0f92d0b0e405f9ebd6b161ce9e05c5ec6b6c3257
[mesa.git] / src / util / fnv1a.h
1 /*
2 * Copyright © 2009,2012 Intel Corporation
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 *
23 * Authors:
24 * Eric Anholt <eric@anholt.net>
25 *
26 */
27
28 #ifndef _FNV1A_H
29 #define _FNV1A_H
30
31 enum {
32 _mesa_fnv32_1a_offset_bias = 2166136261u,
33 };
34
35 /**
36 * Quick FNV-1a hash implementation based on:
37 * http://www.isthe.com/chongo/tech/comp/fnv/
38 *
39 * FNV-1a is not be the best hash out there -- Jenkins's lookup3 is supposed
40 * to be quite good, and it probably beats FNV. But FNV has the advantage
41 * that it involves almost no code. For an improvement on both, see Paul
42 * Hsieh's http://www.azillionmonkeys.com/qed/hash.html
43 */
44 static inline uint32_t
45 _mesa_fnv32_1a_accumulate_block(uint32_t hash, const void *data, size_t size)
46 {
47 const uint8_t *bytes = (const uint8_t *)data;
48
49 while (size-- != 0) {
50 hash ^= *bytes;
51 hash = hash * 0x01000193;
52 bytes++;
53 }
54
55 return hash;
56 }
57
58 #define _mesa_fnv32_1a_accumulate(hash, expr) \
59 _mesa_fnv32_1a_accumulate_block(hash, &(expr), sizeof(expr))
60
61 #endif