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Eliminate unsafe_write_num_bytes and thus unsafe block inside of it #193

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Eliminate unsafe_write_num_bytes and thus unsafe block inside of it #193

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33 changes: 8 additions & 25 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1895,23 +1895,6 @@ pub type NativeEndian = LittleEndian;
#[cfg(target_endian = "big")]
pub type NativeEndian = BigEndian;

/// Copies $size bytes from a number $n to a &mut [u8] $dst. $ty represents the
/// numeric type of $n and $which must be either to_be or to_le, depending on
/// which endianness one wants to use when writing to $dst.
///
/// This macro is only safe to call when $ty is a numeric type and $size ==
/// size_of::<$ty>() and where $dst is a &mut [u8].
macro_rules! unsafe_write_num_bytes {
($ty:ty, $size:expr, $n:expr, $dst:expr, $which:ident) => {{
assert!($size <= $dst.len());
unsafe {
// N.B. https://github.com/rust-lang/rust/issues/22776
let bytes = *(&$n.$which() as *const _ as *const [u8; $size]);
copy_nonoverlapping((&bytes).as_ptr(), $dst.as_mut_ptr(), $size);
}
}};
}

/// Copies a &[u8] $src into a &mut [<numeric>] $dst for the endianness given
/// by $which (must be either to_be or to_le).
///
Expand Down Expand Up @@ -2020,22 +2003,22 @@ impl ByteOrder for BigEndian {

#[inline]
fn write_u16(buf: &mut [u8], n: u16) {
unsafe_write_num_bytes!(u16, 2, n, buf, to_be);
buf[..2].copy_from_slice(&n.to_be_bytes());
}

#[inline]
fn write_u32(buf: &mut [u8], n: u32) {
unsafe_write_num_bytes!(u32, 4, n, buf, to_be);
buf[..4].copy_from_slice(&n.to_be_bytes());
}

#[inline]
fn write_u64(buf: &mut [u8], n: u64) {
unsafe_write_num_bytes!(u64, 8, n, buf, to_be);
buf[..8].copy_from_slice(&n.to_be_bytes());
}

#[inline]
fn write_u128(buf: &mut [u8], n: u128) {
unsafe_write_num_bytes!(u128, 16, n, buf, to_be);
buf[..16].copy_from_slice(&n.to_be_bytes());
}

#[inline]
Expand Down Expand Up @@ -2228,22 +2211,22 @@ impl ByteOrder for LittleEndian {

#[inline]
fn write_u16(buf: &mut [u8], n: u16) {
unsafe_write_num_bytes!(u16, 2, n, buf, to_le);
buf[..2].copy_from_slice(&n.to_le_bytes());
}

#[inline]
fn write_u32(buf: &mut [u8], n: u32) {
unsafe_write_num_bytes!(u32, 4, n, buf, to_le);
buf[..4].copy_from_slice(&n.to_le_bytes());
}

#[inline]
fn write_u64(buf: &mut [u8], n: u64) {
unsafe_write_num_bytes!(u64, 8, n, buf, to_le);
buf[..8].copy_from_slice(&n.to_le_bytes());
}

#[inline]
fn write_u128(buf: &mut [u8], n: u128) {
unsafe_write_num_bytes!(u128, 16, n, buf, to_le);
buf[..16].copy_from_slice(&n.to_le_bytes());
}

#[inline]
Expand Down