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| 1 // Copyright (c) 2014 Google, Inc. |
| 2 // |
| 3 // Permission is hereby granted, free of charge, to any person obtaining a copy |
| 4 // of this software and associated documentation files (the "Software"), to deal |
| 5 // in the Software without restriction, including without limitation the rights |
| 6 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| 7 // copies of the Software, and to permit persons to whom the Software is |
| 8 // furnished to do so, subject to the following conditions: |
| 9 // |
| 10 // The above copyright notice and this permission notice shall be included in |
| 11 // all copies or substantial portions of the Software. |
| 12 // |
| 13 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 14 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 15 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| 16 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 17 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| 18 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| 19 // THE SOFTWARE. |
| 20 // |
| 21 // FarmHash, by Geoff Pike |
| 22 |
| 23 // |
| 24 // http://code.google.com/p/farmhash/ |
| 25 // |
| 26 // This file provides a few functions for hashing strings and other |
| 27 // data. All of them are high-quality functions in the sense that |
| 28 // they do well on standard tests such as Austin Appleby's SMHasher. |
| 29 // They're also fast. FarmHash is the successor to CityHash. |
| 30 // |
| 31 // Functions in the FarmHash family are not suitable for cryptography. |
| 32 // |
| 33 // WARNING: This code has been only lightly tested on big-endian platforms! |
| 34 // It is known to work well on little-endian platforms that have a small penalty |
| 35 // for unaligned reads, such as current Intel and AMD moderate-to-high-end CPUs. |
| 36 // It should work on all 32-bit and 64-bit platforms that allow unaligned reads; |
| 37 // bug reports are welcome. |
| 38 // |
| 39 // By the way, for some hash functions, given strings a and b, the hash |
| 40 // of a+b is easily derived from the hashes of a and b. This property |
| 41 // doesn't hold for any hash functions in this file. |
| 42 |
| 43 #ifndef FARM_HASH_H_ |
| 44 #define FARM_HASH_H_ |
| 45 |
| 46 #include <assert.h> |
| 47 #include <stdint.h> |
| 48 #include <stdlib.h> |
| 49 #include <string.h> // for memcpy and memset |
| 50 #include <utility> |
| 51 |
| 52 #ifndef NAMESPACE_FOR_HASH_FUNCTIONS |
| 53 #define NAMESPACE_FOR_HASH_FUNCTIONS util |
| 54 #endif |
| 55 |
| 56 namespace NAMESPACE_FOR_HASH_FUNCTIONS { |
| 57 |
| 58 #if defined(FARMHASH_UINT128_T_DEFINED) |
| 59 inline uint64_t Uint128Low64(const uint128_t x) { |
| 60 return static_cast<uint64_t>(x); |
| 61 } |
| 62 inline uint64_t Uint128High64(const uint128_t x) { |
| 63 return static_cast<uint64_t>(x >> 64); |
| 64 } |
| 65 inline uint128_t Uint128(uint64_t lo, uint64_t hi) { |
| 66 return lo + (((uint128_t)hi) << 64); |
| 67 } |
| 68 #else |
| 69 typedef std::pair<uint64_t, uint64_t> uint128_t; |
| 70 inline uint64_t Uint128Low64(const uint128_t x) { return x.first; } |
| 71 inline uint64_t Uint128High64(const uint128_t x) { return x.second; } |
| 72 inline uint128_t Uint128(uint64_t lo, uint64_t hi) { return uint128_t(lo, hi); } |
| 73 #endif |
| 74 |
| 75 |
| 76 // BASIC STRING HASHING |
| 77 |
| 78 // Hash function for a byte array. |
| 79 // May change from time to time, may differ on different platforms, may differ |
| 80 // depending on NDEBUG. |
| 81 size_t Hash(const char* s, size_t len); |
| 82 |
| 83 // Hash function for a byte array. Most useful in 32-bit binaries. |
| 84 // May change from time to time, may differ on different platforms, may differ |
| 85 // depending on NDEBUG. |
| 86 uint32_t Hash32(const char* s, size_t len); |
| 87 |
| 88 // Hash function for a byte array. For convenience, a 32-bit seed is also |
| 89 // hashed into the result. |
| 90 // May change from time to time, may differ on different platforms, may differ |
| 91 // depending on NDEBUG. |
| 92 uint32_t Hash32WithSeed(const char* s, size_t len, uint32_t seed); |
| 93 |
| 94 // Hash 128 input bits down to 64 bits of output. |
| 95 // Hash function for a byte array. |
| 96 // May change from time to time, may differ on different platforms, may differ |
| 97 // depending on NDEBUG. |
| 98 uint64_t Hash64(const char* s, size_t len); |
| 99 |
| 100 // Hash function for a byte array. For convenience, a 64-bit seed is also |
| 101 // hashed into the result. |
| 102 // May change from time to time, may differ on different platforms, may differ |
| 103 // depending on NDEBUG. |
| 104 uint64_t Hash64WithSeed(const char* s, size_t len, uint64_t seed); |
| 105 |
| 106 // Hash function for a byte array. For convenience, two seeds are also |
| 107 // hashed into the result. |
| 108 // May change from time to time, may differ on different platforms, may differ |
| 109 // depending on NDEBUG. |
| 110 uint64_t Hash64WithSeeds(const char* s, size_t len, |
| 111 uint64_t seed0, uint64_t seed1); |
| 112 |
| 113 // Hash function for a byte array. |
| 114 // May change from time to time, may differ on different platforms, may differ |
| 115 // depending on NDEBUG. |
| 116 uint128_t Hash128(const char* s, size_t len); |
| 117 |
| 118 // Hash function for a byte array. For convenience, a 128-bit seed is also |
| 119 // hashed into the result. |
| 120 // May change from time to time, may differ on different platforms, may differ |
| 121 // depending on NDEBUG. |
| 122 uint128_t Hash128WithSeed(const char* s, size_t len, uint128_t seed); |
| 123 |
| 124 // BASIC NON-STRING HASHING |
| 125 |
| 126 // This is intended to be a reasonably good hash function. |
| 127 // May change from time to time, may differ on different platforms, may differ |
| 128 // depending on NDEBUG. |
| 129 inline uint64_t Hash128to64(uint128_t x) { |
| 130 // Murmur-inspired hashing. |
| 131 const uint64_t kMul = 0x9ddfea08eb382d69ULL; |
| 132 uint64_t a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul; |
| 133 a ^= (a >> 47); |
| 134 uint64_t b = (Uint128High64(x) ^ a) * kMul; |
| 135 b ^= (b >> 47); |
| 136 b *= kMul; |
| 137 return b; |
| 138 } |
| 139 |
| 140 // FINGERPRINTING (i.e., good, portable, forever-fixed hash functions) |
| 141 |
| 142 // Fingerprint function for a byte array. Most useful in 32-bit binaries. |
| 143 uint32_t Fingerprint32(const char* s, size_t len); |
| 144 |
| 145 // Fingerprint function for a byte array. |
| 146 uint64_t Fingerprint64(const char* s, size_t len); |
| 147 |
| 148 // Fingerprint function for a byte array. |
| 149 uint128_t Fingerprint128(const char* s, size_t len); |
| 150 |
| 151 // This is intended to be a good fingerprinting primitive. |
| 152 // See below for more overloads. |
| 153 inline uint64_t Fingerprint(uint128_t x) { |
| 154 // Murmur-inspired hashing. |
| 155 const uint64_t kMul = 0x9ddfea08eb382d69ULL; |
| 156 uint64_t a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul; |
| 157 a ^= (a >> 47); |
| 158 uint64_t b = (Uint128High64(x) ^ a) * kMul; |
| 159 b ^= (b >> 44); |
| 160 b *= kMul; |
| 161 b ^= (b >> 41); |
| 162 b *= kMul; |
| 163 return b; |
| 164 } |
| 165 |
| 166 // This is intended to be a good fingerprinting primitive. |
| 167 inline uint64_t Fingerprint(uint64_t x) { |
| 168 // Murmur-inspired hashing. |
| 169 const uint64_t kMul = 0x9ddfea08eb382d69ULL; |
| 170 uint64_t b = x * kMul; |
| 171 b ^= (b >> 44); |
| 172 b *= kMul; |
| 173 b ^= (b >> 41); |
| 174 b *= kMul; |
| 175 return b; |
| 176 } |
| 177 |
| 178 #ifndef FARMHASH_NO_CXX_STRING |
| 179 |
| 180 // Convenience functions to hash or fingerprint C++ strings. |
| 181 // These require that Str::data() return a pointer to the first char |
| 182 // (as a const char*) and that Str::length() return the string's length; |
| 183 // they work with std::string, for example. |
| 184 |
| 185 // Hash function for a byte array. |
| 186 // May change from time to time, may differ on different platforms, may differ |
| 187 // depending on NDEBUG. |
| 188 template <typename Str> |
| 189 inline size_t Hash(const Str& s) { |
| 190 assert(sizeof(s[0]) == 1); |
| 191 return Hash(s.data(), s.length()); |
| 192 } |
| 193 |
| 194 // Hash function for a byte array. Most useful in 32-bit binaries. |
| 195 // May change from time to time, may differ on different platforms, may differ |
| 196 // depending on NDEBUG. |
| 197 template <typename Str> |
| 198 inline uint32_t Hash32(const Str& s) { |
| 199 assert(sizeof(s[0]) == 1); |
| 200 return Hash32(s.data(), s.length()); |
| 201 } |
| 202 |
| 203 // Hash function for a byte array. For convenience, a 32-bit seed is also |
| 204 // hashed into the result. |
| 205 // May change from time to time, may differ on different platforms, may differ |
| 206 // depending on NDEBUG. |
| 207 template <typename Str> |
| 208 inline uint32_t Hash32WithSeed(const Str& s, uint32_t seed) { |
| 209 assert(sizeof(s[0]) == 1); |
| 210 return Hash32WithSeed(s.data(), s.length(), seed); |
| 211 } |
| 212 |
| 213 // Hash 128 input bits down to 64 bits of output. |
| 214 // Hash function for a byte array. |
| 215 // May change from time to time, may differ on different platforms, may differ |
| 216 // depending on NDEBUG. |
| 217 template <typename Str> |
| 218 inline uint64_t Hash64(const Str& s) { |
| 219 assert(sizeof(s[0]) == 1); |
| 220 return Hash64(s.data(), s.length()); |
| 221 } |
| 222 |
| 223 // Hash function for a byte array. For convenience, a 64-bit seed is also |
| 224 // hashed into the result. |
| 225 // May change from time to time, may differ on different platforms, may differ |
| 226 // depending on NDEBUG. |
| 227 template <typename Str> |
| 228 inline uint64_t Hash64WithSeed(const Str& s, uint64_t seed) { |
| 229 assert(sizeof(s[0]) == 1); |
| 230 return Hash64WithSeed(s.data(), s.length(), seed); |
| 231 } |
| 232 |
| 233 // Hash function for a byte array. For convenience, two seeds are also |
| 234 // hashed into the result. |
| 235 // May change from time to time, may differ on different platforms, may differ |
| 236 // depending on NDEBUG. |
| 237 template <typename Str> |
| 238 inline uint64_t Hash64WithSeeds(const Str& s, uint64_t seed0, uint64_t seed1) { |
| 239 assert(sizeof(s[0]) == 1); |
| 240 return Hash64WithSeeds(s.data(), s.length(), seed0, seed1); |
| 241 } |
| 242 |
| 243 // Hash function for a byte array. |
| 244 // May change from time to time, may differ on different platforms, may differ |
| 245 // depending on NDEBUG. |
| 246 template <typename Str> |
| 247 inline uint128_t Hash128(const Str& s) { |
| 248 assert(sizeof(s[0]) == 1); |
| 249 return Hash128(s.data(), s.length()); |
| 250 } |
| 251 |
| 252 // Hash function for a byte array. For convenience, a 128-bit seed is also |
| 253 // hashed into the result. |
| 254 // May change from time to time, may differ on different platforms, may differ |
| 255 // depending on NDEBUG. |
| 256 template <typename Str> |
| 257 inline uint128_t Hash128WithSeed(const Str& s, uint128_t seed) { |
| 258 assert(sizeof(s[0]) == 1); |
| 259 return Hash128(s.data(), s.length(), seed); |
| 260 } |
| 261 |
| 262 // FINGERPRINTING (i.e., good, portable, forever-fixed hash functions) |
| 263 |
| 264 // Fingerprint function for a byte array. Most useful in 32-bit binaries. |
| 265 template <typename Str> |
| 266 inline uint32_t Fingerprint32(const Str& s) { |
| 267 assert(sizeof(s[0]) == 1); |
| 268 return Fingerprint32(s.data(), s.length()); |
| 269 } |
| 270 |
| 271 // Fingerprint 128 input bits down to 64 bits of output. |
| 272 // Fingerprint function for a byte array. |
| 273 template <typename Str> |
| 274 inline uint64_t Fingerprint64(const Str& s) { |
| 275 assert(sizeof(s[0]) == 1); |
| 276 return Fingerprint64(s.data(), s.length()); |
| 277 } |
| 278 |
| 279 // Fingerprint function for a byte array. |
| 280 template <typename Str> |
| 281 inline uint128_t Fingerprint128(const Str& s) { |
| 282 assert(sizeof(s[0]) == 1); |
| 283 return Fingerprint128(s.data(), s.length()); |
| 284 } |
| 285 |
| 286 #endif |
| 287 |
| 288 } // namespace NAMESPACE_FOR_HASH_FUNCTIONS |
| 289 |
| 290 #endif // FARM_HASH_H_ |
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