FFmpeg 5.1.4
crc.h
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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
46typedef uint32_t AVCRC;
47
48typedef enum {
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. */
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 */
76int 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 */
84
85/**
86 * Calculate the CRC of a block.
87 * @param crc CRC of previous blocks if any or initial value for CRC
88 * @return CRC updated with the data from the given block
89 *
90 * @see av_crc_init() "le" parameter
91 */
92uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
93 const uint8_t *buffer, size_t length) av_pure;
94
95/**
96 * @}
97 */
98
99#endif /* AVUTIL_CRC_H */
Macro definitions for various function/variable attributes.
#define av_pure
Definition: attributes.h:76
int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size)
Initialize a CRC table.
const AVCRC * av_crc_get_table(AVCRCId crc_id)
Get an initialized standard CRC table.
AVCRCId
Definition: crc.h:48
uint32_t AVCRC
Definition: crc.h:46
uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length) av_pure
Calculate the CRC of a block.
@ AV_CRC_16_CCITT
Definition: crc.h:51
@ AV_CRC_32_IEEE
Definition: crc.h:52
@ AV_CRC_24_IEEE
Definition: crc.h:55
@ AV_CRC_8_EBU
Definition: crc.h:56
@ AV_CRC_8_ATM
Definition: crc.h:49
@ AV_CRC_32_IEEE_LE
Definition: crc.h:53
@ AV_CRC_MAX
Definition: crc.h:57
@ AV_CRC_16_ANSI
Definition: crc.h:50
@ AV_CRC_16_ANSI_LE
Definition: crc.h:54