104 lines
3.1 KiB
C
104 lines
3.1 KiB
C
/*
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* copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
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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_crc32
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* Public header for CRC hash function implementation.
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*/
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#ifndef AVUTIL_CRC_H
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#define AVUTIL_CRC_H
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#include <stdint.h>
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#include <stddef.h>
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#include "attributes.h"
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#include "version.h"
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/**
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* @defgroup lavu_crc32 CRC
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* @ingroup lavu_hash
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* CRC (Cyclic Redundancy Check) hash function implementation.
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*
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* This module supports numerous CRC polynomials, in addition to the most
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* widely used CRC-32-IEEE. See @ref AVCRCId for a list of available
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* polynomials.
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*
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* @{
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*/
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typedef uint32_t AVCRC;
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typedef enum {
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AV_CRC_8_ATM,
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AV_CRC_16_ANSI,
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AV_CRC_16_CCITT,
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AV_CRC_32_IEEE,
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AV_CRC_32_IEEE_LE, /*< reversed bitorder version of AV_CRC_32_IEEE */
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AV_CRC_16_ANSI_LE, /*< reversed bitorder version of AV_CRC_16_ANSI */
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#if FF_API_CRC_BIG_TABLE
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AV_CRC_24_IEEE = 12,
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#else
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AV_CRC_24_IEEE,
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#endif /* FF_API_CRC_BIG_TABLE */
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AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */
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}AVCRCId;
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/**
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* Initialize a CRC table.
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* @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
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* @param le If 1, the lowest bit represents the coefficient for the highest
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* exponent of the corresponding polynomial (both for poly and
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* actual CRC).
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* If 0, you must swap the CRC parameter and the result of av_crc
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* if you need the standard representation (can be simplified in
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* most cases to e.g. bswap16):
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* av_bswap32(crc << (32-bits))
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* @param bits number of bits for the CRC
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* @param poly generator polynomial without the x**bits coefficient, in the
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* representation as specified by le
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* @param ctx_size size of ctx in bytes
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* @return <0 on failure
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*/
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int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
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/**
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* Get an initialized standard CRC table.
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* @param crc_id ID of a standard CRC
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* @return a pointer to the CRC table or NULL on failure
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*/
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const AVCRC *av_crc_get_table(AVCRCId crc_id);
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/**
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* Calculate the CRC of a block.
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* @param crc CRC of previous blocks if any or initial value for CRC
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* @return CRC updated with the data from the given block
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*
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* @see av_crc_init() "le" parameter
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*/
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uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
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const uint8_t *buffer, size_t length) av_pure;
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/**
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* @}
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*/
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#endif /* AVUTIL_CRC_H */
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