/* * Copyright (C) 2013 Reimar Döffinger <Reimar.Doeffinger@gmx.de> * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * @ingroup lavu_murmur3 * Public header for MurmurHash3 hash function implementation. */ #ifndef AVUTIL_MURMUR3_H #define AVUTIL_MURMUR3_H #include <stdint.h> /** * @defgroup lavu_murmur3 Murmur3 * @ingroup lavu_hash * MurmurHash3 hash function implementation. * * MurmurHash3 is a non-cryptographic hash function, of which three * incompatible versions were created by its inventor Austin Appleby: * * - 32-bit output * - 128-bit output for 32-bit platforms * - 128-bit output for 64-bit platforms * * FFmpeg only implements the last variant: 128-bit output designed for 64-bit * platforms. Even though the hash function was designed for 64-bit platforms, * the function in reality works on 32-bit systems too, only with reduced * performance. * * @anchor lavu_murmur3_seedinfo * By design, MurmurHash3 requires a seed to operate. In response to this, * libavutil provides two functions for hash initiation, one that requires a * seed (av_murmur3_init_seeded()) and one that uses a fixed arbitrary integer * as the seed, and therefore does not (av_murmur3_init()). * * To make hashes comparable, you should provide the same seed for all calls to * this hash function -- if you are supplying one yourself, that is. * * @{ */ /** * Allocate an AVMurMur3 hash context. * * @return Uninitialized hash context or `NULL` in case of error */ struct AVMurMur3 *av_murmur3_alloc(void); /** * Initialize or reinitialize an AVMurMur3 hash context with a seed. * * @param[out] c Hash context * @param[in] seed Random seed * * @see av_murmur3_init() * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of * seeds for MurmurHash3. */ void av_murmur3_init_seeded(struct AVMurMur3 *c, uint64_t seed); /** * Initialize or reinitialize an AVMurMur3 hash context. * * Equivalent to av_murmur3_init_seeded() with a built-in seed. * * @param[out] c Hash context * * @see av_murmur3_init_seeded() * @see @ref lavu_murmur3_seedinfo "Detailed description" on a discussion of * seeds for MurmurHash3. */ void av_murmur3_init(struct AVMurMur3 *c); /** * Update hash context with new data. * * @param[out] c Hash context * @param[in] src Input data to update hash with * @param[in] len Number of bytes to read from `src` */ void av_murmur3_update(struct AVMurMur3 *c, const uint8_t *src, int len); /** * Finish hashing and output digest value. * * @param[in,out] c Hash context * @param[out] dst Buffer where output digest value is stored */ void av_murmur3_final(struct AVMurMur3 *c, uint8_t dst[16]); /** * @} */ #endif /* AVUTIL_MURMUR3_H */