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comparison lib/libavutil/crc.h @ 2134:992d2e6f907d

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preparation for libavcodec
author zipi
date Tue, 31 Dec 2013 14:52:14 +0000
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2133:e378232bfd36 2134:992d2e6f907d
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 #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 */