32]) {
        read_slice!(src, dst, 4, to_le);
    }

    /// Reads unsigned 64 bit integers from `src` into `dst`.
    /// Borrowed from the `byteorder` crate.
    #[inline]
    pub fn read_u64_into(src: &[u8], dst: &mut [u64]) {
        read_slice!(src, dst, 8, to_le);
    }

    #[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);
    }

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