2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
4 * This file is part of FFmpeg.
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.
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.
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
24 #if LIBAVUTIL_VERSION_INT < (50<<16)
25 AVCRC
*av_crcEDB88320
;
26 AVCRC
*av_crc04C11DB7
;
30 AVCRC av_crcEDB88320
[257];
31 AVCRC av_crc04C11DB7
[257];
32 AVCRC av_crc8005
[257];
38 * @param ctx must be an array of sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
39 * @param cts_size size of ctx in bytes
40 * @return <0 on failure
42 int av_crc_init(AVCRC
*ctx
, int le
, int bits
, uint32_t poly
, int ctx_size
){
46 if (bits
< 8 || bits
> 32 || poly
>= (1LL<<bits
))
48 if (ctx_size
!= sizeof(AVCRC
)*257 && ctx_size
!= sizeof(AVCRC
)*1024)
51 for (i
= 0; i
< 256; i
++) {
53 for (c
= i
, j
= 0; j
< 8; j
++)
54 c
= (c
>>1)^(poly
& (-(c
&1)));
57 for (c
= i
<< 24, j
= 0; j
< 8; j
++)
58 c
= (c
<<1) ^ ((poly
<<(32-bits
)) & (((int32_t)c
)>>31) );
64 if(ctx_size
>= sizeof(AVCRC
)*1024)
65 for (i
= 0; i
< 256; i
++)
67 ctx
[256*(j
+1) + i
]= (ctx
[256*j
+ i
]>>8) ^ ctx
[ ctx
[256*j
+ i
]&0xFF ];
73 uint32_t av_crc(const AVCRC
*ctx
, uint32_t crc
, const uint8_t *buffer
, size_t length
){
74 const uint8_t *end
= buffer
+length
;
79 crc
^= le2me_32(*(uint32_t*)buffer
); buffer
+=4;
80 crc
= ctx
[3*256 + ( crc
&0xFF)]
81 ^ctx
[2*256 + ((crc
>>8 )&0xFF)]
82 ^ctx
[1*256 + ((crc
>>16)&0xFF)]
83 ^ctx
[0*256 + ((crc
>>24) )];
87 crc
= ctx
[((uint8_t)crc
) ^ *buffer
++] ^ (crc
>> 8);
97 int p
[4][4]={{1, 32, 0xedb88320L
, 0x3D5CDD04},
98 {0, 32, 0x04c11db7L
, 0xC0F5BAE0},
99 {0, 16, 0x8005 , 0x1FBB },
100 {0, 8, 0x07 , 0xE3 },};
101 AVCRC ctx
[1 ? 1024:257];
103 for(i
=0; i
<sizeof(buf
); i
++)
107 av_crc_init(ctx
, p
[i
][0], p
[i
][1], p
[i
][2], sizeof(ctx
));
108 printf("crc %08X =%X\n", p
[i
][2], av_crc(ctx
, 0, buf
, sizeof(buf
)));