add support for downmixing to stereo or mono
[ffmpeg-lucabe.git] / libavutil / crc.c
blob02fb860b86f48b36e7cb67d5ae6c95dc9b76868b
1 /*
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
21 #include "common.h"
22 #include "crc.h"
24 #if LIBAVUTIL_VERSION_INT < (50<<16)
25 AVCRC *av_crcEDB88320;
26 AVCRC *av_crc04C11DB7;
27 AVCRC *av_crc8005 ;
28 AVCRC *av_crc07 ;
29 #else
30 AVCRC av_crcEDB88320[257];
31 AVCRC av_crc04C11DB7[257];
32 AVCRC av_crc8005 [257];
33 AVCRC av_crc07 [257];
34 #endif
36 /**
37 * Inits a crc table.
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){
43 int i, j;
44 uint32_t c;
46 if (bits < 8 || bits > 32 || poly >= (1LL<<bits))
47 return -1;
48 if (ctx_size != sizeof(AVCRC)*257 && ctx_size != sizeof(AVCRC)*1024)
49 return -1;
51 for (i = 0; i < 256; i++) {
52 if (le) {
53 for (c = i, j = 0; j < 8; j++)
54 c = (c>>1)^(poly & (-(c&1)));
55 ctx[i] = c;
56 } else {
57 for (c = i << 24, j = 0; j < 8; j++)
58 c = (c<<1) ^ ((poly<<(32-bits)) & (((int32_t)c)>>31) );
59 ctx[i] = bswap_32(c);
62 ctx[256]=1;
63 #ifndef CONFIG_SMALL
64 if(ctx_size >= sizeof(AVCRC)*1024)
65 for (i = 0; i < 256; i++)
66 for(j=0; j<3; j++)
67 ctx[256*(j+1) + i]= (ctx[256*j + i]>>8) ^ ctx[ ctx[256*j + i]&0xFF ];
68 #endif
70 return 0;
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;
76 #ifndef CONFIG_SMALL
77 if(!ctx[256])
78 while(buffer<end-3){
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) )];
85 #endif
86 while(buffer<end)
87 crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8);
89 return crc;
92 #ifdef TEST
93 #undef printf
94 main(){
95 uint8_t buf[1999];
96 int i;
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++)
104 buf[i]= i+i*i;
106 for(i=0; i<4; 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)));
111 #endif