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