FastqPuri
city.h
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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 //
42 // For 32-bit x86 code, we don't know of anything faster than CityHash32 that
43 // is of comparable quality. We believe our nearest competitor is Murmur3A.
44 // (On 64-bit CPUs, it is typically faster to use the other CityHash variants.)
45 //
46 // Functions in the CityHash family are not suitable for cryptography.
47 //
48 // WARNING: This code has been only lightly tested on big-endian platforms!
49 // It is known to work well on little-endian platforms that have a small penalty
50 // for unaligned reads, such as current Intel and AMD moderate-to-high-end CPUs.
51 // It should work on all 32-bit and 64-bit platforms that allow unaligned reads;
52 // bug reports are welcome.
53 //
54 // By the way, for some hash functions, given strings a and b, the hash
55 // of a+b is easily derived from the hashes of a and b. This property
56 // doesn't hold for any hash functions in this file.
57 
67 #ifndef CITY_HASH_H_
68 #define CITY_HASH_H_
69 
70 #include <stdlib.h> // for size_t.
71 #include <stdint.h>
72 
73 
74 
75 typedef uint8_t uint8;
76 typedef uint16_t uint16;
77 typedef uint32_t uint32;
78 typedef uint64_t uint64;
79 
80 typedef struct _uint128 uint128;
81 struct _uint128 {
82  uint64 first;
83  uint64 second;
84 };
85 
86 #define Uint128Low64(x) (x).first
87 #define Uint128High64(x) (x).second
88 
89 //inline uint64_t Uint128Low64(const uint128& x) { return x.first; }
90 //inline uint64_t Uint128High64(const uint128& x) { return x.second; }
91 
92 // Hash function for a byte array.
93 uint64_t CityHash64(const char *buf, size_t len);
94 
95 // Hash function for a byte array. For convenience, a 64-bit seed is also
96 // hashed into the result.
97 uint64_t CityHash64WithSeed(const char *buf, size_t len, uint64_t seed);
98 
99 // Hash function for a byte array. For convenience, two seeds are also
100 // hashed into the result.
101 uint64_t CityHash64WithSeeds(const char *buf, size_t len,
102  uint64_t seed0, uint64_t seed1);
103 
104 // Hash function for a byte array.
105 uint128 CityHash128(const char *s, size_t len);
106 
107 // Hash function for a byte array. For convenience, a 128-bit seed is also
108 // hashed into the result.
109 uint128 CityHash128WithSeed(const char *s, size_t len, uint128 seed);
110 
111 // Hash function for a byte array. Most useful in 32-bit binaries.
112 uint32 CityHash32(const char *buf, size_t len);
113 
114 // Hash 128 input bits down to 64 bits of output.
115 // This is intended to be a reasonably good hash function.
116 static inline uint64_t Hash128to64(const uint128 x) {
117  // Murmur-inspired hashing.
118  const uint64_t kMul = 0x9ddfea08eb382d69ULL;
119  uint64_t a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
120  a ^= (a >> 47);
121  uint64_t b = (Uint128High64(x) ^ a) * kMul;
122  b ^= (b >> 47);
123  b *= kMul;
124  return b;
125 }
126 
127 #endif // CITY_HASH_H_
Definition: city.h:81