FFmpeg 4.4.5
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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#include "version.h"
34
35/**
36 * @defgroup lavu_murmur3 Murmur3
37 * @ingroup lavu_hash
38 * MurmurHash3 hash function implementation.
39 *
40 * MurmurHash3 is a non-cryptographic hash function, of which three
41 * incompatible versions were created by its inventor Austin Appleby:
42 *
43 * - 32-bit output
44 * - 128-bit output for 32-bit platforms
45 * - 128-bit output for 64-bit platforms
46 *
47 * FFmpeg only implements the last variant: 128-bit output designed for 64-bit
48 * platforms. Even though the hash function was designed for 64-bit platforms,
49 * the function in reality works on 32-bit systems too, only with reduced
50 * performance.
51 *
52 * @anchor lavu_murmur3_seedinfo
53 * By design, MurmurHash3 requires a seed to operate. In response to this,
54 * libavutil provides two functions for hash initiation, one that requires a
55 * seed (av_murmur3_init_seeded()) and one that uses a fixed arbitrary integer
56 * as the seed, and therefore does not (av_murmur3_init()).
57 *
58 * To make hashes comparable, you should provide the same seed for all calls to
59 * this hash function -- if you are supplying one yourself, that is.
60 *
61 * @{
62 */
63
64/**
65 * Allocate an AVMurMur3 hash context.
66 *
67 * @return Uninitialized hash context or `NULL` in case of error
68 */
69struct AVMurMur3 *av_murmur3_alloc(void);
70
71/**
72 * Initialize or reinitialize an AVMurMur3 hash context with a seed.
73 *
74 * @param[out] c Hash context
75 * @param[in] seed Random seed
76 *
77 * @see av_murmur3_init()
78 * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of
79 * seeds for MurmurHash3.
80 */
81void av_murmur3_init_seeded(struct AVMurMur3 *c, uint64_t seed);
82
83/**
84 * Initialize or reinitialize an AVMurMur3 hash context.
85 *
86 * Equivalent to av_murmur3_init_seeded() with a built-in seed.
87 *
88 * @param[out] c Hash context
89 *
90 * @see av_murmur3_init_seeded()
91 * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of
92 * seeds for MurmurHash3.
93 */
94void av_murmur3_init(struct AVMurMur3 *c);
95
96/**
97 * Update hash context with new data.
98 *
99 * @param[out] c Hash context
100 * @param[in] src Input data to update hash with
101 * @param[in] len Number of bytes to read from `src`
102 */
103#if FF_API_CRYPTO_SIZE_T
104void av_murmur3_update(struct AVMurMur3 *c, const uint8_t *src, int len);
105#else
106void av_murmur3_update(struct AVMurMur3 *c, const uint8_t *src, size_t len);
107#endif
108
109/**
110 * Finish hashing and output digest value.
111 *
112 * @param[in,out] c Hash context
113 * @param[out] dst Buffer where output digest value is stored
114 */
115void av_murmur3_final(struct AVMurMur3 *c, uint8_t dst[16]);
116
117/**
118 * @}
119 */
120
121#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.
swscale version macros