src/hash_key.c

changeset 563
69a83fad8a35
child 603
c49104015a6b
equal deleted inserted replaced
562:fd3368c20413 563:69a83fad8a35
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 size_t len = key->len;
34 unsigned char const *data = key->data.cbytes;
35
36 unsigned m = 0x5bd1e995;
37 unsigned r = 24;
38 unsigned h = 25 ^ len;
39 unsigned i = 0;
40 while (len >= 4) {
41 unsigned k = data[i + 0] & 0xFF;
42 k |= (data[i + 1] & 0xFF) << 8;
43 k |= (data[i + 2] & 0xFF) << 16;
44 k |= (data[i + 3] & 0xFF) << 24;
45
46 k *= m;
47 k ^= k >> r;
48 k *= m;
49
50 h *= m;
51 h ^= k;
52
53 i += 4;
54 len -= 4;
55 }
56
57 switch (len) {
58 case 3:
59 h ^= (data[i + 2] & 0xFF) << 16;
60 __attribute__((__fallthrough__));
61 case 2:
62 h ^= (data[i + 1] & 0xFF) << 8;
63 __attribute__((__fallthrough__));
64 case 1:
65 h ^= (data[i + 0] & 0xFF);
66 h *= m;
67 __attribute__((__fallthrough__));
68 default:
69 /* do nothing */;
70 }
71
72 h ^= h >> 13;
73 h *= m;
74 h ^= h >> 15;
75
76 key->hash = h;
77 }
78
79 CxHashKey cx_hash_key_str(char const *str) {
80 CxHashKey key;
81 key.data.cstr = str;
82 key.len = str == NULL ? 0 : (1 + strlen(str));
83 cx_hash_murmur(&key);
84 return key;
85 }
86
87 CxHashKey cx_hash_key_bytes(
88 unsigned char const *bytes,
89 size_t len
90 ) {
91 CxHashKey key;
92 key.data.cbytes = bytes;
93 key.len = len;
94 cx_hash_murmur(&key);
95 return key;
96 }
97
98 CxHashKey cx_hash_key(
99 void *obj,
100 size_t len
101 ) {
102 CxHashKey key;
103 key.data.obj = obj;
104 key.len = len;
105 cx_hash_murmur(&key);
106 return key;
107 }

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