ffmpeg.libavutil.crc source code

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 module ffmpeg.libavutil.crc;
27 extern (C) @nogc nothrow:
28 
29 /**
30  * @defgroup lavu_crc32 CRC
31  * @ingroup lavu_hash
32  * CRC (Cyclic Redundancy Check) hash function implementation.
33  *
34  * This module supports numerous CRC polynomials, in addition to the most
35  * widely used CRC-32-IEEE. See @ref AVCRCId for a list of available
36  * polynomials.
37  *
38  * @{
39  */
40 
41 alias AVCRC = uint;
42 
43 enum AVCRCId
44 {
45     AV_CRC_8_ATM = 0,
46     AV_CRC_16_ANSI = 1,
47     AV_CRC_16_CCITT = 2,
48     AV_CRC_32_IEEE = 3,
49     AV_CRC_32_IEEE_LE = 4, /*< reversed bitorder version of AV_CRC_32_IEEE */
50     AV_CRC_16_ANSI_LE = 5, /*< reversed bitorder version of AV_CRC_16_ANSI */
51     AV_CRC_24_IEEE = 6,
52     AV_CRC_8_EBU = 7,
53     AV_CRC_MAX = 8 /*< Not part of public API! Do not use outside libavutil. */
54 }
55 
56 /**
57  * Initialize a CRC table.
58  * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
59  * @param le If 1, the lowest bit represents the coefficient for the highest
60  *           exponent of the corresponding polynomial (both for poly and
61  *           actual CRC).
62  *           If 0, you must swap the CRC parameter and the result of av_crc
63  *           if you need the standard representation (can be simplified in
64  *           most cases to e.g. bswap16):
65  *           av_bswap32(crc << (32-bits))
66  * @param bits number of bits for the CRC
67  * @param poly generator polynomial without the x**bits coefficient, in the
68  *             representation as specified by le
69  * @param ctx_size size of ctx in bytes
70  * @return <0 on failure
71  */
72 int av_crc_init (AVCRC* ctx, int le, int bits, uint poly, int ctx_size);
73 
74 /**
75  * Get an initialized standard CRC table.
76  * @param crc_id ID of a standard CRC
77  * @return a pointer to the CRC table or NULL on failure
78  */
79 const(AVCRC)* av_crc_get_table (AVCRCId crc_id);
80 
81 /**
82  * Calculate the CRC of a block.
83  * @param crc CRC of previous blocks if any or initial value for CRC
84  * @return CRC updated with the data from the given block
85  *
86  * @see av_crc_init() "le" parameter
87  */
88 uint av_crc (const(AVCRC)* ctx, uint crc, const(ubyte)* buffer, size_t length);
89 
90 /**
91  * @}
92  */
93 
94 /* AVUTIL_CRC_H */