Skip to content

Safe implementations of write_uint and write_uint128 #202

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Safe implementations of write_uint and write_uint128 #202

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
37 changes: 9 additions & 28 deletions src/lib.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -73,10 +73,7 @@ cases.
// provokes lots of dead code warnings. So we just squash them.
#![cfg_attr(miri, allow(dead_code, unused_macros))]

use core::{
convert::TryInto, fmt::Debug, hash::Hash, mem::align_of,
ptr::copy_nonoverlapping, slice,
};
use core::{convert::TryInto, fmt::Debug, hash::Hash, mem::align_of, slice};

#[cfg(feature = "std")]
pub use crate::io::{ReadBytesExt, WriteBytesExt};
Expand Down Expand Up @@ -1950,28 +1947,16 @@ impl ByteOrder for BigEndian {
fn write_uint(buf: &mut [u8], n: u64, nbytes: usize) {
assert!(pack_size(n) <= nbytes && nbytes <= 8);
assert!(nbytes <= buf.len());
unsafe {
let bytes = *(&n.to_be() as *const u64 as *const [u8; 8]);
copy_nonoverlapping(
bytes.as_ptr().offset((8 - nbytes) as isize),
buf.as_mut_ptr(),
nbytes,
);
}

buf[..nbytes].copy_from_slice(&n.to_be_bytes()[(8 - nbytes)..]);
}

#[inline]
fn write_uint128(buf: &mut [u8], n: u128, nbytes: usize) {
assert!(pack_size128(n) <= nbytes && nbytes <= 16);
assert!(nbytes <= buf.len());
unsafe {
let bytes = *(&n.to_be() as *const u128 as *const [u8; 16]);
copy_nonoverlapping(
bytes.as_ptr().offset((16 - nbytes) as isize),
buf.as_mut_ptr(),
nbytes,
);
}

buf[..nbytes].copy_from_slice(&n.to_be_bytes()[(16 - nbytes)..]);
}

#[inline]
Expand Down Expand Up @@ -2136,20 +2121,16 @@ impl ByteOrder for LittleEndian {
fn write_uint(buf: &mut [u8], n: u64, nbytes: usize) {
assert!(pack_size(n) <= nbytes && nbytes <= 8);
assert!(nbytes <= buf.len());
unsafe {
let bytes = *(&n.to_le() as *const u64 as *const [u8; 8]);
copy_nonoverlapping(bytes.as_ptr(), buf.as_mut_ptr(), nbytes);
}

buf[..nbytes].copy_from_slice(&n.to_le_bytes()[..nbytes]);
}

#[inline]
fn write_uint128(buf: &mut [u8], n: u128, nbytes: usize) {
assert!(pack_size128(n) <= nbytes && nbytes <= 16);
assert!(nbytes <= buf.len());
unsafe {
let bytes = *(&n.to_le() as *const u128 as *const [u8; 16]);
copy_nonoverlapping(bytes.as_ptr(), buf.as_mut_ptr(), nbytes);
}

buf[..nbytes].copy_from_slice(&n.to_le_bytes()[..nbytes]);
}

#[inline]
Expand Down