1 /* 2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at> 3 * 4 * This file is part of FFmpeg. 5 * 6 * FFmpeg is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU Lesser General Public 8 * License as published by the Free Software Foundation; either 9 * version 2.1 of the License, or (at your option) any later version. 10 * 11 * FFmpeg is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 * Lesser General Public License for more details. 15 * 16 * You should have received a copy of the GNU Lesser General Public 17 * License along with FFmpeg; if not, write to the Free Software 18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 19 */ 20 21 /** 22 * @file 23 * @ingroup lavu_crc32 24 * Public header for CRC hash function implementation. 25 */ 26 27 #ifndef AVUTIL_CRC_H 28 #define AVUTIL_CRC_H 29 30 #include <stdint.h> 31 #include <stddef.h> 32 #include "attributes.h" 33 #include "version.h" 34 35 /** 36 * @defgroup lavu_crc32 CRC 37 * @ingroup lavu_hash 38 * CRC (Cyclic Redundancy Check) hash function implementation. 39 * 40 * This module supports numerous CRC polynomials, in addition to the most 41 * widely used CRC-32-IEEE. See @ref AVCRCId for a list of available 42 * polynomials. 43 * 44 * @{ 45 */ 46 47 typedef uint32_t AVCRC; 48 49 typedef enum { 50 AV_CRC_8_ATM, 51 AV_CRC_16_ANSI, 52 AV_CRC_16_CCITT, 53 AV_CRC_32_IEEE, 54 AV_CRC_32_IEEE_LE, /*< reversed bitorder version of AV_CRC_32_IEEE */ 55 AV_CRC_16_ANSI_LE, /*< reversed bitorder version of AV_CRC_16_ANSI */ 56 AV_CRC_24_IEEE, 57 AV_CRC_8_EBU, 58 AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */ 59 }AVCRCId; 60 61 /** 62 * Initialize a CRC table. 63 * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 64 * @param le If 1, the lowest bit represents the coefficient for the highest 65 * exponent of the corresponding polynomial (both for poly and 66 * actual CRC). 67 * If 0, you must swap the CRC parameter and the result of av_crc 68 * if you need the standard representation (can be simplified in 69 * most cases to e.g. bswap16): 70 * av_bswap32(crc << (32-bits)) 71 * @param bits number of bits for the CRC 72 * @param poly generator polynomial without the x**bits coefficient, in the 73 * representation as specified by le 74 * @param ctx_size size of ctx in bytes 75 * @return <0 on failure 76 */ 77 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size); 78 79 /** 80 * Get an initialized standard CRC table. 81 * @param crc_id ID of a standard CRC 82 * @return a pointer to the CRC table or NULL on failure 83 */ 84 const AVCRC *av_crc_get_table(AVCRCId crc_id); 85 86 /** 87 * Calculate the CRC of a block. 88 * @param crc CRC of previous blocks if any or initial value for CRC 89 * @return CRC updated with the data from the given block 90 * 91 * @see av_crc_init() "le" parameter 92 */ 93 uint32_t av_crc(const AVCRC *ctx, uint32_t crc, 94 const uint8_t *buffer, size_t length) av_pure; 95 96 /** 97 * @} 98 */ 99 100 #endif /* AVUTIL_CRC_H */ 101