/* * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at> * * 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 * 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 * 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" /** * @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_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 */ AV_CRC_16_ANSI_LE, /*< reversed bitorder version of AV_CRC_16_ANSI */ AV_CRC_24_IEEE, AV_CRC_8_EBU, AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */ }AVCRCId; /** * 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 ctx initialized AVCRC array (see av_crc_init()) * @param crc CRC of previous blocks if any or initial value for CRC * @param buffer buffer whose CRC to calculate * @param length length of the buffer * @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 */