FFmpeg 5.1.4
murmur3.h
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1/*
2 * Copyright (C) 2013 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
3 *
4 * This file is part of FFmpeg.
5 *
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * FFmpeg 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 GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21/**
22 * @file
23 * @ingroup lavu_murmur3
24 * Public header for MurmurHash3 hash function implementation.
25 */
26
27#ifndef AVUTIL_MURMUR3_H
28#define AVUTIL_MURMUR3_H
29
30#include <stddef.h>
31#include <stdint.h>
32
33/**
34 * @defgroup lavu_murmur3 Murmur3
35 * @ingroup lavu_hash
36 * MurmurHash3 hash function implementation.
37 *
38 * MurmurHash3 is a non-cryptographic hash function, of which three
39 * incompatible versions were created by its inventor Austin Appleby:
40 *
41 * - 32-bit output
42 * - 128-bit output for 32-bit platforms
43 * - 128-bit output for 64-bit platforms
44 *
45 * FFmpeg only implements the last variant: 128-bit output designed for 64-bit
46 * platforms. Even though the hash function was designed for 64-bit platforms,
47 * the function in reality works on 32-bit systems too, only with reduced
48 * performance.
49 *
50 * @anchor lavu_murmur3_seedinfo
51 * By design, MurmurHash3 requires a seed to operate. In response to this,
52 * libavutil provides two functions for hash initiation, one that requires a
53 * seed (av_murmur3_init_seeded()) and one that uses a fixed arbitrary integer
54 * as the seed, and therefore does not (av_murmur3_init()).
55 *
56 * To make hashes comparable, you should provide the same seed for all calls to
57 * this hash function -- if you are supplying one yourself, that is.
58 *
59 * @{
60 */
61
62/**
63 * Allocate an AVMurMur3 hash context.
64 *
65 * @return Uninitialized hash context or `NULL` in case of error
66 */
67struct AVMurMur3 *av_murmur3_alloc(void);
68
69/**
70 * Initialize or reinitialize an AVMurMur3 hash context with a seed.
71 *
72 * @param[out] c Hash context
73 * @param[in] seed Random seed
74 *
75 * @see av_murmur3_init()
76 * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of
77 * seeds for MurmurHash3.
78 */
79void av_murmur3_init_seeded(struct AVMurMur3 *c, uint64_t seed);
80
81/**
82 * Initialize or reinitialize an AVMurMur3 hash context.
83 *
84 * Equivalent to av_murmur3_init_seeded() with a built-in seed.
85 *
86 * @param[out] c Hash context
87 *
88 * @see av_murmur3_init_seeded()
89 * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of
90 * seeds for MurmurHash3.
91 */
92void av_murmur3_init(struct AVMurMur3 *c);
93
94/**
95 * Update hash context with new data.
96 *
97 * @param[out] c Hash context
98 * @param[in] src Input data to update hash with
99 * @param[in] len Number of bytes to read from `src`
100 */
101void av_murmur3_update(struct AVMurMur3 *c, const uint8_t *src, size_t len);
102
103/**
104 * Finish hashing and output digest value.
105 *
106 * @param[in,out] c Hash context
107 * @param[out] dst Buffer where output digest value is stored
108 */
109void av_murmur3_final(struct AVMurMur3 *c, uint8_t dst[16]);
110
111/**
112 * @}
113 */
114
115#endif /* AVUTIL_MURMUR3_H */
struct AVMurMur3 * av_murmur3_alloc(void)
Allocate an AVMurMur3 hash context.
void av_murmur3_update(struct AVMurMur3 *c, const uint8_t *src, size_t len)
Update hash context with new data.
void av_murmur3_init(struct AVMurMur3 *c)
Initialize or reinitialize an AVMurMur3 hash context.
void av_murmur3_init_seeded(struct AVMurMur3 *c, uint64_t seed)
Initialize or reinitialize an AVMurMur3 hash context with a seed.
void av_murmur3_final(struct AVMurMur3 *c, uint8_t dst[16])
Finish hashing and output digest value.