tanjent@gmail.com | f3b7897 | 2012-03-01 03:38:55 +0000 | [diff] [blame] | 1 | //----------------------------------------------------------------------------- |
| 2 | // MurmurHash2 was written by Austin Appleby, and is placed in the public |
| 3 | // domain. The author hereby disclaims copyright to this source code. |
| 4 | |
| 5 | // Note - This code makes a few assumptions about how your machine behaves - |
| 6 | |
| 7 | // 1. We can read a 4-byte value from any address without crashing |
| 8 | // 2. sizeof(int) == 4 |
| 9 | |
| 10 | // And it has a few limitations - |
| 11 | |
| 12 | // 1. It will not work incrementally. |
| 13 | // 2. It will not produce the same results on little-endian and big-endian |
| 14 | // machines. |
| 15 | |
| 16 | #include "MurmurHash2.h" |
| 17 | |
| 18 | //----------------------------------------------------------------------------- |
| 19 | // Platform-specific functions and macros |
| 20 | |
| 21 | // Microsoft Visual Studio |
| 22 | |
| 23 | #if defined(_MSC_VER) |
| 24 | |
| 25 | #define BIG_CONSTANT(x) (x) |
| 26 | |
| 27 | // Other compilers |
| 28 | |
| 29 | #else // defined(_MSC_VER) |
| 30 | |
| 31 | #define BIG_CONSTANT(x) (x##LLU) |
| 32 | |
| 33 | #endif // !defined(_MSC_VER) |
| 34 | |
| 35 | //----------------------------------------------------------------------------- |
| 36 | |
| 37 | uint32_t MurmurHash2 ( const void * key, int len, uint32_t seed ) |
| 38 | { |
| 39 | // 'm' and 'r' are mixing constants generated offline. |
| 40 | // They're not really 'magic', they just happen to work well. |
| 41 | |
| 42 | const uint32_t m = 0x5bd1e995; |
| 43 | const int r = 24; |
| 44 | |
| 45 | // Initialize the hash to a 'random' value |
| 46 | |
| 47 | uint32_t h = seed ^ len; |
| 48 | |
| 49 | // Mix 4 bytes at a time into the hash |
| 50 | |
| 51 | const unsigned char * data = (const unsigned char *)key; |
| 52 | |
| 53 | while(len >= 4) |
| 54 | { |
| 55 | uint32_t k = *(uint32_t*)data; |
| 56 | |
| 57 | k *= m; |
| 58 | k ^= k >> r; |
| 59 | k *= m; |
| 60 | |
| 61 | h *= m; |
| 62 | h ^= k; |
| 63 | |
| 64 | data += 4; |
| 65 | len -= 4; |
| 66 | } |
| 67 | |
| 68 | // Handle the last few bytes of the input array |
| 69 | |
| 70 | switch(len) |
| 71 | { |
| 72 | case 3: h ^= data[2] << 16; |
| 73 | case 2: h ^= data[1] << 8; |
| 74 | case 1: h ^= data[0]; |
| 75 | h *= m; |
| 76 | }; |
| 77 | |
| 78 | // Do a few final mixes of the hash to ensure the last few |
| 79 | // bytes are well-incorporated. |
| 80 | |
| 81 | h ^= h >> 13; |
| 82 | h *= m; |
| 83 | h ^= h >> 15; |
| 84 | |
| 85 | return h; |
| 86 | } |
| 87 | |
| 88 | //----------------------------------------------------------------------------- |
| 89 | // MurmurHash2, 64-bit versions, by Austin Appleby |
| 90 | |
| 91 | // The same caveats as 32-bit MurmurHash2 apply here - beware of alignment |
| 92 | // and endian-ness issues if used across multiple platforms. |
| 93 | |
| 94 | // 64-bit hash for 64-bit platforms |
| 95 | |
| 96 | uint64_t MurmurHash64A ( const void * key, int len, uint64_t seed ) |
| 97 | { |
| 98 | const uint64_t m = BIG_CONSTANT(0xc6a4a7935bd1e995); |
| 99 | const int r = 47; |
| 100 | |
| 101 | uint64_t h = seed ^ (len * m); |
| 102 | |
| 103 | const uint64_t * data = (const uint64_t *)key; |
| 104 | const uint64_t * end = data + (len/8); |
| 105 | |
| 106 | while(data != end) |
| 107 | { |
| 108 | uint64_t k = *data++; |
| 109 | |
| 110 | k *= m; |
| 111 | k ^= k >> r; |
| 112 | k *= m; |
| 113 | |
| 114 | h ^= k; |
| 115 | h *= m; |
| 116 | } |
| 117 | |
| 118 | const unsigned char * data2 = (const unsigned char*)data; |
| 119 | |
| 120 | switch(len & 7) |
| 121 | { |
| 122 | case 7: h ^= uint64_t(data2[6]) << 48; |
| 123 | case 6: h ^= uint64_t(data2[5]) << 40; |
| 124 | case 5: h ^= uint64_t(data2[4]) << 32; |
| 125 | case 4: h ^= uint64_t(data2[3]) << 24; |
| 126 | case 3: h ^= uint64_t(data2[2]) << 16; |
| 127 | case 2: h ^= uint64_t(data2[1]) << 8; |
| 128 | case 1: h ^= uint64_t(data2[0]); |
| 129 | h *= m; |
| 130 | }; |
| 131 | |
| 132 | h ^= h >> r; |
| 133 | h *= m; |
| 134 | h ^= h >> r; |
| 135 | |
| 136 | return h; |
| 137 | } |
| 138 | |
| 139 | |
| 140 | // 64-bit hash for 32-bit platforms |
| 141 | |
| 142 | uint64_t MurmurHash64B ( const void * key, int len, uint64_t seed ) |
| 143 | { |
| 144 | const uint32_t m = 0x5bd1e995; |
| 145 | const int r = 24; |
| 146 | |
| 147 | uint32_t h1 = uint32_t(seed) ^ len; |
| 148 | uint32_t h2 = uint32_t(seed >> 32); |
| 149 | |
| 150 | const uint32_t * data = (const uint32_t *)key; |
| 151 | |
| 152 | while(len >= 8) |
| 153 | { |
| 154 | uint32_t k1 = *data++; |
| 155 | k1 *= m; k1 ^= k1 >> r; k1 *= m; |
| 156 | h1 *= m; h1 ^= k1; |
| 157 | len -= 4; |
| 158 | |
| 159 | uint32_t k2 = *data++; |
| 160 | k2 *= m; k2 ^= k2 >> r; k2 *= m; |
| 161 | h2 *= m; h2 ^= k2; |
| 162 | len -= 4; |
| 163 | } |
| 164 | |
| 165 | if(len >= 4) |
| 166 | { |
| 167 | uint32_t k1 = *data++; |
| 168 | k1 *= m; k1 ^= k1 >> r; k1 *= m; |
| 169 | h1 *= m; h1 ^= k1; |
| 170 | len -= 4; |
| 171 | } |
| 172 | |
| 173 | switch(len) |
| 174 | { |
| 175 | case 3: h2 ^= ((unsigned char*)data)[2] << 16; |
| 176 | case 2: h2 ^= ((unsigned char*)data)[1] << 8; |
| 177 | case 1: h2 ^= ((unsigned char*)data)[0]; |
| 178 | h2 *= m; |
| 179 | }; |
| 180 | |
| 181 | h1 ^= h2 >> 18; h1 *= m; |
| 182 | h2 ^= h1 >> 22; h2 *= m; |
| 183 | h1 ^= h2 >> 17; h1 *= m; |
| 184 | h2 ^= h1 >> 19; h2 *= m; |
| 185 | |
| 186 | uint64_t h = h1; |
| 187 | |
| 188 | h = (h << 32) | h2; |
| 189 | |
| 190 | return h; |
| 191 | } |
| 192 | |
| 193 | //----------------------------------------------------------------------------- |
| 194 | // MurmurHash2A, by Austin Appleby |
| 195 | |
| 196 | // This is a variant of MurmurHash2 modified to use the Merkle-Damgard |
| 197 | // construction. Bulk speed should be identical to Murmur2, small-key speed |
| 198 | // will be 10%-20% slower due to the added overhead at the end of the hash. |
| 199 | |
| 200 | // This variant fixes a minor issue where null keys were more likely to |
| 201 | // collide with each other than expected, and also makes the function |
| 202 | // more amenable to incremental implementations. |
| 203 | |
| 204 | #define mmix(h,k) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; } |
| 205 | |
| 206 | uint32_t MurmurHash2A ( const void * key, int len, uint32_t seed ) |
| 207 | { |
| 208 | const uint32_t m = 0x5bd1e995; |
| 209 | const int r = 24; |
| 210 | uint32_t l = len; |
| 211 | |
| 212 | const unsigned char * data = (const unsigned char *)key; |
| 213 | |
| 214 | uint32_t h = seed; |
| 215 | |
| 216 | while(len >= 4) |
| 217 | { |
| 218 | uint32_t k = *(uint32_t*)data; |
| 219 | |
| 220 | mmix(h,k); |
| 221 | |
| 222 | data += 4; |
| 223 | len -= 4; |
| 224 | } |
| 225 | |
| 226 | uint32_t t = 0; |
| 227 | |
| 228 | switch(len) |
| 229 | { |
| 230 | case 3: t ^= data[2] << 16; |
| 231 | case 2: t ^= data[1] << 8; |
| 232 | case 1: t ^= data[0]; |
| 233 | }; |
| 234 | |
| 235 | mmix(h,t); |
| 236 | mmix(h,l); |
| 237 | |
| 238 | h ^= h >> 13; |
| 239 | h *= m; |
| 240 | h ^= h >> 15; |
| 241 | |
| 242 | return h; |
| 243 | } |
| 244 | |
| 245 | //----------------------------------------------------------------------------- |
| 246 | // CMurmurHash2A, by Austin Appleby |
| 247 | |
| 248 | // This is a sample implementation of MurmurHash2A designed to work |
| 249 | // incrementally. |
| 250 | |
| 251 | // Usage - |
| 252 | |
| 253 | // CMurmurHash2A hasher |
| 254 | // hasher.Begin(seed); |
| 255 | // hasher.Add(data1,size1); |
| 256 | // hasher.Add(data2,size2); |
| 257 | // ... |
| 258 | // hasher.Add(dataN,sizeN); |
| 259 | // uint32_t hash = hasher.End() |
| 260 | |
| 261 | class CMurmurHash2A |
| 262 | { |
| 263 | public: |
| 264 | |
| 265 | void Begin ( uint32_t seed = 0 ) |
| 266 | { |
| 267 | m_hash = seed; |
| 268 | m_tail = 0; |
| 269 | m_count = 0; |
| 270 | m_size = 0; |
| 271 | } |
| 272 | |
| 273 | void Add ( const unsigned char * data, int len ) |
| 274 | { |
| 275 | m_size += len; |
| 276 | |
| 277 | MixTail(data,len); |
| 278 | |
| 279 | while(len >= 4) |
| 280 | { |
| 281 | uint32_t k = *(uint32_t*)data; |
| 282 | |
| 283 | mmix(m_hash,k); |
| 284 | |
| 285 | data += 4; |
| 286 | len -= 4; |
| 287 | } |
| 288 | |
| 289 | MixTail(data,len); |
| 290 | } |
| 291 | |
| 292 | uint32_t End ( void ) |
| 293 | { |
| 294 | mmix(m_hash,m_tail); |
| 295 | mmix(m_hash,m_size); |
| 296 | |
| 297 | m_hash ^= m_hash >> 13; |
| 298 | m_hash *= m; |
| 299 | m_hash ^= m_hash >> 15; |
| 300 | |
| 301 | return m_hash; |
| 302 | } |
| 303 | |
| 304 | private: |
| 305 | |
| 306 | static const uint32_t m = 0x5bd1e995; |
| 307 | static const int r = 24; |
| 308 | |
| 309 | void MixTail ( const unsigned char * & data, int & len ) |
| 310 | { |
| 311 | while( len && ((len<4) || m_count) ) |
| 312 | { |
| 313 | m_tail |= (*data++) << (m_count * 8); |
| 314 | |
| 315 | m_count++; |
| 316 | len--; |
| 317 | |
| 318 | if(m_count == 4) |
| 319 | { |
| 320 | mmix(m_hash,m_tail); |
| 321 | m_tail = 0; |
| 322 | m_count = 0; |
| 323 | } |
| 324 | } |
| 325 | } |
| 326 | |
| 327 | uint32_t m_hash; |
| 328 | uint32_t m_tail; |
| 329 | uint32_t m_count; |
| 330 | uint32_t m_size; |
| 331 | }; |
| 332 | |
| 333 | //----------------------------------------------------------------------------- |
| 334 | // MurmurHashNeutral2, by Austin Appleby |
| 335 | |
| 336 | // Same as MurmurHash2, but endian- and alignment-neutral. |
| 337 | // Half the speed though, alas. |
| 338 | |
| 339 | uint32_t MurmurHashNeutral2 ( const void * key, int len, uint32_t seed ) |
| 340 | { |
| 341 | const uint32_t m = 0x5bd1e995; |
| 342 | const int r = 24; |
| 343 | |
| 344 | uint32_t h = seed ^ len; |
| 345 | |
| 346 | const unsigned char * data = (const unsigned char *)key; |
| 347 | |
| 348 | while(len >= 4) |
| 349 | { |
| 350 | uint32_t k; |
| 351 | |
| 352 | k = data[0]; |
| 353 | k |= data[1] << 8; |
| 354 | k |= data[2] << 16; |
| 355 | k |= data[3] << 24; |
| 356 | |
| 357 | k *= m; |
| 358 | k ^= k >> r; |
| 359 | k *= m; |
| 360 | |
| 361 | h *= m; |
| 362 | h ^= k; |
| 363 | |
| 364 | data += 4; |
| 365 | len -= 4; |
| 366 | } |
| 367 | |
| 368 | switch(len) |
| 369 | { |
| 370 | case 3: h ^= data[2] << 16; |
| 371 | case 2: h ^= data[1] << 8; |
| 372 | case 1: h ^= data[0]; |
| 373 | h *= m; |
| 374 | }; |
| 375 | |
| 376 | h ^= h >> 13; |
| 377 | h *= m; |
| 378 | h ^= h >> 15; |
| 379 | |
| 380 | return h; |
| 381 | } |
| 382 | |
| 383 | //----------------------------------------------------------------------------- |
| 384 | // MurmurHashAligned2, by Austin Appleby |
| 385 | |
| 386 | // Same algorithm as MurmurHash2, but only does aligned reads - should be safer |
| 387 | // on certain platforms. |
| 388 | |
| 389 | // Performance will be lower than MurmurHash2 |
| 390 | |
| 391 | #define MIX(h,k,m) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; } |
| 392 | |
| 393 | |
| 394 | uint32_t MurmurHashAligned2 ( const void * key, int len, uint32_t seed ) |
| 395 | { |
| 396 | const uint32_t m = 0x5bd1e995; |
| 397 | const int r = 24; |
| 398 | |
| 399 | const unsigned char * data = (const unsigned char *)key; |
| 400 | |
| 401 | uint32_t h = seed ^ len; |
| 402 | |
| 403 | int align = (uint64_t)data & 3; |
| 404 | |
| 405 | if(align && (len >= 4)) |
| 406 | { |
| 407 | // Pre-load the temp registers |
| 408 | |
| 409 | uint32_t t = 0, d = 0; |
| 410 | |
| 411 | switch(align) |
| 412 | { |
| 413 | case 1: t |= data[2] << 16; |
| 414 | case 2: t |= data[1] << 8; |
| 415 | case 3: t |= data[0]; |
| 416 | } |
| 417 | |
| 418 | t <<= (8 * align); |
| 419 | |
| 420 | data += 4-align; |
| 421 | len -= 4-align; |
| 422 | |
| 423 | int sl = 8 * (4-align); |
| 424 | int sr = 8 * align; |
| 425 | |
| 426 | // Mix |
| 427 | |
| 428 | while(len >= 4) |
| 429 | { |
| 430 | d = *(uint32_t *)data; |
| 431 | t = (t >> sr) | (d << sl); |
| 432 | |
| 433 | uint32_t k = t; |
| 434 | |
| 435 | MIX(h,k,m); |
| 436 | |
| 437 | t = d; |
| 438 | |
| 439 | data += 4; |
| 440 | len -= 4; |
| 441 | } |
| 442 | |
| 443 | // Handle leftover data in temp registers |
| 444 | |
| 445 | d = 0; |
| 446 | |
| 447 | if(len >= align) |
| 448 | { |
| 449 | switch(align) |
| 450 | { |
| 451 | case 3: d |= data[2] << 16; |
| 452 | case 2: d |= data[1] << 8; |
| 453 | case 1: d |= data[0]; |
| 454 | } |
| 455 | |
| 456 | uint32_t k = (t >> sr) | (d << sl); |
| 457 | MIX(h,k,m); |
| 458 | |
| 459 | data += align; |
| 460 | len -= align; |
| 461 | |
| 462 | //---------- |
| 463 | // Handle tail bytes |
| 464 | |
| 465 | switch(len) |
| 466 | { |
| 467 | case 3: h ^= data[2] << 16; |
| 468 | case 2: h ^= data[1] << 8; |
| 469 | case 1: h ^= data[0]; |
| 470 | h *= m; |
| 471 | }; |
| 472 | } |
| 473 | else |
| 474 | { |
| 475 | switch(len) |
| 476 | { |
| 477 | case 3: d |= data[2] << 16; |
| 478 | case 2: d |= data[1] << 8; |
| 479 | case 1: d |= data[0]; |
| 480 | case 0: h ^= (t >> sr) | (d << sl); |
| 481 | h *= m; |
| 482 | } |
| 483 | } |
| 484 | |
| 485 | h ^= h >> 13; |
| 486 | h *= m; |
| 487 | h ^= h >> 15; |
| 488 | |
| 489 | return h; |
| 490 | } |
| 491 | else |
| 492 | { |
| 493 | while(len >= 4) |
| 494 | { |
| 495 | uint32_t k = *(uint32_t *)data; |
| 496 | |
| 497 | MIX(h,k,m); |
| 498 | |
| 499 | data += 4; |
| 500 | len -= 4; |
| 501 | } |
| 502 | |
| 503 | //---------- |
| 504 | // Handle tail bytes |
| 505 | |
| 506 | switch(len) |
| 507 | { |
| 508 | case 3: h ^= data[2] << 16; |
| 509 | case 2: h ^= data[1] << 8; |
| 510 | case 1: h ^= data[0]; |
| 511 | h *= m; |
| 512 | }; |
| 513 | |
| 514 | h ^= h >> 13; |
| 515 | h *= m; |
| 516 | h ^= h >> 15; |
| 517 | |
| 518 | return h; |
| 519 | } |
| 520 | } |
| 521 | |
| 522 | //----------------------------------------------------------------------------- |
| 523 | |