Permalink
Fetching contributors…
Cannot retrieve contributors at this time
414 lines (365 sloc) 11.9 KB
// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! An implementation of SipHash.
#![allow(deprecated)]
use marker::PhantomData;
use ptr;
use cmp;
use mem;
/// An implementation of SipHash 1-3.
///
/// This is currently the default hashing function used by standard library
/// (eg. `collections::HashMap` uses it by default).
///
/// See: <https://131002.net/siphash>
#[unstable(feature = "hashmap_internals", issue = "0")]
#[rustc_deprecated(since = "1.13.0",
reason = "use `std::collections::hash_map::DefaultHasher` instead")]
#[derive(Debug, Clone, Default)]
#[doc(hidden)]
pub struct SipHasher13 {
hasher: Hasher<Sip13Rounds>,
}
/// An implementation of SipHash 2-4.
///
/// See: <https://131002.net/siphash/>
#[unstable(feature = "hashmap_internals", issue = "0")]
#[rustc_deprecated(since = "1.13.0",
reason = "use `std::collections::hash_map::DefaultHasher` instead")]
#[derive(Debug, Clone, Default)]
struct SipHasher24 {
hasher: Hasher<Sip24Rounds>,
}
/// An implementation of SipHash 2-4.
///
/// See: <https://131002.net/siphash/>
///
/// SipHash is a general-purpose hashing function: it runs at a good
/// speed (competitive with Spooky and City) and permits strong _keyed_
/// hashing. This lets you key your hashtables from a strong RNG, such as
/// [`rand::os::OsRng`](https://doc.rust-lang.org/rand/rand/os/struct.OsRng.html).
///
/// Although the SipHash algorithm is considered to be generally strong,
/// it is not intended for cryptographic purposes. As such, all
/// cryptographic uses of this implementation are _strongly discouraged_.
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(since = "1.13.0",
reason = "use `std::collections::hash_map::DefaultHasher` instead")]
#[derive(Debug, Clone, Default)]
pub struct SipHasher(SipHasher24);
#[derive(Debug)]
struct Hasher<S: Sip> {
k0: u64,
k1: u64,
length: usize, // how many bytes we've processed
state: State, // hash State
tail: u64, // unprocessed bytes le
ntail: usize, // how many bytes in tail are valid
_marker: PhantomData<S>,
}
#[derive(Debug, Clone, Copy)]
#[repr(C)]
struct State {
// v0, v2 and v1, v3 show up in pairs in the algorithm,
// and simd implementations of SipHash will use vectors
// of v02 and v13. By placing them in this order in the struct,
// the compiler can pick up on just a few simd optimizations by itself.
v0: u64,
v2: u64,
v1: u64,
v3: u64,
}
macro_rules! compress {
($state:expr) => ({
compress!($state.v0, $state.v1, $state.v2, $state.v3)
});
($v0:expr, $v1:expr, $v2:expr, $v3:expr) =>
({
$v0 = $v0.wrapping_add($v1); $v1 = $v1.rotate_left(13); $v1 ^= $v0;
$v0 = $v0.rotate_left(32);
$v2 = $v2.wrapping_add($v3); $v3 = $v3.rotate_left(16); $v3 ^= $v2;
$v0 = $v0.wrapping_add($v3); $v3 = $v3.rotate_left(21); $v3 ^= $v0;
$v2 = $v2.wrapping_add($v1); $v1 = $v1.rotate_left(17); $v1 ^= $v2;
$v2 = $v2.rotate_left(32);
});
}
/// Load an integer of the desired type from a byte stream, in LE order. Uses
/// `copy_nonoverlapping` to let the compiler generate the most efficient way
/// to load it from a possibly unaligned address.
///
/// Unsafe because: unchecked indexing at i..i+size_of(int_ty)
macro_rules! load_int_le {
($buf:expr, $i:expr, $int_ty:ident) =>
({
debug_assert!($i + mem::size_of::<$int_ty>() <= $buf.len());
let mut data = 0 as $int_ty;
ptr::copy_nonoverlapping($buf.get_unchecked($i),
&mut data as *mut _ as *mut u8,
mem::size_of::<$int_ty>());
data.to_le()
});
}
/// Load an u64 using up to 7 bytes of a byte slice.
///
/// Unsafe because: unchecked indexing at start..start+len
#[inline]
unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
debug_assert!(len < 8);
let mut i = 0; // current byte index (from LSB) in the output u64
let mut out = 0;
if i + 3 < len {
out = load_int_le!(buf, start + i, u32) as u64;
i += 4;
}
if i + 1 < len {
out |= (load_int_le!(buf, start + i, u16) as u64) << (i * 8);
i += 2
}
if i < len {
out |= (*buf.get_unchecked(start + i) as u64) << (i * 8);
i += 1;
}
debug_assert_eq!(i, len);
out
}
impl SipHasher {
/// Creates a new `SipHasher` with the two initial keys set to 0.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(since = "1.13.0",
reason = "use `std::collections::hash_map::DefaultHasher` instead")]
pub fn new() -> SipHasher {
SipHasher::new_with_keys(0, 0)
}
/// Creates a `SipHasher` that is keyed off the provided keys.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_deprecated(since = "1.13.0",
reason = "use `std::collections::hash_map::DefaultHasher` instead")]
pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher {
SipHasher(SipHasher24 {
hasher: Hasher::new_with_keys(key0, key1)
})
}
}
impl SipHasher13 {
/// Creates a new `SipHasher13` with the two initial keys set to 0.
#[inline]
#[unstable(feature = "hashmap_internals", issue = "0")]
#[rustc_deprecated(since = "1.13.0",
reason = "use `std::collections::hash_map::DefaultHasher` instead")]
pub fn new() -> SipHasher13 {
SipHasher13::new_with_keys(0, 0)
}
/// Creates a `SipHasher13` that is keyed off the provided keys.
#[inline]
#[unstable(feature = "hashmap_internals", issue = "0")]
#[rustc_deprecated(since = "1.13.0",
reason = "use `std::collections::hash_map::DefaultHasher` instead")]
pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher13 {
SipHasher13 {
hasher: Hasher::new_with_keys(key0, key1)
}
}
}
impl<S: Sip> Hasher<S> {
#[inline]
fn new_with_keys(key0: u64, key1: u64) -> Hasher<S> {
let mut state = Hasher {
k0: key0,
k1: key1,
length: 0,
state: State {
v0: 0,
v1: 0,
v2: 0,
v3: 0,
},
tail: 0,
ntail: 0,
_marker: PhantomData,
};
state.reset();
state
}
#[inline]
fn reset(&mut self) {
self.length = 0;
self.state.v0 = self.k0 ^ 0x736f6d6570736575;
self.state.v1 = self.k1 ^ 0x646f72616e646f6d;
self.state.v2 = self.k0 ^ 0x6c7967656e657261;
self.state.v3 = self.k1 ^ 0x7465646279746573;
self.ntail = 0;
}
// Specialized write function that is only valid for buffers with len <= 8.
// It's used to force inlining of write_u8 and write_usize, those would normally be inlined
// except for composite types (that includes slices and str hashing because of delimiter).
// Without this extra push the compiler is very reluctant to inline delimiter writes,
// degrading performance substantially for the most common use cases.
#[inline]
fn short_write(&mut self, msg: &[u8]) {
debug_assert!(msg.len() <= 8);
let length = msg.len();
self.length += length;
let needed = 8 - self.ntail;
let fill = cmp::min(length, needed);
if fill == 8 {
self.tail = unsafe { load_int_le!(msg, 0, u64) };
} else {
self.tail |= unsafe { u8to64_le(msg, 0, fill) } << (8 * self.ntail);
if length < needed {
self.ntail += length;
return;
}
}
self.state.v3 ^= self.tail;
S::c_rounds(&mut self.state);
self.state.v0 ^= self.tail;
// Buffered tail is now flushed, process new input.
self.ntail = length - needed;
self.tail = unsafe { u8to64_le(msg, needed, self.ntail) };
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl super::Hasher for SipHasher {
#[inline]
fn write(&mut self, msg: &[u8]) {
self.0.hasher.write(msg)
}
#[inline]
fn finish(&self) -> u64 {
self.0.hasher.finish()
}
}
#[unstable(feature = "hashmap_internals", issue = "0")]
impl super::Hasher for SipHasher13 {
#[inline]
fn write(&mut self, msg: &[u8]) {
self.hasher.write(msg)
}
#[inline]
fn finish(&self) -> u64 {
self.hasher.finish()
}
}
impl<S: Sip> super::Hasher for Hasher<S> {
// see short_write comment for explanation
#[inline]
fn write_usize(&mut self, i: usize) {
let bytes = unsafe {
::slice::from_raw_parts(&i as *const usize as *const u8, mem::size_of::<usize>())
};
self.short_write(bytes);
}
// see short_write comment for explanation
#[inline]
fn write_u8(&mut self, i: u8) {
self.short_write(&[i]);
}
#[inline]
fn write(&mut self, msg: &[u8]) {
let length = msg.len();
self.length += length;
let mut needed = 0;
if self.ntail != 0 {
needed = 8 - self.ntail;
self.tail |= unsafe { u8to64_le(msg, 0, cmp::min(length, needed)) } << 8 * self.ntail;
if length < needed {
self.ntail += length;
return
} else {
self.state.v3 ^= self.tail;
S::c_rounds(&mut self.state);
self.state.v0 ^= self.tail;
self.ntail = 0;
}
}
// Buffered tail is now flushed, process new input.
let len = length - needed;
let left = len & 0x7;
let mut i = needed;
while i < len - left {
let mi = unsafe { load_int_le!(msg, i, u64) };
self.state.v3 ^= mi;
S::c_rounds(&mut self.state);
self.state.v0 ^= mi;
i += 8;
}
self.tail = unsafe { u8to64_le(msg, i, left) };
self.ntail = left;
}
#[inline]
fn finish(&self) -> u64 {
let mut state = self.state;
let b: u64 = ((self.length as u64 & 0xff) << 56) | self.tail;
state.v3 ^= b;
S::c_rounds(&mut state);
state.v0 ^= b;
state.v2 ^= 0xff;
S::d_rounds(&mut state);
state.v0 ^ state.v1 ^ state.v2 ^ state.v3
}
}
impl<S: Sip> Clone for Hasher<S> {
#[inline]
fn clone(&self) -> Hasher<S> {
Hasher {
k0: self.k0,
k1: self.k1,
length: self.length,
state: self.state,
tail: self.tail,
ntail: self.ntail,
_marker: self._marker,
}
}
}
impl<S: Sip> Default for Hasher<S> {
/// Creates a `Hasher<S>` with the two initial keys set to 0.
#[inline]
fn default() -> Hasher<S> {
Hasher::new_with_keys(0, 0)
}
}
#[doc(hidden)]
trait Sip {
fn c_rounds(_: &mut State);
fn d_rounds(_: &mut State);
}
#[derive(Debug, Clone, Default)]
struct Sip13Rounds;
impl Sip for Sip13Rounds {
#[inline]
fn c_rounds(state: &mut State) {
compress!(state);
}
#[inline]
fn d_rounds(state: &mut State) {
compress!(state);
compress!(state);
compress!(state);
}
}
#[derive(Debug, Clone, Default)]
struct Sip24Rounds;
impl Sip for Sip24Rounds {
#[inline]
fn c_rounds(state: &mut State) {
compress!(state);
compress!(state);
}
#[inline]
fn d_rounds(state: &mut State) {
compress!(state);
compress!(state);
compress!(state);
compress!(state);
}
}