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"
35 * @defgroup lavu_crc32 CRC
37 * CRC (Cyclic Redundancy Check) hash function implementation.
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
46 typedef uint32_t AVCRC
;
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 */
57 AV_CRC_MAX
, /*< Not part of public API! Do not use outside libavutil. */
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
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
76 int av_crc_init(AVCRC
*ctx
, int le
, int bits
, uint32_t poly
, int ctx_size
);
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
83 const AVCRC
*av_crc_get_table(AVCRCId crc_id
);
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
93 * @see av_crc_init() "le" parameter
95 uint32_t av_crc(const AVCRC
*ctx
, uint32_t crc
,
96 const uint8_t *buffer
, size_t length
) av_pure
;
102 #endif /* AVUTIL_CRC_H */