src/libcore/hash/sip.rs

   1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! An implementation of SipHash 2-4.
  12
  13 #![allow(deprecated)] // until the next snapshot for inherent wrapping ops
  14
  15 use prelude::*;
  16 use super::Hasher;
  17
  18 /// An implementation of SipHash 2-4.
  19 ///
  20 /// See: http://131002.net/siphash/
  21 ///
  22 /// Consider this as a main "general-purpose" hash for all hashtables: it
  23 /// runs at good speed (competitive with spooky and city) and permits
  24 /// strong _keyed_ hashing. Key your hashtables from a strong RNG,
  25 /// such as `rand::Rng`.
  26 ///
  27 /// Although the SipHash algorithm is considered to be cryptographically
  28 /// strong, this implementation has not been reviewed for such purposes.
  29 /// As such, all cryptographic uses of this implementation are strongly
  30 /// discouraged.
  31 #[stable(feature = "rust1", since = "1.0.0")]
  32 pub struct SipHasher {
  33     k0: u64,
  34     k1: u64,
  35     length: usize, // how many bytes we've processed
  36     v0: u64,      // hash state
  37     v1: u64,
  38     v2: u64,
  39     v3: u64,
  40     tail: u64, // unprocessed bytes le
  41     ntail: usize,  // how many bytes in tail are valid
  42 }
  43
  44 // sadly, these macro definitions can't appear later,
  45 // because they're needed in the following defs;
  46 // this design could be improved.
  47
  48 macro_rules! u8to64_le {
  49     ($buf:expr, $i:expr) =>
  50     ($buf[0+$i] as u64 |
  51      ($buf[1+$i] as u64) << 8 |
  52      ($buf[2+$i] as u64) << 16 |
  53      ($buf[3+$i] as u64) << 24 |
  54      ($buf[4+$i] as u64) << 32 |
  55      ($buf[5+$i] as u64) << 40 |
  56      ($buf[6+$i] as u64) << 48 |
  57      ($buf[7+$i] as u64) << 56);
  58     ($buf:expr, $i:expr, $len:expr) =>
  59     ({
  60         let mut t = 0;
  61         let mut out = 0;
  62         while t < $len {
  63             out |= ($buf[t+$i] as u64) << t*8;
  64             t += 1;
  65         }
  66         out
  67     });
  68 }
  69
  70 macro_rules! rotl {
  71     ($x:expr, $b:expr) =>
  72     (($x << $b) | ($x >> (64_i32.wrapping_sub($b))))
  73 }
  74
  75 macro_rules! compress {
  76     ($v0:expr, $v1:expr, $v2:expr, $v3:expr) =>
  77     ({
  78         $v0 = $v0.wrapping_add($v1); $v1 = rotl!($v1, 13); $v1 ^= $v0;
  79         $v0 = rotl!($v0, 32);
  80         $v2 = $v2.wrapping_add($v3); $v3 = rotl!($v3, 16); $v3 ^= $v2;
  81         $v0 = $v0.wrapping_add($v3); $v3 = rotl!($v3, 21); $v3 ^= $v0;
  82         $v2 = $v2.wrapping_add($v1); $v1 = rotl!($v1, 17); $v1 ^= $v2;
  83         $v2 = rotl!($v2, 32);
  84     })
  85 }
  86
  87 impl SipHasher {
  88     /// Creates a new `SipHasher` with the two initial keys set to 0.
  89     #[inline]
  90     #[stable(feature = "rust1", since = "1.0.0")]
  91     pub fn new() -> SipHasher {
  92         SipHasher::new_with_keys(0, 0)
  93     }
  94
  95     /// Creates a `SipHasher` that is keyed off the provided keys.
  96     #[inline]
  97     #[stable(feature = "rust1", since = "1.0.0")]
  98     pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher {
  99         let mut state = SipHasher {
 100             k0: key0,
 101             k1: key1,
 102             length: 0,
 103             v0: 0,
 104             v1: 0,
 105             v2: 0,
 106             v3: 0,
 107             tail: 0,
 108             ntail: 0,
 109         };
 110         state.reset();
 111         state
 112     }
 113
 114     #[inline]
 115     fn reset(&mut self) {
 116         self.length = 0;
 117         self.v0 = self.k0 ^ 0x736f6d6570736575;
 118         self.v1 = self.k1 ^ 0x646f72616e646f6d;
 119         self.v2 = self.k0 ^ 0x6c7967656e657261;
 120         self.v3 = self.k1 ^ 0x7465646279746573;
 121         self.ntail = 0;
 122     }
 123
 124     #[inline]
 125     fn write(&mut self, msg: &[u8]) {
 126         let length = msg.len();
 127         self.length += length;
 128
 129         let mut needed = 0;
 130
 131         if self.ntail != 0 {
 132             needed = 8 - self.ntail;
 133             if length < needed {
 134                 self.tail |= u8to64_le!(msg, 0, length) << 8*self.ntail;
 135                 self.ntail += length;
 136                 return
 137             }
 138
 139             let m = self.tail | u8to64_le!(msg, 0, needed) << 8*self.ntail;
 140
 141             self.v3 ^= m;
 142             compress!(self.v0, self.v1, self.v2, self.v3);
 143             compress!(self.v0, self.v1, self.v2, self.v3);
 144             self.v0 ^= m;
 145
 146             self.ntail = 0;
 147         }
 148
 149         // Buffered tail is now flushed, process new input.
 150         let len = length - needed;
 151         let end = len & (!0x7);
 152         let left = len & 0x7;
 153
 154         let mut i = needed;
 155         while i < end {
 156             let mi = u8to64_le!(msg, i);
 157
 158             self.v3 ^= mi;
 159             compress!(self.v0, self.v1, self.v2, self.v3);
 160             compress!(self.v0, self.v1, self.v2, self.v3);
 161             self.v0 ^= mi;
 162
 163             i += 8;
 164         }
 165
 166         self.tail = u8to64_le!(msg, i, left);
 167         self.ntail = left;
 168     }
 169 }
 170
 171 #[stable(feature = "rust1", since = "1.0.0")]
 172 impl Hasher for SipHasher {
 173     #[inline]
 174     fn write(&mut self, msg: &[u8]) {
 175         self.write(msg)
 176     }
 177
 178     #[inline]
 179     fn finish(&self) -> u64 {
 180         let mut v0 = self.v0;
 181         let mut v1 = self.v1;
 182         let mut v2 = self.v2;
 183         let mut v3 = self.v3;
 184
 185         let b: u64 = ((self.length as u64 & 0xff) << 56) | self.tail;
 186
 187         v3 ^= b;
 188         compress!(v0, v1, v2, v3);
 189         compress!(v0, v1, v2, v3);
 190         v0 ^= b;
 191
 192         v2 ^= 0xff;
 193         compress!(v0, v1, v2, v3);
 194         compress!(v0, v1, v2, v3);
 195         compress!(v0, v1, v2, v3);
 196         compress!(v0, v1, v2, v3);
 197
 198         v0 ^ v1 ^ v2 ^ v3
 199     }
 200 }
 201
 202 #[stable(feature = "rust1", since = "1.0.0")]
 203 impl Clone for SipHasher {
 204     #[inline]
 205     fn clone(&self) -> SipHasher {
 206         SipHasher {
 207             k0: self.k0,
 208             k1: self.k1,
 209             length: self.length,
 210             v0: self.v0,
 211             v1: self.v1,
 212             v2: self.v2,
 213             v3: self.v3,
 214             tail: self.tail,
 215             ntail: self.ntail,
 216         }
 217     }
 218 }
 219
 220 #[stable(feature = "rust1", since = "1.0.0")]
 221 impl Default for SipHasher {
 222     fn default() -> SipHasher {
 223         SipHasher::new()
 224     }
 225 }