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reduce unsafe (#1972)

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fakeshadow 2021-02-10 15:11:12 -08:00 committed by GitHub
parent ea5ce3befb
commit d9d0d1d1a2
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3 changed files with 77 additions and 131 deletions
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7
actix-http/src/h1/dispatcher.rs
View File

@ -309,11 +309,8 @@ where
}
}
// SAFETY: setting length to 0 is safe
// skips one length check vs truncate
unsafe {
write_buf.set_len(0);
}
// everything has written to io. clear buffer.
write_buf.clear();
// flush the io and check if get blocked.
let blocked = io.poll_flush(cx)?.is_pending();

12
actix-http/src/ws/frame.rs
View File

@ -16,7 +16,8 @@ impl Parser {
src: &[u8],
server: bool,
max_size: usize,
) -> Result<Option<(usize, bool, OpCode, usize, Option<u32>)>, ProtocolError> {
) -> Result<Option<(usize, bool, OpCode, usize, Option<[u8; 4]>)>, ProtocolError>
{
let chunk_len = src.len();
let mut idx = 2;
@ -77,9 +78,10 @@ impl Parser {
return Ok(None);
}
let mask =
u32::from_le_bytes(TryFrom::try_from(&src[idx..idx + 4]).unwrap());
let mask = TryFrom::try_from(&src[idx..idx + 4]).unwrap();
idx += 4;
Some(mask)
} else {
None
@ -187,8 +189,8 @@ impl Parser {
};
if mask {
let mask = rand::random::<u32>();
dst.put_u32_le(mask);
let mask = rand::random::<[u8; 4]>();
dst.put_slice(mask.as_ref());
dst.put_slice(payload.as_ref());
let pos = dst.len() - payload_len;
apply_mask(&mut dst[pos..], mask);

189
actix-http/src/ws/mask.rs
View File

@ -1,136 +1,57 @@
//! This is code from [Tungstenite project](https://github.com/snapview/tungstenite-rs)
#![allow(clippy::cast_ptr_alignment)]
use std::ptr::copy_nonoverlapping;
use std::slice;
/// Holds a slice guaranteed to be shorter than 8 bytes.
struct ShortSlice<'a> {
inner: &'a mut [u8],
}
impl<'a> ShortSlice<'a> {
/// # Safety
/// Given slice must be shorter than 8 bytes.
unsafe fn new(slice: &'a mut [u8]) -> Self {
// Sanity check for debug builds
debug_assert!(slice.len() < 8);
ShortSlice { inner: slice }
}
fn len(&self) -> usize {
self.inner.len()
}
}
/// Faster version of `apply_mask()` which operates on 8-byte blocks.
/// Mask/unmask a frame.
#[inline]
#[allow(clippy::cast_lossless)]
pub(crate) fn apply_mask(buf: &mut [u8], mask_u32: u32) {
// Extend the mask to 64 bits
let mut mask_u64 = ((mask_u32 as u64) << 32) | (mask_u32 as u64);
// Split the buffer into three segments
let (head, mid, tail) = align_buf(buf);
pub fn apply_mask(buf: &mut [u8], mask: [u8; 4]) {
apply_mask_fast32(buf, mask)
}
// Initial unaligned segment
let head_len = head.len();
if head_len > 0 {
xor_short(head, mask_u64);
/// A safe unoptimized mask application.
#[inline]
fn apply_mask_fallback(buf: &mut [u8], mask: [u8; 4]) {
for (i, byte) in buf.iter_mut().enumerate() {
*byte ^= mask[i & 3];
}
}
/// Faster version of `apply_mask()` which operates on 4-byte blocks.
#[inline]
pub fn apply_mask_fast32(buf: &mut [u8], mask: [u8; 4]) {
let mask_u32 = u32::from_ne_bytes(mask);
// SAFETY:
//
// buf is a valid slice borrowed mutably from bytes::BytesMut.
//
// un aligned prefix and suffix would be mask/unmask per byte.
// proper aligned middle slice goes into fast path and operates on 4-byte blocks.
let (mut prefix, words, mut suffix) = unsafe { buf.align_to_mut::<u32>() };
apply_mask_fallback(&mut prefix, mask);
let head = prefix.len() & 3;
let mask_u32 = if head > 0 {
if cfg!(target_endian = "big") {
mask_u64 = mask_u64.rotate_left(8 * head_len as u32);
mask_u32.rotate_left(8 * head as u32)
} else {
mask_u64 = mask_u64.rotate_right(8 * head_len as u32);
}
}
// Aligned segment
for v in mid {
*v ^= mask_u64;
}
// Final unaligned segment
if tail.len() > 0 {
xor_short(tail, mask_u64);
}
}
// TODO: copy_nonoverlapping here compiles to call memcpy. While it is not so
// inefficient, it could be done better. The compiler does not understand that
// a `ShortSlice` must be smaller than a u64.
#[inline]
#[allow(clippy::needless_pass_by_value)]
fn xor_short(buf: ShortSlice<'_>, mask: u64) {
// SAFETY: we know that a `ShortSlice` fits in a u64
unsafe {
let (ptr, len) = (buf.inner.as_mut_ptr(), buf.len());
let mut b: u64 = 0;
#[allow(trivial_casts)]
copy_nonoverlapping(ptr, &mut b as *mut _ as *mut u8, len);
b ^= mask;
#[allow(trivial_casts)]
copy_nonoverlapping(&b as *const _ as *const u8, ptr, len);
}
}
/// # Safety
/// Caller must ensure the buffer has the correct size and alignment.
#[inline]
unsafe fn cast_slice(buf: &mut [u8]) -> &mut [u64] {
// Assert correct size and alignment in debug builds
debug_assert!(buf.len().trailing_zeros() >= 3);
debug_assert!((buf.as_ptr() as usize).trailing_zeros() >= 3);
slice::from_raw_parts_mut(buf.as_mut_ptr() as *mut u64, buf.len() >> 3)
}
/// Splits a slice into three parts:
/// - an unaligned short head
/// - an aligned `u64` slice mid section
/// - an unaligned short tail
#[inline]
fn align_buf(buf: &mut [u8]) -> (ShortSlice<'_>, &mut [u64], ShortSlice<'_>) {
let start_ptr = buf.as_ptr() as usize;
let end_ptr = start_ptr + buf.len();
// Round *up* to next aligned boundary for start
let start_aligned = (start_ptr + 7) & !0x7;
// Round *down* to last aligned boundary for end
let end_aligned = end_ptr & !0x7;
if end_aligned >= start_aligned {
// We have our three segments (head, mid, tail)
let (tmp, tail) = buf.split_at_mut(end_aligned - start_ptr);
let (head, mid) = tmp.split_at_mut(start_aligned - start_ptr);
// SAFETY: we know the middle section is correctly aligned, and the outer
// sections are smaller than 8 bytes
unsafe {
(
ShortSlice::new(head),
cast_slice(mid),
ShortSlice::new(tail),
)
mask_u32.rotate_right(8 * head as u32)
}
} else {
// We didn't cross even one aligned boundary!
// SAFETY: The outer sections are smaller than 8 bytes
unsafe { (ShortSlice::new(buf), &mut [], ShortSlice::new(&mut [])) }
mask_u32
};
for word in words.iter_mut() {
*word ^= mask_u32;
}
apply_mask_fallback(&mut suffix, mask_u32.to_ne_bytes());
}
#[cfg(test)]
mod tests {
use super::apply_mask;
/// A safe unoptimized mask application.
fn apply_mask_fallback(buf: &mut [u8], mask: &[u8; 4]) {
for (i, byte) in buf.iter_mut().enumerate() {
*byte ^= mask[i & 3];
}
}
use super::*;
// legacy test from old apply mask test. kept for now for back compat test.
// TODO: remove it and favor the other test.
#[test]
fn test_apply_mask() {
fn test_apply_mask_legacy() {
let mask = [0x6d, 0xb6, 0xb2, 0x80];
let mask_u32 = u32::from_le_bytes(mask);
let unmasked = vec![
0xf3, 0x00, 0x01, 0x02, 0x03, 0x80, 0x81, 0x82, 0xff, 0xfe, 0x00, 0x17,
@ -140,10 +61,10 @@ mod tests {
// Check masking with proper alignment.
{
let mut masked = unmasked.clone();
apply_mask_fallback(&mut masked, &mask);
apply_mask_fallback(&mut masked, mask);
let mut masked_fast = unmasked.clone();
apply_mask(&mut masked_fast, mask_u32);
apply_mask(&mut masked_fast, mask);
assert_eq!(masked, masked_fast);
}
@ -151,12 +72,38 @@ mod tests {
// Check masking without alignment.
{
let mut masked = unmasked.clone();
apply_mask_fallback(&mut masked[1..], &mask);
apply_mask_fallback(&mut masked[1..], mask);
let mut masked_fast = unmasked;
apply_mask(&mut masked_fast[1..], mask_u32);
apply_mask(&mut masked_fast[1..], mask);
assert_eq!(masked, masked_fast);
}
}
#[test]
fn test_apply_mask() {
let mask = [0x6d, 0xb6, 0xb2, 0x80];
let unmasked = vec![
0xf3, 0x00, 0x01, 0x02, 0x03, 0x80, 0x81, 0x82, 0xff, 0xfe, 0x00, 0x17,
0x74, 0xf9, 0x12, 0x03,
];
for data_len in 0..=unmasked.len() {
let unmasked = &unmasked[0..data_len];
// Check masking with different alignment.
for off in 0..=3 {
if unmasked.len() < off {
continue;
}
let mut masked = unmasked.to_vec();
apply_mask_fallback(&mut masked[off..], mask);
let mut masked_fast = unmasked.to_vec();
apply_mask_fast32(&mut masked_fast[off..], mask);
assert_eq!(masked, masked_fast);
}
}
}
}