crc.h 2.53 KB
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/*
 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
 * 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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 * Libav is distributed in the hope that it will be useful,
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 * 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
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 * License along with Libav; 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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#ifndef AVUTIL_CRC_H
#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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typedef uint32_t AVCRC;

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typedef enum {
    AV_CRC_8_ATM,
    AV_CRC_16_ANSI,
    AV_CRC_16_CCITT,
    AV_CRC_32_IEEE,
    AV_CRC_32_IEEE_LE,  /*< reversed bitorder version of AV_CRC_32_IEEE */
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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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/**
 * Initialize a CRC table.
 * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
 * @param le If 1, the lowest bit represents the coefficient for the highest
 *           exponent of the corresponding polynomial (both for poly and
 *           actual CRC).
 *           If 0, you must swap the CRC parameter and the result of av_crc
 *           if you need the standard representation (can be simplified in
 *           most cases to e.g. bswap16):
 *           av_bswap32(crc << (32-bits))
 * @param bits number of bits for the CRC
 * @param poly generator polynomial without the x**bits coefficient, in the
 *             representation as specified by le
 * @param ctx_size size of ctx in bytes
 * @return <0 on failure
 */
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int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
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/**
 * Get an initialized standard CRC table.
 * @param crc_id ID of a standard CRC
 * @return a pointer to the CRC table or NULL on failure
 */
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const AVCRC *av_crc_get_table(AVCRCId crc_id);
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/**
 * Calculate the CRC of a block.
 * @param crc CRC of previous blocks if any or initial value for CRC
 * @return CRC updated with the data from the given block
 *
 * @see av_crc_init() "le" parameter
 */
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uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
                const uint8_t *buffer, size_t length) av_pure;
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#endif /* AVUTIL_CRC_H */