vendor/siphasher/src/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 use core::cmp;
  14 use core::hash;
  15 use core::marker::PhantomData;
  16 use core::mem;
  17 use core::ptr;
  18
  19 /// An implementation of SipHash 1-3.
  20 ///
  21 /// See: <https://131002.net/siphash/>
  22 #[derive(Debug, Clone, Copy, Default)]
  23 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
  24 pub struct SipHasher13 {
  25     hasher: Hasher<Sip13Rounds>,
  26 }
  27
  28 /// An implementation of SipHash 2-4.
  29 ///
  30 /// See: <https://131002.net/siphash/>
  31 #[derive(Debug, Clone, Copy, Default)]
  32 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
  33 pub struct SipHasher24 {
  34     hasher: Hasher<Sip24Rounds>,
  35 }
  36
  37 /// An implementation of SipHash 2-4.
  38 ///
  39 /// See: <https://131002.net/siphash/>
  40 ///
  41 /// SipHash is a general-purpose hashing function: it runs at a good
  42 /// speed (competitive with Spooky and City) and permits strong _keyed_
  43 /// hashing. This lets you key your hashtables from a strong RNG, such as
  44 /// [`rand::os::OsRng`](https://doc.rust-lang.org/rand/rand/os/struct.OsRng.html).
  45 ///
  46 /// Although the SipHash algorithm is considered to be generally strong,
  47 /// it is not intended for cryptographic purposes. As such, all
  48 /// cryptographic uses of this implementation are _strongly discouraged_.
  49 #[derive(Debug, Clone, Copy, Default)]
  50 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
  51 pub struct SipHasher(SipHasher24);
  52
  53 #[derive(Debug, Clone, Copy)]
  54 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
  55 struct Hasher<S: Sip> {
  56     k0: u64,
  57     k1: u64,
  58     length: usize, // how many bytes we've processed
  59     state: State,  // hash State
  60     tail: u64,     // unprocessed bytes le
  61     ntail: usize,  // how many bytes in tail are valid
  62     _marker: PhantomData<S>,
  63 }
  64
  65 #[derive(Debug, Clone, Copy)]
  66 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
  67 struct State {
  68     // v0, v2 and v1, v3 show up in pairs in the algorithm,
  69     // and simd implementations of SipHash will use vectors
  70     // of v02 and v13. By placing them in this order in the struct,
  71     // the compiler can pick up on just a few simd optimizations by itself.
  72     v0: u64,
  73     v2: u64,
  74     v1: u64,
  75     v3: u64,
  76 }
  77
  78 macro_rules! compress {
  79     ($state:expr) => {{
  80         compress!($state.v0, $state.v1, $state.v2, $state.v3)
  81     }};
  82     ($v0:expr, $v1:expr, $v2:expr, $v3:expr) => {{
  83         $v0 = $v0.wrapping_add($v1);
  84         $v1 = $v1.rotate_left(13);
  85         $v1 ^= $v0;
  86         $v0 = $v0.rotate_left(32);
  87         $v2 = $v2.wrapping_add($v3);
  88         $v3 = $v3.rotate_left(16);
  89         $v3 ^= $v2;
  90         $v0 = $v0.wrapping_add($v3);
  91         $v3 = $v3.rotate_left(21);
  92         $v3 ^= $v0;
  93         $v2 = $v2.wrapping_add($v1);
  94         $v1 = $v1.rotate_left(17);
  95         $v1 ^= $v2;
  96         $v2 = $v2.rotate_left(32);
  97     }};
  98 }
  99
 100 /// Loads an integer of the desired type from a byte stream, in LE order. Uses
 101 /// `copy_nonoverlapping` to let the compiler generate the most efficient way
 102 /// to load it from a possibly unaligned address.
 103 ///
 104 /// Unsafe because: unchecked indexing at `i..i+size_of(int_ty)`
 105 macro_rules! load_int_le {
 106     ($buf:expr, $i:expr, $int_ty:ident) => {{
 107         debug_assert!($i + mem::size_of::<$int_ty>() <= $buf.len());
 108         let mut data = 0 as $int_ty;
 109         ptr::copy_nonoverlapping(
 110             $buf.get_unchecked($i),
 111             &mut data as *mut _ as *mut u8,
 112             mem::size_of::<$int_ty>(),
 113         );
 114         data.to_le()
 115     }};
 116 }
 117
 118 /// Loads a u64 using up to 7 bytes of a byte slice. It looks clumsy but the
 119 /// `copy_nonoverlapping` calls that occur (via `load_int_le!`) all have fixed
 120 /// sizes and avoid calling `memcpy`, which is good for speed.
 121 ///
 122 /// Unsafe because: unchecked indexing at start..start+len
 123 #[inline]
 124 unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
 125     debug_assert!(len < 8);
 126     let mut i = 0; // current byte index (from LSB) in the output u64
 127     let mut out = 0;
 128     if i + 3 < len {
 129         out = load_int_le!(buf, start + i, u32) as u64;
 130         i += 4;
 131     }
 132     if i + 1 < len {
 133         out |= (load_int_le!(buf, start + i, u16) as u64) << (i * 8);
 134         i += 2
 135     }
 136     if i < len {
 137         out |= (*buf.get_unchecked(start + i) as u64) << (i * 8);
 138         i += 1;
 139     }
 140     debug_assert_eq!(i, len);
 141     out
 142 }
 143
 144 impl SipHasher {
 145     /// Creates a new `SipHasher` with the two initial keys set to 0.
 146     #[inline]
 147     pub fn new() -> SipHasher {
 148         SipHasher::new_with_keys(0, 0)
 149     }
 150
 151     /// Creates a `SipHasher` that is keyed off the provided keys.
 152     #[inline]
 153     pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher {
 154         SipHasher(SipHasher24::new_with_keys(key0, key1))
 155     }
 156
 157     /// Get the keys used by this hasher
 158     pub fn keys(&self) -> (u64, u64) {
 159         (self.0.hasher.k0, self.0.hasher.k1)
 160     }
 161 }
 162
 163 impl SipHasher13 {
 164     /// Creates a new `SipHasher13` with the two initial keys set to 0.
 165     #[inline]
 166     pub fn new() -> SipHasher13 {
 167         SipHasher13::new_with_keys(0, 0)
 168     }
 169
 170     /// Creates a `SipHasher13` that is keyed off the provided keys.
 171     #[inline]
 172     pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher13 {
 173         SipHasher13 {
 174             hasher: Hasher::new_with_keys(key0, key1),
 175         }
 176     }
 177
 178     /// Get the keys used by this hasher
 179     pub fn keys(&self) -> (u64, u64) {
 180         (self.hasher.k0, self.hasher.k1)
 181     }
 182 }
 183
 184 impl SipHasher24 {
 185     /// Creates a new `SipHasher24` with the two initial keys set to 0.
 186     #[inline]
 187     pub fn new() -> SipHasher24 {
 188         SipHasher24::new_with_keys(0, 0)
 189     }
 190
 191     /// Creates a `SipHasher24` that is keyed off the provided keys.
 192     #[inline]
 193     pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher24 {
 194         SipHasher24 {
 195             hasher: Hasher::new_with_keys(key0, key1),
 196         }
 197     }
 198
 199     /// Get the keys used by this hasher
 200     pub fn keys(&self) -> (u64, u64) {
 201         (self.hasher.k0, self.hasher.k1)
 202     }
 203 }
 204
 205 impl<S: Sip> Hasher<S> {
 206     #[inline]
 207     fn new_with_keys(key0: u64, key1: u64) -> Hasher<S> {
 208         let mut state = Hasher {
 209             k0: key0,
 210             k1: key1,
 211             length: 0,
 212             state: State {
 213                 v0: 0,
 214                 v1: 0,
 215                 v2: 0,
 216                 v3: 0,
 217             },
 218             tail: 0,
 219             ntail: 0,
 220             _marker: PhantomData,
 221         };
 222         state.reset();
 223         state
 224     }
 225
 226     #[inline]
 227     fn reset(&mut self) {
 228         self.length = 0;
 229         self.state.v0 = self.k0 ^ 0x736f6d6570736575;
 230         self.state.v1 = self.k1 ^ 0x646f72616e646f6d;
 231         self.state.v2 = self.k0 ^ 0x6c7967656e657261;
 232         self.state.v3 = self.k1 ^ 0x7465646279746573;
 233         self.ntail = 0;
 234     }
 235
 236     // A specialized write function for values with size <= 8.
 237     //
 238     // The hashing of multi-byte integers depends on endianness. E.g.:
 239     // - little-endian: `write_u32(0xDDCCBBAA)` == `write([0xAA, 0xBB, 0xCC, 0xDD])`
 240     // - big-endian:    `write_u32(0xDDCCBBAA)` == `write([0xDD, 0xCC, 0xBB, 0xAA])`
 241     //
 242     // This function does the right thing for little-endian hardware. On
 243     // big-endian hardware `x` must be byte-swapped first to give the right
 244     // behaviour. After any byte-swapping, the input must be zero-extended to
 245     // 64-bits. The caller is responsible for the byte-swapping and
 246     // zero-extension.
 247     #[inline]
 248     fn short_write<T>(&mut self, _x: T, x: u64) {
 249         let size = mem::size_of::<T>();
 250         self.length += size;
 251
 252         // The original number must be zero-extended, not sign-extended.
 253         debug_assert!(if size < 8 { x >> (8 * size) == 0 } else { true });
 254
 255         // The number of bytes needed to fill `self.tail`.
 256         let needed = 8 - self.ntail;
 257
 258         self.tail |= x << (8 * self.ntail);
 259         if size < needed {
 260             self.ntail += size;
 261             return;
 262         }
 263
 264         // `self.tail` is full, process it.
 265         self.state.v3 ^= self.tail;
 266         S::c_rounds(&mut self.state);
 267         self.state.v0 ^= self.tail;
 268
 269         self.ntail = size - needed;
 270         self.tail = if needed < 8 { x >> (8 * needed) } else { 0 };
 271     }
 272 }
 273
 274 impl hash::Hasher for SipHasher {
 275     #[inline]
 276     fn write(&mut self, msg: &[u8]) {
 277         self.0.write(msg)
 278     }
 279
 280     #[inline]
 281     fn finish(&self) -> u64 {
 282         self.0.finish()
 283     }
 284 }
 285
 286 impl hash::Hasher for SipHasher13 {
 287     #[inline]
 288     fn write(&mut self, msg: &[u8]) {
 289         self.hasher.write(msg)
 290     }
 291
 292     #[inline]
 293     fn finish(&self) -> u64 {
 294         self.hasher.finish()
 295     }
 296 }
 297
 298 impl hash::Hasher for SipHasher24 {
 299     #[inline]
 300     fn write(&mut self, msg: &[u8]) {
 301         self.hasher.write(msg)
 302     }
 303
 304     #[inline]
 305     fn finish(&self) -> u64 {
 306         self.hasher.finish()
 307     }
 308 }
 309
 310 impl<S: Sip> hash::Hasher for Hasher<S> {
 311     #[inline]
 312     fn write_usize(&mut self, i: usize) {
 313         self.short_write(i, i.to_le() as u64);
 314     }
 315
 316     #[inline]
 317     fn write_u8(&mut self, i: u8) {
 318         self.short_write(i, i as u64);
 319     }
 320
 321     #[inline]
 322     fn write_u32(&mut self, i: u32) {
 323         self.short_write(i, i.to_le() as u64);
 324     }
 325
 326     #[inline]
 327     fn write_u64(&mut self, i: u64) {
 328         self.short_write(i, i.to_le() as u64);
 329     }
 330
 331     #[inline]
 332     fn write(&mut self, msg: &[u8]) {
 333         let length = msg.len();
 334         self.length += length;
 335
 336         let mut needed = 0;
 337
 338         if self.ntail != 0 {
 339             needed = 8 - self.ntail;
 340             self.tail |= unsafe { u8to64_le(msg, 0, cmp::min(length, needed)) } << (8 * self.ntail);
 341             if length < needed {
 342                 self.ntail += length;
 343                 return;
 344             } else {
 345                 self.state.v3 ^= self.tail;
 346                 S::c_rounds(&mut self.state);
 347                 self.state.v0 ^= self.tail;
 348                 self.ntail = 0;
 349             }
 350         }
 351
 352         // Buffered tail is now flushed, process new input.
 353         let len = length - needed;
 354         let left = len & 0x7;
 355
 356         let mut i = needed;
 357         while i < len - left {
 358             let mi = unsafe { load_int_le!(msg, i, u64) };
 359
 360             self.state.v3 ^= mi;
 361             S::c_rounds(&mut self.state);
 362             self.state.v0 ^= mi;
 363
 364             i += 8;
 365         }
 366
 367         self.tail = unsafe { u8to64_le(msg, i, left) };
 368         self.ntail = left;
 369     }
 370
 371     #[inline]
 372     fn finish(&self) -> u64 {
 373         let mut state = self.state;
 374
 375         let b: u64 = ((self.length as u64 & 0xff) << 56) | self.tail;
 376
 377         state.v3 ^= b;
 378         S::c_rounds(&mut state);
 379         state.v0 ^= b;
 380
 381         state.v2 ^= 0xff;
 382         S::d_rounds(&mut state);
 383
 384         state.v0 ^ state.v1 ^ state.v2 ^ state.v3
 385     }
 386 }
 387
 388 impl<S: Sip> Default for Hasher<S> {
 389     /// Creates a `Hasher<S>` with the two initial keys set to 0.
 390     #[inline]
 391     fn default() -> Hasher<S> {
 392         Hasher::new_with_keys(0, 0)
 393     }
 394 }
 395
 396 #[doc(hidden)]
 397 trait Sip {
 398     fn c_rounds(_: &mut State);
 399     fn d_rounds(_: &mut State);
 400 }
 401
 402 #[derive(Debug, Clone, Copy, Default)]
 403 struct Sip13Rounds;
 404
 405 impl Sip for Sip13Rounds {
 406     #[inline]
 407     fn c_rounds(state: &mut State) {
 408         compress!(state);
 409     }
 410
 411     #[inline]
 412     fn d_rounds(state: &mut State) {
 413         compress!(state);
 414         compress!(state);
 415         compress!(state);
 416     }
 417 }
 418
 419 #[derive(Debug, Clone, Copy, Default)]
 420 struct Sip24Rounds;
 421
 422 impl Sip for Sip24Rounds {
 423     #[inline]
 424     fn c_rounds(state: &mut State) {
 425         compress!(state);
 426         compress!(state);
 427     }
 428
 429     #[inline]
 430     fn d_rounds(state: &mut State) {
 431         compress!(state);
 432         compress!(state);
 433         compress!(state);
 434         compress!(state);
 435     }
 436 }