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 */ 69 struct 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 */ 81 void 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 */ 94 void 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 104 void av_murmur3_update(struct AVMurMur3 *c, const uint8_t *src, int len); 105 #else 106 void 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 */ 115 void av_murmur3_final(struct AVMurMur3 *c, uint8_t dst[16]); 116 117 /** 118 * @} 119 */ 120 121 #endif /* AVUTIL_MURMUR3_H */ 122