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.
  12
  13 #![allow(deprecated)]
  14
  15 use marker::PhantomData;
  16 use ptr;
  17 use cmp;
  18 use mem;
  19
  20 /// An implementation of SipHash 1-3.
  21 ///
  22 /// This is currently the default hashing function used by standard library
  23 /// (eg. `collections::HashMap` uses it by default).
  24 ///
  25 /// See: https://131002.net/siphash/
  26 #[unstable(feature = "sip_hash_13", issue = "34767")]
  27 #[rustc_deprecated(since = "1.13.0",
  28                    reason = "use `std::collections::hash_map::DefaultHasher` instead")]
  29 #[derive(Debug, Clone, Default)]
  30 pub struct SipHasher13 {
  31     hasher: Hasher<Sip13Rounds>,
  32 }
  33
  34 /// An implementation of SipHash 2-4.
  35 ///
  36 /// See: https://131002.net/siphash/
  37 #[unstable(feature = "sip_hash_13", issue = "34767")]
  38 #[rustc_deprecated(since = "1.13.0",
  39                    reason = "use `std::collections::hash_map::DefaultHasher` instead")]
  40 #[derive(Debug, Clone, Default)]
  41 pub struct SipHasher24 {
  42     hasher: Hasher<Sip24Rounds>,
  43 }
  44
  45 /// An implementation of SipHash 2-4.
  46 ///
  47 /// See: https://131002.net/siphash/
  48 ///
  49 /// SipHash is a general-purpose hashing function: it runs at a good
  50 /// speed (competitive with Spooky and City) and permits strong _keyed_
  51 /// hashing. This lets you key your hashtables from a strong RNG, such as
  52 /// [`rand::os::OsRng`](https://doc.rust-lang.org/rand/rand/os/struct.OsRng.html).
  53 ///
  54 /// Although the SipHash algorithm is considered to be generally strong,
  55 /// it is not intended for cryptographic purposes. As such, all
  56 /// cryptographic uses of this implementation are _strongly discouraged_.
  57 #[stable(feature = "rust1", since = "1.0.0")]
  58 #[rustc_deprecated(since = "1.13.0",
  59                    reason = "use `std::collections::hash_map::DefaultHasher` instead")]
  60 #[derive(Debug, Clone, Default)]
  61 pub struct SipHasher(SipHasher24);
  62
  63 #[derive(Debug)]
  64 struct Hasher<S: Sip> {
  65     k0: u64,
  66     k1: u64,
  67     length: usize, // how many bytes we've processed
  68     state: State, // hash State
  69     tail: u64, // unprocessed bytes le
  70     ntail: usize, // how many bytes in tail are valid
  71     _marker: PhantomData<S>,
  72 }
  73
  74 #[derive(Debug, Clone, Copy)]
  75 struct State {
  76     // v0, v2 and v1, v3 show up in pairs in the algorithm,
  77     // and simd implementations of SipHash will use vectors
  78     // of v02 and v13. By placing them in this order in the struct,
  79     // the compiler can pick up on just a few simd optimizations by itself.
  80     v0: u64,
  81     v2: u64,
  82     v1: u64,
  83     v3: u64,
  84 }
  85
  86 macro_rules! compress {
  87     ($state:expr) => ({
  88         compress!($state.v0, $state.v1, $state.v2, $state.v3)
  89     });
  90     ($v0:expr, $v1:expr, $v2:expr, $v3:expr) =>
  91     ({
  92         $v0 = $v0.wrapping_add($v1); $v1 = $v1.rotate_left(13); $v1 ^= $v0;
  93         $v0 = $v0.rotate_left(32);
  94         $v2 = $v2.wrapping_add($v3); $v3 = $v3.rotate_left(16); $v3 ^= $v2;
  95         $v0 = $v0.wrapping_add($v3); $v3 = $v3.rotate_left(21); $v3 ^= $v0;
  96         $v2 = $v2.wrapping_add($v1); $v1 = $v1.rotate_left(17); $v1 ^= $v2;
  97         $v2 = $v2.rotate_left(32);
  98     });
  99 }
 100
 101 /// Load an integer of the desired type from a byte stream, in LE order. Uses
 102 /// `copy_nonoverlapping` to let the compiler generate the most efficient way
 103 /// to load it from a possibly unaligned address.
 104 ///
 105 /// Unsafe because: unchecked indexing at i..i+size_of(int_ty)
 106 macro_rules! load_int_le {
 107     ($buf:expr, $i:expr, $int_ty:ident) =>
 108     ({
 109        debug_assert!($i + mem::size_of::<$int_ty>() <= $buf.len());
 110        let mut data = 0 as $int_ty;
 111        ptr::copy_nonoverlapping($buf.get_unchecked($i),
 112                                 &mut data as *mut _ as *mut u8,
 113                                 mem::size_of::<$int_ty>());
 114        data.to_le()
 115     });
 116 }
 117
 118 /// Load an u64 using up to 7 bytes of a byte slice.
 119 ///
 120 /// Unsafe because: unchecked indexing at start..start+len
 121 #[inline]
 122 unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
 123     debug_assert!(len < 8);
 124     let mut i = 0; // current byte index (from LSB) in the output u64
 125     let mut out = 0;
 126     if i + 3 < len {
 127         out = load_int_le!(buf, start + i, u32) as u64;
 128         i += 4;
 129     }
 130     if i + 1 < len {
 131         out |= (load_int_le!(buf, start + i, u16) as u64) << (i * 8);
 132         i += 2
 133     }
 134     if i < len {
 135         out |= (*buf.get_unchecked(start + i) as u64) << (i * 8);
 136         i += 1;
 137     }
 138     debug_assert_eq!(i, len);
 139     out
 140 }
 141
 142 impl SipHasher {
 143     /// Creates a new `SipHasher` with the two initial keys set to 0.
 144     #[inline]
 145     #[stable(feature = "rust1", since = "1.0.0")]
 146     #[rustc_deprecated(since = "1.13.0",
 147                        reason = "use `std::collections::hash_map::DefaultHasher` instead")]
 148     pub fn new() -> SipHasher {
 149         SipHasher::new_with_keys(0, 0)
 150     }
 151
 152     /// Creates a `SipHasher` that is keyed off the provided keys.
 153     #[inline]
 154     #[stable(feature = "rust1", since = "1.0.0")]
 155     #[rustc_deprecated(since = "1.13.0",
 156                        reason = "use `std::collections::hash_map::DefaultHasher` instead")]
 157     pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher {
 158         SipHasher(SipHasher24::new_with_keys(key0, key1))
 159     }
 160 }
 161
 162 impl SipHasher13 {
 163     /// Creates a new `SipHasher13` with the two initial keys set to 0.
 164     #[inline]
 165     #[unstable(feature = "sip_hash_13", issue = "34767")]
 166     #[rustc_deprecated(since = "1.13.0",
 167                        reason = "use `std::collections::hash_map::DefaultHasher` instead")]
 168     pub fn new() -> SipHasher13 {
 169         SipHasher13::new_with_keys(0, 0)
 170     }
 171
 172     /// Creates a `SipHasher13` that is keyed off the provided keys.
 173     #[inline]
 174     #[unstable(feature = "sip_hash_13", issue = "34767")]
 175     #[rustc_deprecated(since = "1.13.0",
 176                        reason = "use `std::collections::hash_map::DefaultHasher` instead")]
 177     pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher13 {
 178         SipHasher13 {
 179             hasher: Hasher::new_with_keys(key0, key1)
 180         }
 181     }
 182 }
 183
 184 impl SipHasher24 {
 185     /// Creates a new `SipHasher24` with the two initial keys set to 0.
 186     #[inline]
 187     #[unstable(feature = "sip_hash_13", issue = "34767")]
 188     #[rustc_deprecated(since = "1.13.0",
 189                        reason = "use `std::collections::hash_map::DefaultHasher` instead")]
 190     pub fn new() -> SipHasher24 {
 191         SipHasher24::new_with_keys(0, 0)
 192     }
 193
 194     /// Creates a `SipHasher24` that is keyed off the provided keys.
 195     #[inline]
 196     #[unstable(feature = "sip_hash_13", issue = "34767")]
 197     #[rustc_deprecated(since = "1.13.0",
 198                        reason = "use `std::collections::hash_map::DefaultHasher` instead")]
 199     pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher24 {
 200         SipHasher24 {
 201             hasher: Hasher::new_with_keys(key0, key1)
 202         }
 203     }
 204 }
 205
 206 impl<S: Sip> Hasher<S> {
 207     #[inline]
 208     fn new_with_keys(key0: u64, key1: u64) -> Hasher<S> {
 209         let mut state = Hasher {
 210             k0: key0,
 211             k1: key1,
 212             length: 0,
 213             state: State {
 214                 v0: 0,
 215                 v1: 0,
 216                 v2: 0,
 217                 v3: 0,
 218             },
 219             tail: 0,
 220             ntail: 0,
 221             _marker: PhantomData,
 222         };
 223         state.reset();
 224         state
 225     }
 226
 227     #[inline]
 228     fn reset(&mut self) {
 229         self.length = 0;
 230         self.state.v0 = self.k0 ^ 0x736f6d6570736575;
 231         self.state.v1 = self.k1 ^ 0x646f72616e646f6d;
 232         self.state.v2 = self.k0 ^ 0x6c7967656e657261;
 233         self.state.v3 = self.k1 ^ 0x7465646279746573;
 234         self.ntail = 0;
 235     }
 236
 237     // Specialized write function that is only valid for buffers with len <= 8.
 238     // It's used to force inlining of write_u8 and write_usize, those would normally be inlined
 239     // except for composite types (that includes slices and str hashing because of delimiter).
 240     // Without this extra push the compiler is very reluctant to inline delimiter writes,
 241     // degrading performance substantially for the most common use cases.
 242     #[inline(always)]
 243     fn short_write(&mut self, msg: &[u8]) {
 244         debug_assert!(msg.len() <= 8);
 245         let length = msg.len();
 246         self.length += length;
 247
 248         let needed = 8 - self.ntail;
 249         let fill = cmp::min(length, needed);
 250         if fill == 8 {
 251             self.tail = unsafe { load_int_le!(msg, 0, u64) };
 252         } else {
 253             self.tail |= unsafe { u8to64_le(msg, 0, fill) } << (8 * self.ntail);
 254             if length < needed {
 255                 self.ntail += length;
 256                 return;
 257             }
 258         }
 259         self.state.v3 ^= self.tail;
 260         S::c_rounds(&mut self.state);
 261         self.state.v0 ^= self.tail;
 262
 263         // Buffered tail is now flushed, process new input.
 264         self.ntail = length - needed;
 265         self.tail = unsafe { u8to64_le(msg, needed, self.ntail) };
 266     }
 267 }
 268
 269 #[stable(feature = "rust1", since = "1.0.0")]
 270 impl super::Hasher for SipHasher {
 271     #[inline]
 272     fn write(&mut self, msg: &[u8]) {
 273         self.0.write(msg)
 274     }
 275
 276     #[inline]
 277     fn finish(&self) -> u64 {
 278         self.0.finish()
 279     }
 280 }
 281
 282 #[unstable(feature = "sip_hash_13", issue = "34767")]
 283 impl super::Hasher for SipHasher13 {
 284     #[inline]
 285     fn write(&mut self, msg: &[u8]) {
 286         self.hasher.write(msg)
 287     }
 288
 289     #[inline]
 290     fn finish(&self) -> u64 {
 291         self.hasher.finish()
 292     }
 293 }
 294
 295 #[unstable(feature = "sip_hash_13", issue = "34767")]
 296 impl super::Hasher for SipHasher24 {
 297     #[inline]
 298     fn write(&mut self, msg: &[u8]) {
 299         self.hasher.write(msg)
 300     }
 301
 302     #[inline]
 303     fn finish(&self) -> u64 {
 304         self.hasher.finish()
 305     }
 306 }
 307
 308 impl<S: Sip> super::Hasher for Hasher<S> {
 309     // see short_write comment for explanation
 310     #[inline]
 311     fn write_usize(&mut self, i: usize) {
 312         let bytes = unsafe {
 313             ::slice::from_raw_parts(&i as *const usize as *const u8, mem::size_of::<usize>())
 314         };
 315         self.short_write(bytes);
 316     }
 317
 318     // see short_write comment for explanation
 319     #[inline]
 320     fn write_u8(&mut self, i: u8) {
 321         self.short_write(&[i]);
 322     }
 323
 324     #[inline]
 325     fn write(&mut self, msg: &[u8]) {
 326         let length = msg.len();
 327         self.length += length;
 328
 329         let mut needed = 0;
 330
 331         if self.ntail != 0 {
 332             needed = 8 - self.ntail;
 333             self.tail |= unsafe { u8to64_le(msg, 0, cmp::min(length, needed)) } << 8 * self.ntail;
 334             if length < needed {
 335                 self.ntail += length;
 336                 return
 337             } else {
 338                 self.state.v3 ^= self.tail;
 339                 S::c_rounds(&mut self.state);
 340                 self.state.v0 ^= self.tail;
 341                 self.ntail = 0;
 342             }
 343         }
 344
 345         // Buffered tail is now flushed, process new input.
 346         let len = length - needed;
 347         let left = len & 0x7;
 348
 349         let mut i = needed;
 350         while i < len - left {
 351             let mi = unsafe { load_int_le!(msg, i, u64) };
 352
 353             self.state.v3 ^= mi;
 354             S::c_rounds(&mut self.state);
 355             self.state.v0 ^= mi;
 356
 357             i += 8;
 358         }
 359
 360         self.tail = unsafe { u8to64_le(msg, i, left) };
 361         self.ntail = left;
 362     }
 363
 364     #[inline]
 365     fn finish(&self) -> u64 {
 366         let mut state = self.state;
 367
 368         let b: u64 = ((self.length as u64 & 0xff) << 56) | self.tail;
 369
 370         state.v3 ^= b;
 371         S::c_rounds(&mut state);
 372         state.v0 ^= b;
 373
 374         state.v2 ^= 0xff;
 375         S::d_rounds(&mut state);
 376
 377         state.v0 ^ state.v1 ^ state.v2 ^ state.v3
 378     }
 379 }
 380
 381 impl<S: Sip> Clone for Hasher<S> {
 382     #[inline]
 383     fn clone(&self) -> Hasher<S> {
 384         Hasher {
 385             k0: self.k0,
 386             k1: self.k1,
 387             length: self.length,
 388             state: self.state,
 389             tail: self.tail,
 390             ntail: self.ntail,
 391             _marker: self._marker,
 392         }
 393     }
 394 }
 395
 396 impl<S: Sip> Default for Hasher<S> {
 397     /// Creates a `Hasher<S>` with the two initial keys set to 0.
 398     #[inline]
 399     fn default() -> Hasher<S> {
 400         Hasher::new_with_keys(0, 0)
 401     }
 402 }
 403
 404 #[doc(hidden)]
 405 trait Sip {
 406     fn c_rounds(&mut State);
 407     fn d_rounds(&mut State);
 408 }
 409
 410 #[derive(Debug, Clone, Default)]
 411 struct Sip13Rounds;
 412
 413 impl Sip for Sip13Rounds {
 414     #[inline]
 415     fn c_rounds(state: &mut State) {
 416         compress!(state);
 417     }
 418
 419     #[inline]
 420     fn d_rounds(state: &mut State) {
 421         compress!(state);
 422         compress!(state);
 423         compress!(state);
 424     }
 425 }
 426
 427 #[derive(Debug, Clone, Default)]
 428 struct Sip24Rounds;
 429
 430 impl Sip for Sip24Rounds {
 431     #[inline]
 432     fn c_rounds(state: &mut State) {
 433         compress!(state);
 434         compress!(state);
 435     }
 436
 437     #[inline]
 438     fn d_rounds(state: &mut State) {
 439         compress!(state);
 440         compress!(state);
 441         compress!(state);
 442         compress!(state);
 443     }
 444 }