FFmpeg 4.2.2
crc.h
Go to the documentation of this file.
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#include "version.h"
34
35/**
36 * @defgroup lavu_crc32 CRC
37 * @ingroup lavu_hash
38 * CRC (Cyclic Redundancy Check) hash function implementation.
39 *
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
42 * polynomials.
43 *
44 * @{
45 */
46
47typedef uint32_t AVCRC;
48
49typedef enum {
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 */
58 AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */
59}AVCRCId;
60
61/**
62 * Initialize a CRC table.
63 * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
64 * @param le If 1, the lowest bit represents the coefficient for the highest
65 * exponent of the corresponding polynomial (both for poly and
66 * actual CRC).
67 * If 0, you must swap the CRC parameter and the result of av_crc
68 * if you need the standard representation (can be simplified in
69 * most cases to e.g. bswap16):
70 * av_bswap32(crc << (32-bits))
71 * @param bits number of bits for the CRC
72 * @param poly generator polynomial without the x**bits coefficient, in the
73 * representation as specified by le
74 * @param ctx_size size of ctx in bytes
75 * @return <0 on failure
76 */
77int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
78
79/**
80 * Get an initialized standard CRC table.
81 * @param crc_id ID of a standard CRC
82 * @return a pointer to the CRC table or NULL on failure
83 */
85
86/**
87 * Calculate the CRC of a block.
88 * @param crc CRC of previous blocks if any or initial value for CRC
89 * @return CRC updated with the data from the given block
90 *
91 * @see av_crc_init() "le" parameter
92 */
93uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
94 const uint8_t *buffer, size_t length) av_pure;
95
96/**
97 * @}
98 */
99
100#endif /* AVUTIL_CRC_H */
Macro definitions for various function/variable attributes.
#define av_pure
Definition: attributes.h:70
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:49
uint32_t AVCRC
Definition: crc.h:47
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:52
@ AV_CRC_32_IEEE
Definition: crc.h:53
@ AV_CRC_24_IEEE
Definition: crc.h:56
@ AV_CRC_8_EBU
Definition: crc.h:57
@ AV_CRC_8_ATM
Definition: crc.h:50
@ AV_CRC_32_IEEE_LE
Definition: crc.h:54
@ AV_CRC_MAX
Definition: crc.h:58
@ AV_CRC_16_ANSI
Definition: crc.h:51
@ AV_CRC_16_ANSI_LE
Definition: crc.h:55
swscale version macros