2 * Copyright (C) 2013 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
4 * This file is part of FFmpeg.
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.
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.
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
23 * @ingroup lavu_murmur3
24 * Public header for MurmurHash3 hash function implementation.
27 #ifndef AVUTIL_MURMUR3_H
28 #define AVUTIL_MURMUR3_H
36 * @defgroup lavu_murmur3 Murmur3
38 * MurmurHash3 hash function implementation.
40 * MurmurHash3 is a non-cryptographic hash function, of which three
41 * incompatible versions were created by its inventor Austin Appleby:
44 * - 128-bit output for 32-bit platforms
45 * - 128-bit output for 64-bit platforms
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
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()).
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.
65 * Allocate an AVMurMur3 hash context.
67 * @return Uninitialized hash context or `NULL` in case of error
69 struct AVMurMur3 *av_murmur3_alloc(void);
72 * Initialize or reinitialize an AVMurMur3 hash context with a seed.
74 * @param[out] c Hash context
75 * @param[in] seed Random seed
77 * @see av_murmur3_init()
78 * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of
79 * seeds for MurmurHash3.
81 void av_murmur3_init_seeded(struct AVMurMur3 *c, uint64_t seed);
84 * Initialize or reinitialize an AVMurMur3 hash context.
86 * Equivalent to av_murmur3_init_seeded() with a built-in seed.
88 * @param[out] c Hash context
90 * @see av_murmur3_init_seeded()
91 * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of
92 * seeds for MurmurHash3.
94 void av_murmur3_init(struct AVMurMur3 *c);
97 * Update hash context with new data.
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`
103 #if FF_API_CRYPTO_SIZE_T
104 void av_murmur3_update(struct AVMurMur3 *c, const uint8_t *src, int len);
106 void av_murmur3_update(struct AVMurMur3 *c, const uint8_t *src, size_t len);
110 * Finish hashing and output digest value.
112 * @param[in,out] c Hash context
113 * @param[out] dst Buffer where output digest value is stored
115 void av_murmur3_final(struct AVMurMur3 *c, uint8_t dst[16]);
121 #endif /* AVUTIL_MURMUR3_H */