FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
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 
47 typedef uint32_t AVCRC;
48 
49 typedef 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 */
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  */
76 int 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  */
83 const AVCRC *av_crc_get_table(AVCRCId crc_id);
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  */
92 uint32_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 */
#define av_pure
Definition: attributes.h:70
Macro definitions for various function/variable attributes.
uint8_t
int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size)
Initialize a CRC table.
Definition: crc.c:316
AVCRCId
Definition: crc.h:49
GLsizei GLsizei * length
Definition: opengl_enc.c:115
Libavutil version macros.
AVFormatContext * ctx
Definition: movenc.c:48
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.
Definition: crc.c:366
const AVCRC * av_crc_get_table(AVCRCId crc_id)
Get an initialized standard CRC table.
Definition: crc.c:349
Definition: crc.h:57
uint32_t AVCRC
Definition: crc.h:47
GLuint buffer
Definition: opengl_enc.c:102