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Use const generics in SipHasher128's short_write

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Jakub Beránek 2022-02-04 16:26:36 +01:00
parent 4c55c8362d
commit 5fc2e5623b
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2 changed files with 39 additions and 46 deletions
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61
compiler/rustc_data_structures/src/sip128.rs
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@ -202,28 +202,26 @@ impl SipHasher128 {
hasher
}
// A specialized write function for values with size <= 8.
#[inline]
fn short_write<T>(&mut self, x: T) {
let size = mem::size_of::<T>();
pub fn short_write<const LEN: usize>(&mut self, bytes: [u8; LEN]) {
let nbuf = self.nbuf;
debug_assert!(size <= 8);
debug_assert!(LEN <= 8);
debug_assert!(nbuf < BUFFER_SIZE);
debug_assert!(nbuf + size < BUFFER_WITH_SPILL_SIZE);
debug_assert!(nbuf + LEN < BUFFER_WITH_SPILL_SIZE);
if nbuf + size < BUFFER_SIZE {
if nbuf + LEN < BUFFER_SIZE {
unsafe {
// The memcpy call is optimized away because the size is known.
let dst = (self.buf.as_mut_ptr() as *mut u8).add(nbuf);
ptr::copy_nonoverlapping(&x as *const _ as *const u8, dst, size);
ptr::copy_nonoverlapping(bytes.as_ptr(), dst, LEN);
}
self.nbuf = nbuf + size;
self.nbuf = nbuf + LEN;
return;
}
unsafe { self.short_write_process_buffer(x) }
unsafe { self.short_write_process_buffer(bytes) }
}
// A specialized write function for values with size <= 8 that should only
@ -233,18 +231,17 @@ impl SipHasher128 {
// `self.nbuf` must cause `self.buf` to become fully initialized (and not
// overflow) if it wasn't already.
#[inline(never)]
unsafe fn short_write_process_buffer<T>(&mut self, x: T) {
let size = mem::size_of::<T>();
unsafe fn short_write_process_buffer<const LEN: usize>(&mut self, bytes: [u8; LEN]) {
let nbuf = self.nbuf;
debug_assert!(size <= 8);
debug_assert!(LEN <= 8);
debug_assert!(nbuf < BUFFER_SIZE);
debug_assert!(nbuf + size >= BUFFER_SIZE);
debug_assert!(nbuf + size < BUFFER_WITH_SPILL_SIZE);
debug_assert!(nbuf + LEN >= BUFFER_SIZE);
debug_assert!(nbuf + LEN < BUFFER_WITH_SPILL_SIZE);
// Copy first part of input into end of buffer, possibly into spill
// element. The memcpy call is optimized away because the size is known.
let dst = (self.buf.as_mut_ptr() as *mut u8).add(nbuf);
ptr::copy_nonoverlapping(&x as *const _ as *const u8, dst, size);
ptr::copy_nonoverlapping(bytes.as_ptr(), dst, LEN);
// Process buffer.
for i in 0..BUFFER_CAPACITY {
@ -254,17 +251,17 @@ impl SipHasher128 {
self.state.v0 ^= elem;
}
// Copy remaining input into start of buffer by copying size - 1
// elements from spill (at most size - 1 bytes could have overflowed
// Copy remaining input into start of buffer by copying LEN - 1
// elements from spill (at most LEN - 1 bytes could have overflowed
// into the spill). The memcpy call is optimized away because the size
// is known. And the whole copy is optimized away for size == 1.
// is known. And the whole copy is optimized away for LEN == 1.
let src = self.buf.get_unchecked(BUFFER_SPILL_INDEX) as *const _ as *const u8;
ptr::copy_nonoverlapping(src, self.buf.as_mut_ptr() as *mut u8, size - 1);
ptr::copy_nonoverlapping(src, self.buf.as_mut_ptr() as *mut u8, LEN - 1);
// This function should only be called when the write fills the buffer.
// Therefore, when size == 1, the new `self.nbuf` must be zero. The size
// is statically known, so the branch is optimized away.
self.nbuf = if size == 1 { 0 } else { nbuf + size - BUFFER_SIZE };
// Therefore, when LEN == 1, the new `self.nbuf` must be zero.
// LEN is statically known, so the branch is optimized away.
self.nbuf = if LEN == 1 { 0 } else { nbuf + LEN - BUFFER_SIZE };
self.processed += BUFFER_SIZE;
}
@ -412,52 +409,52 @@ impl SipHasher128 {
impl Hasher for SipHasher128 {
#[inline]
fn write_u8(&mut self, i: u8) {
self.short_write(i);
self.short_write(i.to_ne_bytes());
}
#[inline]
fn write_u16(&mut self, i: u16) {
self.short_write(i);
self.short_write(i.to_ne_bytes());
}
#[inline]
fn write_u32(&mut self, i: u32) {
self.short_write(i);
self.short_write(i.to_ne_bytes());
}
#[inline]
fn write_u64(&mut self, i: u64) {
self.short_write(i);
self.short_write(i.to_ne_bytes());
}
#[inline]
fn write_usize(&mut self, i: usize) {
self.short_write(i);
self.short_write(i.to_ne_bytes());
}
#[inline]
fn write_i8(&mut self, i: i8) {
self.short_write(i as u8);
self.short_write((i as u8).to_ne_bytes());
}
#[inline]
fn write_i16(&mut self, i: i16) {
self.short_write(i as u16);
self.short_write((i as u16).to_ne_bytes());
}
#[inline]
fn write_i32(&mut self, i: i32) {
self.short_write(i as u32);
self.short_write((i as u32).to_ne_bytes());
}
#[inline]
fn write_i64(&mut self, i: i64) {
self.short_write(i as u64);
self.short_write((i as u64).to_ne_bytes());
}
#[inline]
fn write_isize(&mut self, i: isize) {
self.short_write(i as usize);
self.short_write((i as usize).to_ne_bytes());
}
#[inline]