Meson WrapDB for Google's cityhash.
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city.h 4.8KB

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  1. // Copyright (c) 2011 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. // CityHash, by Geoff Pike and Jyrki Alakuijala
  22. //
  23. // http://code.google.com/p/cityhash/
  24. //
  25. // This file provides a few functions for hashing strings. All of them are
  26. // high-quality functions in the sense that they pass standard tests such
  27. // as Austin Appleby's SMHasher. They are also fast.
  28. //
  29. // For 64-bit x86 code, on short strings, we don't know of anything faster than
  30. // CityHash64 that is of comparable quality. We believe our nearest competitor
  31. // is Murmur3. For 64-bit x86 code, CityHash64 is an excellent choice for hash
  32. // tables and most other hashing (excluding cryptography).
  33. //
  34. // For 64-bit x86 code, on long strings, the picture is more complicated.
  35. // On many recent Intel CPUs, such as Nehalem, Westmere, Sandy Bridge, etc.,
  36. // CityHashCrc128 appears to be faster than all competitors of comparable
  37. // quality. CityHash128 is also good but not quite as fast. We believe our
  38. // nearest competitor is Bob Jenkins' Spooky. We don't have great data for
  39. // other 64-bit CPUs, but for long strings we know that Spooky is slightly
  40. // faster than CityHash on some relatively recent AMD x86-64 CPUs, for example.
  41. // Note that CityHashCrc128 is declared in citycrc.h.
  42. //
  43. // For 32-bit x86 code, we don't know of anything faster than CityHash32 that
  44. // is of comparable quality. We believe our nearest competitor is Murmur3A.
  45. // (On 64-bit CPUs, it is typically faster to use the other CityHash variants.)
  46. //
  47. // Functions in the CityHash family are not suitable for cryptography.
  48. //
  49. // Please see CityHash's README file for more details on our performance
  50. // measurements and so on.
  51. //
  52. // WARNING: This code has been only lightly tested on big-endian platforms!
  53. // It is known to work well on little-endian platforms that have a small penalty
  54. // for unaligned reads, such as current Intel and AMD moderate-to-high-end CPUs.
  55. // It should work on all 32-bit and 64-bit platforms that allow unaligned reads;
  56. // bug reports are welcome.
  57. //
  58. // By the way, for some hash functions, given strings a and b, the hash
  59. // of a+b is easily derived from the hashes of a and b. This property
  60. // doesn't hold for any hash functions in this file.
  61. #ifndef CITY_HASH_H_
  62. #define CITY_HASH_H_
  63. #include <stdlib.h> // for size_t.
  64. #include <stdint.h>
  65. #include <utility>
  66. typedef uint8_t uint8;
  67. typedef uint32_t uint32;
  68. typedef uint64_t uint64;
  69. typedef std::pair<uint64, uint64> uint128;
  70. inline uint64 Uint128Low64(const uint128& x) { return x.first; }
  71. inline uint64 Uint128High64(const uint128& x) { return x.second; }
  72. // Hash function for a byte array.
  73. uint64 CityHash64(const char *buf, size_t len);
  74. // Hash function for a byte array. For convenience, a 64-bit seed is also
  75. // hashed into the result.
  76. uint64 CityHash64WithSeed(const char *buf, size_t len, uint64 seed);
  77. // Hash function for a byte array. For convenience, two seeds are also
  78. // hashed into the result.
  79. uint64 CityHash64WithSeeds(const char *buf, size_t len,
  80. uint64 seed0, uint64 seed1);
  81. // Hash function for a byte array.
  82. uint128 CityHash128(const char *s, size_t len);
  83. // Hash function for a byte array. For convenience, a 128-bit seed is also
  84. // hashed into the result.
  85. uint128 CityHash128WithSeed(const char *s, size_t len, uint128 seed);
  86. // Hash function for a byte array. Most useful in 32-bit binaries.
  87. uint32 CityHash32(const char *buf, size_t len);
  88. // Hash 128 input bits down to 64 bits of output.
  89. // This is intended to be a reasonably good hash function.
  90. inline uint64 Hash128to64(const uint128& x) {
  91. // Murmur-inspired hashing.
  92. const uint64 kMul = 0x9ddfea08eb382d69ULL;
  93. uint64 a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
  94. a ^= (a >> 47);
  95. uint64 b = (Uint128High64(x) ^ a) * kMul;
  96. b ^= (b >> 47);
  97. b *= kMul;
  98. return b;
  99. }
  100. #endif // CITY_HASH_H_