1
// Copyright (c) 2011 Google, Inc.
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:
10
// The above copyright notice and this permission notice shall be included in
11
// all copies or substantial portions of the Software.
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
21
// CityHash, by Geoff Pike and Jyrki Alakuijala
23
// This file provides a few functions for hashing strings. On x86-64
24
// hardware in 2011, CityHash64() is faster than other high-quality
25
// hash functions, such as Murmur. This is largely due to higher
26
// instruction-level parallelism. CityHash64() and CityHash128() also perform
27
// well on hash-quality tests.
29
// CityHash128() is optimized for relatively long strings and returns
30
// a 128-bit hash. For strings more than about 2000 bytes it can be
31
// faster than CityHash64().
33
// Functions in the CityHash family are not suitable for cryptography.
35
// WARNING: This code has not been tested on big-endian platforms!
36
// It is known to work well on little-endian platforms that have a small penalty
37
// for unaligned reads, such as current Intel and AMD moderate-to-high-end CPUs.
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.
46
#include <stdlib.h> // for size_t.
50
typedef uint8_t uint8;
51
typedef uint32_t uint32;
52
typedef uint64_t uint64;
53
typedef std::pair<uint64, uint64> uint128;
55
inline uint64 Uint128Low64(const uint128& x) { return x.first; }
56
inline uint64 Uint128High64(const uint128& x) { return x.second; }
58
// Hash function for a byte array.
59
uint64 CityHash64(const char *buf, size_t len);
61
// Hash function for a byte array. For convenience, a 64-bit seed is also
62
// hashed into the result.
63
uint64 CityHash64WithSeed(const char *buf, size_t len, uint64 seed);
65
// Hash function for a byte array. For convenience, two seeds are also
66
// hashed into the result.
67
uint64 CityHash64WithSeeds(const char *buf, size_t len,
68
uint64 seed0, uint64 seed1);
70
// Hash function for a byte array.
71
uint128 CityHash128(const char *s, size_t len);
73
// Hash function for a byte array. For convenience, a 128-bit seed is also
74
// hashed into the result.
75
uint128 CityHash128WithSeed(const char *s, size_t len, uint128 seed);
77
// Hash 128 input bits down to 64 bits of output.
78
// This is intended to be a reasonably good hash function.
79
inline uint64 Hash128to64(const uint128& x) {
80
// Murmur-inspired hashing.
81
const uint64 kMul = 0x9ddfea08eb382d69ULL;
82
uint64 a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
84
uint64 b = (Uint128High64(x) ^ a) * kMul;
90
#endif // CITY_HASH_H_