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 // 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.
28 //
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().
32 //
33 // Functions in the CityHash family are not suitable for cryptography.
34 //
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.
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 BASE_THIRD_PARTY_CITYHASH_V103_SRC_CITY_V103_H_
44 #define BASE_THIRD_PARTY_CITYHASH_V103_SRC_CITY_V103_H_
45
46 #include <stdint.h>
47 #include <stdlib.h> // for size_t.
48 #include <utility>
49
50 namespace base {
51 namespace internal {
52 namespace cityhash_v103 {
53
54 typedef uint8_t uint8;
55 typedef uint32_t uint32;
56 typedef uint64_t uint64;
57 typedef std::pair<uint64, uint64> uint128;
58
Uint128Low64(const uint128 & x)59 inline uint64 Uint128Low64(const uint128& x) {
60 return x.first;
61 }
Uint128High64(const uint128 & x)62 inline uint64 Uint128High64(const uint128& x) {
63 return x.second;
64 }
65
66 // Hash function for a byte array.
67 uint64 CityHash64(const char* buf, size_t len);
68
69 // Hash function for a byte array. For convenience, a 64-bit seed is also
70 // hashed into the result.
71 uint64 CityHash64WithSeed(const char* buf, size_t len, uint64 seed);
72
73 // Hash function for a byte array. For convenience, two seeds are also
74 // hashed into the result.
75 uint64 CityHash64WithSeeds(const char* buf,
76 size_t len,
77 uint64 seed0,
78 uint64 seed1);
79
80 // Hash function for a byte array.
81 uint128 CityHash128(const char* s, size_t len);
82
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
87 // Hash 128 input bits down to 64 bits of output.
88 // This is intended to be a reasonably good hash function.
Hash128to64(const uint128 & x)89 inline uint64 Hash128to64(const uint128& x) {
90 // Murmur-inspired hashing.
91 const uint64 kMul = 0x9ddfea08eb382d69ULL;
92 uint64 a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
93 a ^= (a >> 47);
94 uint64 b = (Uint128High64(x) ^ a) * kMul;
95 b ^= (b >> 47);
96 b *= kMul;
97 return b;
98 }
99
100 } // namespace cityhash_v103
101 } // namespace internal
102 } // namespace base
103
104 #endif // BASE_THIRD_PARTY_CITYHASH_V103_SRC_CITY_V103_H_
105