blob: 47e22b4c7872ba1c623aa0b30bdb4bce9bb7c65e [file] [log] [blame]
* copyright (c) 2006 Michael Niedermayer <>
* 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
* 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_crc32
* Public header for CRC hash function implementation.
#ifndef AVUTIL_CRC_H
#define AVUTIL_CRC_H
#include <stdint.h>
#include <stddef.h>
#include "attributes.h"
#include "version.h"
* @defgroup lavu_crc32 CRC
* @ingroup lavu_hash
* CRC (Cyclic Redundancy Check) hash function implementation.
* This module supports numerous CRC polynomials, in addition to the most
* widely used CRC-32-IEEE. See @ref AVCRCId for a list of available
* polynomials.
* @{
typedef uint32_t AVCRC;
typedef enum {
AV_CRC_32_IEEE_LE, /*< reversed bitorder version of AV_CRC_32_IEEE */
AV_CRC_16_ANSI_LE, /*< reversed bitorder version of AV_CRC_16_ANSI */
AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */
* 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
int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
* 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
const AVCRC *av_crc_get_table(AVCRCId crc_id);
* 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
uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
const uint8_t *buffer, size_t length) av_pure;
* @}
#endif /* AVUTIL_CRC_H */