1 /*
2 SuperCollider real time audio synthesis system
3 Copyright (c) 2002 James McCartney. All rights reserved.
4 http://www.audiosynth.com
5
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or
9 (at your option) any later version.
10
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21
22 #pragma once
23
24 #include "SC_Types.h"
25 #include "SC_Endian.h"
26
27 // These hash functions are among the best there are in terms of both speed and quality.
28 // A good hash function makes a lot of difference.
29 // I have not used Bob Jenkins own hash function because the keys I use are relatively short.
30
31
32 // hash function for a string
Hash(const char * inKey)33 inline int32 Hash(const char* inKey) {
34 // the one-at-a-time hash.
35 // a very good hash function. ref: a web page by Bob Jenkins.
36 // http://www.burtleburtle.net/bob/hash/doobs.html
37 int32 hash = 0;
38 while (*inKey) {
39 hash += *inKey++;
40 hash += hash << 10;
41 hash ^= hash >> 6;
42 }
43 hash += hash << 3;
44 hash ^= hash >> 11;
45 hash += hash << 15;
46 return hash;
47 }
48
49 // hash function for a string that also returns the length
Hash(const char * inKey,size_t * outLength)50 inline int32 Hash(const char* inKey, size_t* outLength) {
51 // the one-at-a-time hash.
52 // a very good hash function. ref: a web page by Bob Jenkins.
53 const char* origKey = inKey;
54 int32 hash = 0;
55 while (*inKey) {
56 hash += *inKey++;
57 hash += hash << 10;
58 hash ^= hash >> 6;
59 }
60 hash += hash << 3;
61 hash ^= hash >> 11;
62 hash += hash << 15;
63 *outLength = (size_t)(inKey - origKey);
64 return hash;
65 }
66
67 // hash function for an array of char
Hash(const char * inKey,int32 inLength)68 inline int32 Hash(const char* inKey, int32 inLength) {
69 // the one-at-a-time hash.
70 // a very good hash function. ref: a web page by Bob Jenkins.
71 int32 hash = 0;
72 for (int i = 0; i < inLength; ++i) {
73 hash += *inKey++;
74 hash += hash << 10;
75 hash ^= hash >> 6;
76 }
77 hash += hash << 3;
78 hash ^= hash >> 11;
79 hash += hash << 15;
80 return hash;
81 }
82
83 // hash function for integers
Hash(int32 inKey)84 inline int32 Hash(int32 inKey) {
85 // Thomas Wang's integer hash.
86 // http://www.concentric.net/~Ttwang/tech/inthash.htm
87 // a faster hash for integers. also very good.
88 uint32 hash = (uint32)inKey;
89 hash += ~(hash << 15);
90 hash ^= hash >> 10;
91 hash += hash << 3;
92 hash ^= hash >> 6;
93 hash += ~(hash << 11);
94 hash ^= hash >> 16;
95 return (int32)hash;
96 }
97
Hash64(int64 inKey)98 inline int64 Hash64(int64 inKey) {
99 // Thomas Wang's 64 bit integer hash.
100 uint64 hash = (uint64)inKey;
101 hash += ~(hash << 32);
102 hash ^= (hash >> 22);
103 hash += ~(hash << 13);
104 hash ^= (hash >> 8);
105 hash += (hash << 3);
106 hash ^= (hash >> 15);
107 hash += ~(hash << 27);
108 hash ^= (hash >> 31);
109 return (int64)hash;
110 }
111
Hash(const int32 * inKey,int32 inLength)112 inline int32 Hash(const int32* inKey, int32 inLength) {
113 // one-at-a-time hashing of a string of int32's.
114 // uses Thomas Wang's integer hash for the combining step.
115 int32 hash = 0;
116 for (int i = 0; i < inLength; ++i) {
117 hash = Hash(hash + *inKey++);
118 }
119 return hash;
120 }
121
122 #if BYTE_ORDER == LITTLE_ENDIAN
123 const int32 kLASTCHAR = (int32)0xFF000000;
124 #else
125 const int32 kLASTCHAR = (int32)0x000000FF;
126 #endif
127
Hash(const int32 * inKey)128 inline int32 Hash(const int32* inKey) {
129 // hashing of a string of int32's.
130 // uses Thomas Wang's integer hash for the combining step.
131 int32 hash = 0;
132 int32 c;
133 do {
134 c = *inKey++;
135 hash = Hash(hash + c);
136 } while (c & kLASTCHAR);
137 return hash;
138 }
139