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115 lines
3.4 KiB
C
115 lines
3.4 KiB
C
/*
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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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