FFmpeg 4.2.2
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 <stdint.h>
31
32#include "version.h"
33
34/**
35 * @defgroup lavu_murmur3 Murmur3
36 * @ingroup lavu_hash
37 * MurmurHash3 hash function implementation.
38 *
39 * MurmurHash3 is a non-cryptographic hash function, of which three
40 * incompatible versions were created by its inventor Austin Appleby:
41 *
42 * - 32-bit output
43 * - 128-bit output for 32-bit platforms
44 * - 128-bit output for 64-bit platforms
45 *
46 * FFmpeg only implements the last variant: 128-bit output designed for 64-bit
47 * platforms. Even though the hash function was designed for 64-bit platforms,
48 * the function in reality works on 32-bit systems too, only with reduced
49 * performance.
50 *
51 * @anchor lavu_murmur3_seedinfo
52 * By design, MurmurHash3 requires a seed to operate. In response to this,
53 * libavutil provides two functions for hash initiation, one that requires a
54 * seed (av_murmur3_init_seeded()) and one that uses a fixed arbitrary integer
55 * as the seed, and therefore does not (av_murmur3_init()).
56 *
57 * To make hashes comparable, you should provide the same seed for all calls to
58 * this hash function -- if you are supplying one yourself, that is.
59 *
60 * @{
61 */
62
63/**
64 * Allocate an AVMurMur3 hash context.
65 *
66 * @return Uninitialized hash context or `NULL` in case of error
67 */
68struct AVMurMur3 *av_murmur3_alloc(void);
69
70/**
71 * Initialize or reinitialize an AVMurMur3 hash context with a seed.
72 *
73 * @param[out] c Hash context
74 * @param[in] seed Random seed
75 *
76 * @see av_murmur3_init()
77 * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of
78 * seeds for MurmurHash3.
79 */
80void av_murmur3_init_seeded(struct AVMurMur3 *c, uint64_t seed);
81
82/**
83 * Initialize or reinitialize an AVMurMur3 hash context.
84 *
85 * Equivalent to av_murmur3_init_seeded() with a built-in seed.
86 *
87 * @param[out] c Hash context
88 *
89 * @see av_murmur3_init_seeded()
90 * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of
91 * seeds for MurmurHash3.
92 */
93void av_murmur3_init(struct AVMurMur3 *c);
94
95/**
96 * Update hash context with new data.
97 *
98 * @param[out] c Hash context
99 * @param[in] src Input data to update hash with
100 * @param[in] len Number of bytes to read from `src`
101 */
102#if FF_API_CRYPTO_SIZE_T
103void av_murmur3_update(struct AVMurMur3 *c, const uint8_t *src, int len);
104#else
105void av_murmur3_update(struct AVMurMur3 *c, const uint8_t *src, size_t len);
106#endif
107
108/**
109 * Finish hashing and output digest value.
110 *
111 * @param[in,out] c Hash context
112 * @param[out] dst Buffer where output digest value is stored
113 */
114void av_murmur3_final(struct AVMurMur3 *c, uint8_t dst[16]);
115
116/**
117 * @}
118 */
119
120#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, int 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.
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