2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
4 * This file is part of FFmpeg.
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.
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.
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
24 * Public header for CRC hash function implementation.
32 #include "attributes.h"
36 * @defgroup lavu_crc32 CRC
38 * CRC (Cyclic Redundancy Check) hash function implementation.
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
47 typedef uint32_t AVCRC;
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 #if FF_API_CRC_BIG_TABLE
60 #endif /* FF_API_CRC_BIG_TABLE */
61 AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */
65 * Initialize a CRC table.
66 * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
67 * @param le If 1, the lowest bit represents the coefficient for the highest
68 * exponent of the corresponding polynomial (both for poly and
70 * If 0, you must swap the CRC parameter and the result of av_crc
71 * if you need the standard representation (can be simplified in
72 * most cases to e.g. bswap16):
73 * av_bswap32(crc << (32-bits))
74 * @param bits number of bits for the CRC
75 * @param poly generator polynomial without the x**bits coefficient, in the
76 * representation as specified by le
77 * @param ctx_size size of ctx in bytes
78 * @return <0 on failure
80 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
83 * Get an initialized standard CRC table.
84 * @param crc_id ID of a standard CRC
85 * @return a pointer to the CRC table or NULL on failure
87 const AVCRC *av_crc_get_table(AVCRCId crc_id);
90 * Calculate the CRC of a block.
91 * @param crc CRC of previous blocks if any or initial value for CRC
92 * @return CRC updated with the data from the given block
94 * @see av_crc_init() "le" parameter
96 uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
97 const uint8_t *buffer, size_t length) av_pure;
103 #endif /* AVUTIL_CRC_H */