FFmpeg
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 #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 */
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  */
77 int 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  */
84 const AVCRC *av_crc_get_table(AVCRCId crc_id);
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  */
93 uint32_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 */
AV_CRC_8_EBU
@ AV_CRC_8_EBU
Definition: crc.h:57
AVCRC
uint32_t AVCRC
Definition: crc.h:47
AV_CRC_24_IEEE
@ AV_CRC_24_IEEE
Definition: crc.h:56
av_pure
#define av_pure
Definition: attributes.h:78
AV_CRC_16_ANSI_LE
@ AV_CRC_16_ANSI_LE
Definition: crc.h:55
av_crc_init
int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size)
Initialize a CRC table.
Definition: crc.c:341
bits
uint8_t bits
Definition: vp3data.h:141
ctx
AVFormatContext * ctx
Definition: movenc.c:48
AV_CRC_16_ANSI
@ AV_CRC_16_ANSI
Definition: crc.h:51
av_crc_get_table
const AVCRC * av_crc_get_table(AVCRCId crc_id)
Get an initialized standard CRC table.
Definition: crc.c:374
attributes.h
AV_CRC_16_CCITT
@ AV_CRC_16_CCITT
Definition: crc.h:52
AV_CRC_32_IEEE
@ AV_CRC_32_IEEE
Definition: crc.h:53
version.h
buffer
the frame and frame reference mechanism is intended to as much as expensive copies of that data while still allowing the filters to produce correct results The data is stored in buffers represented by AVFrame structures Several references can point to the same frame buffer
Definition: filter_design.txt:49
av_crc
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:392
AV_CRC_MAX
@ AV_CRC_MAX
Definition: crc.h:58
AV_CRC_32_IEEE_LE
@ AV_CRC_32_IEEE_LE
Definition: crc.h:54
AV_CRC_8_ATM
@ AV_CRC_8_ATM
Definition: crc.h:50
AVCRCId
AVCRCId
Definition: crc.h:49