vendor/byte-tools/src/write_single.rs

   1 use core::{mem, ptr};
   2
   3 macro_rules! write_single {
   4     ($dst:expr, $n:expr, $size:expr, $which:ident) => ({
   5         assert!($size == $dst.len());
   6         unsafe {
   7             let bytes = mem::transmute::<_, [u8; $size]>($n.$which());
   8             ptr::copy_nonoverlapping((&bytes).as_ptr(), $dst.as_mut_ptr(), $size);
   9         }
  10     });
  11 }
  12
  13 /// Write a u32 into a vector, which must be 4 bytes long. The value is written
  14 /// in little-endian format.
  15 #[inline]
  16 pub fn write_u32_le(dst: &mut [u8], n: u32) {
  17     write_single!(dst, n, 4, to_le);
  18 }
  19
  20 /// Write a u32 into a vector, which must be 4 bytes long. The value is written
  21 /// in big-endian format.
  22 #[inline]
  23 pub fn write_u32_be(dst: &mut [u8], n: u32) {
  24     write_single!(dst, n, 4, to_be);
  25 }
  26
  27 /// Write a u64 into a vector, which must be 8 bytes long. The value is written
  28 /// in little-endian format.
  29 #[inline]
  30 pub fn write_u64_le(dst: &mut [u8], n: u64) {
  31     write_single!(dst, n, 8, to_le);
  32 }
  33
  34 /// Write a u64 into a vector, which must be 8 bytes long. The value is written
  35 /// in big-endian format.
  36 #[inline]
  37 pub fn write_u64_be(dst: &mut [u8], n: u64) {
  38     write_single!(dst, n, 8, to_be);
  39 }