crc.h (3259B)
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 34 /** 35 * @defgroup lavu_crc32 CRC 36 * @ingroup lavu_hash 37 * CRC (Cyclic Redundancy Check) hash function implementation. 38 * 39 * This module supports numerous CRC polynomials, in addition to the most 40 * widely used CRC-32-IEEE. See @ref AVCRCId for a list of available 41 * polynomials. 42 * 43 * @{ 44 */ 45 46 typedef uint32_t AVCRC; 47 48 typedef enum { 49 AV_CRC_8_ATM, 50 AV_CRC_16_ANSI, 51 AV_CRC_16_CCITT, 52 AV_CRC_32_IEEE, 53 AV_CRC_32_IEEE_LE, /*< reversed bitorder version of AV_CRC_32_IEEE */ 54 AV_CRC_16_ANSI_LE, /*< reversed bitorder version of AV_CRC_16_ANSI */ 55 AV_CRC_24_IEEE, 56 AV_CRC_8_EBU, 57 AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */ 58 }AVCRCId; 59 60 /** 61 * Initialize a CRC table. 62 * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 63 * @param le If 1, the lowest bit represents the coefficient for the highest 64 * exponent of the corresponding polynomial (both for poly and 65 * actual CRC). 66 * If 0, you must swap the CRC parameter and the result of av_crc 67 * if you need the standard representation (can be simplified in 68 * most cases to e.g. bswap16): 69 * av_bswap32(crc << (32-bits)) 70 * @param bits number of bits for the CRC 71 * @param poly generator polynomial without the x**bits coefficient, in the 72 * representation as specified by le 73 * @param ctx_size size of ctx in bytes 74 * @return <0 on failure 75 */ 76 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size); 77 78 /** 79 * Get an initialized standard CRC table. 80 * @param crc_id ID of a standard CRC 81 * @return a pointer to the CRC table or NULL on failure 82 */ 83 const AVCRC *av_crc_get_table(AVCRCId crc_id); 84 85 /** 86 * Calculate the CRC of a block. 87 * @param ctx initialized AVCRC array (see av_crc_init()) 88 * @param crc CRC of previous blocks if any or initial value for CRC 89 * @param buffer buffer whose CRC to calculate 90 * @param length length of the buffer 91 * @return CRC updated with the data from the given block 92 * 93 * @see av_crc_init() "le" parameter 94 */ 95 uint32_t av_crc(const AVCRC *ctx, uint32_t crc, 96 const uint8_t *buffer, size_t length) av_pure; 97 98 /** 99 * @} 100 */ 101 102 #endif /* AVUTIL_CRC_H */