1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
|
/*
* copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#include "common.h"
#include "bswap.h"
#include "crc.h"
#if CONFIG_HARDCODED_TABLES
#include "crc_data.h"
#else
static struct {
uint8_t le;
uint8_t bits;
uint32_t poly;
} av_crc_table_params[AV_CRC_MAX] = {
[AV_CRC_8_ATM] = { 0, 8, 0x07 },
[AV_CRC_16_ANSI] = { 0, 16, 0x8005 },
[AV_CRC_16_CCITT] = { 0, 16, 0x1021 },
[AV_CRC_32_IEEE] = { 0, 32, 0x04C11DB7 },
[AV_CRC_32_IEEE_LE] = { 1, 32, 0xEDB88320 },
};
static AVCRC av_crc_table[AV_CRC_MAX][257];
#endif
/**
* Initialize a CRC table.
* @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
* @param le If 1, the lowest bit represents the coefficient for the highest
* exponent of the corresponding polynomial (both for poly and
* actual CRC).
* If 0, you must swap the CRC parameter and the result of av_crc
* if you need the standard representation (can be simplified in
* most cases to e.g. bswap16):
* av_bswap32(crc << (32-bits))
* @param bits number of bits for the CRC
* @param poly generator polynomial without the x**bits coefficient, in the
* representation as specified by le
* @param ctx_size size of ctx in bytes
* @return <0 on failure
*/
int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){
unsigned i, j;
uint32_t c;
if (bits < 8 || bits > 32 || poly >= (1LL<<bits))
return -1;
if (ctx_size != sizeof(AVCRC)*257 && ctx_size != sizeof(AVCRC)*1024)
return -1;
for (i = 0; i < 256; i++) {
if (le) {
for (c = i, j = 0; j < 8; j++)
c = (c>>1)^(poly & (-(c&1)));
ctx[i] = c;
} else {
for (c = i << 24, j = 0; j < 8; j++)
c = (c<<1) ^ ((poly<<(32-bits)) & (((int32_t)c)>>31) );
ctx[i] = av_bswap32(c);
}
}
ctx[256]=1;
#if !CONFIG_SMALL
if(ctx_size >= sizeof(AVCRC)*1024)
for (i = 0; i < 256; i++)
for(j=0; j<3; j++)
ctx[256*(j+1) + i]= (ctx[256*j + i]>>8) ^ ctx[ ctx[256*j + i]&0xFF ];
#endif
return 0;
}
/**
* Get an initialized standard CRC table.
* @param crc_id ID of a standard CRC
* @return a pointer to the CRC table or NULL on failure
*/
const AVCRC *av_crc_get_table(AVCRCId crc_id){
#if !CONFIG_HARDCODED_TABLES
if (!av_crc_table[crc_id][FF_ARRAY_ELEMS(av_crc_table[crc_id])-1])
if (av_crc_init(av_crc_table[crc_id],
av_crc_table_params[crc_id].le,
av_crc_table_params[crc_id].bits,
av_crc_table_params[crc_id].poly,
sizeof(av_crc_table[crc_id])) < 0)
return NULL;
#endif
return av_crc_table[crc_id];
}
/**
* Calculate the CRC of a block.
* @param crc CRC of previous blocks if any or initial value for CRC
* @return CRC updated with the data from the given block
*
* @see av_crc_init() "le" parameter
*/
uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length){
const uint8_t *end= buffer+length;
#if !CONFIG_SMALL
if(!ctx[256]) {
while(((intptr_t) buffer & 3) && buffer < end)
crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8);
while(buffer<end-3){
crc ^= av_le2ne32(*(const uint32_t*)buffer); buffer+=4;
crc = ctx[3*256 + ( crc &0xFF)]
^ctx[2*256 + ((crc>>8 )&0xFF)]
^ctx[1*256 + ((crc>>16)&0xFF)]
^ctx[0*256 + ((crc>>24) )];
}
}
#endif
while(buffer<end)
crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8);
return crc;
}
#ifdef TEST
#undef printf
int main(void){
uint8_t buf[1999];
int i;
int p[4][3]={{AV_CRC_32_IEEE_LE, 0xEDB88320, 0x3D5CDD04},
{AV_CRC_32_IEEE , 0x04C11DB7, 0xC0F5BAE0},
{AV_CRC_16_ANSI , 0x8005, 0x1FBB },
{AV_CRC_8_ATM , 0x07, 0xE3 },};
const AVCRC *ctx;
for(i=0; i<sizeof(buf); i++)
buf[i]= i+i*i;
for(i=0; i<4; i++){
ctx = av_crc_get_table(p[i][0]);
printf("crc %08X =%X\n", p[i][1], av_crc(ctx, 0, buf, sizeof(buf)));
}
return 0;
}
#endif
|
