crc.h (2595B)
1 /* 2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at> 3 * 4 * This file is part of Libav. 5 * 6 * Libav 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 * Libav 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 Libav; if not, write to the Free Software 18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 19 */ 20 21 #ifndef AVUTIL_CRC_H 22 #define AVUTIL_CRC_H 23 24 #include <stdint.h> 25 #include <stddef.h> 26 #include "attributes.h" 27 28 typedef uint32_t AVCRC; 29 30 typedef enum { 31 AV_CRC_8_ATM, 32 AV_CRC_16_ANSI, 33 AV_CRC_16_CCITT, 34 AV_CRC_32_IEEE, 35 AV_CRC_32_IEEE_LE, /*< reversed bitorder version of AV_CRC_32_IEEE */ 36 AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */ 37 }AVCRCId; 38 39 /** 40 * Initialize a CRC table. 41 * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 42 * @param le If 1, the lowest bit represents the coefficient for the highest 43 * exponent of the corresponding polynomial (both for poly and 44 * actual CRC). 45 * If 0, you must swap the CRC parameter and the result of av_crc 46 * if you need the standard representation (can be simplified in 47 * most cases to e.g. bswap16): 48 * av_bswap32(crc << (32-bits)) 49 * @param bits number of bits for the CRC 50 * @param poly generator polynomial without the x**bits coefficient, in the 51 * representation as specified by le 52 * @param ctx_size size of ctx in bytes 53 * @return <0 on failure 54 */ 55 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size); 56 57 /** 58 * Get an initialized standard CRC table. 59 * @param crc_id ID of a standard CRC 60 * @return a pointer to the CRC table or NULL on failure 61 */ 62 const AVCRC *av_crc_get_table(AVCRCId crc_id); 63 64 /** 65 * Calculate the CRC of a block. 66 * @param crc CRC of previous blocks if any or initial value for CRC 67 * @return CRC updated with the data from the given block 68 * 69 * @see av_crc_init() "le" parameter 70 */ 71 uint32_t av_crc(const AVCRC *ctx, uint32_t crc, 72 const uint8_t *buffer, size_t length) av_pure; 73 74 #endif /* AVUTIL_CRC_H */