1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
3 *
4 * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
20 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #include "cx/hash_key.h"
30 #include <string.h>
31
32 void cx_hash_murmur(CxHashKey *key) {
33 unsigned char const *data = key->data;
34 if (data == NULL) {
35 // extension: special value for NULL
36 key->hash = 1574210520u;
37 return;
38 }
39 size_t len = key->len;
40
41 unsigned m = 0x5bd1e995;
42 unsigned r = 24;
43 unsigned h = 25 ^ len;
44 unsigned i = 0;
45 while (len >= 4) {
46 unsigned k = data[i + 0] & 0xFF;
47 k |= (data[i + 1] & 0xFF) << 8;
48 k |= (data[i + 2] & 0xFF) << 16;
49 k |= (data[i + 3] & 0xFF) << 24;
50
51 k *= m;
52 k ^= k >> r;
53 k *= m;
54
55 h *= m;
56 h ^= k;
57
58 i += 4;
59 len -= 4;
60 }
61
62 switch (len) {
63 case 3:
64 h ^= (data[i + 2] & 0xFF) << 16;
65 __attribute__((__fallthrough__));
66 case 2:
67 h ^= (data[i + 1] & 0xFF) << 8;
68 __attribute__((__fallthrough__));
69 case 1:
70 h ^= (data[i + 0] & 0xFF);
71 h *= m;
72 __attribute__((__fallthrough__));
73 default: // do nothing
74 ;
75 }
76
77 h ^= h >> 13;
78 h *= m;
79 h ^= h >> 15;
80
81 key->hash = h;
82 }
83
84 CxHashKey cx_hash_key_str(char const *str) {
85 CxHashKey key;
86 key.data = str;
87 key.len = str == NULL ? 0 : strlen(str);
88 cx_hash_murmur(&key);
89 return key;
90 }
91
92 CxHashKey cx_hash_key_bytes(
93 unsigned char const *bytes,
94 size_t len
95 ) {
96 CxHashKey key;
97 key.data = bytes;
98 key.len = len;
99 cx_hash_murmur(&key);
100 return key;
101 }
102
103 CxHashKey cx_hash_key(
104 void const *obj,
105 size_t len
106 ) {
107 CxHashKey key;
108 key.data = obj;
109 key.len = len;
110 cx_hash_murmur(&key);
111 return key;
112 }
113