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#include "common.h"
#include "crc.h"
AVCRC *av_crcEDB88320;
AVCRC *av_crc04C11DB7;
AVCRC *av_crc8005 ;
AVCRC *av_crc07 ;
/**
* Inits a crc table.
* @param ctx must be an array of sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
* @param cts_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){
int 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] = bswap_32(c);
}
}
ctx[256]=1;
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 ];
return 0;
}
uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length){
const uint8_t *end= buffer+length;
if(!ctx[256])
while(buffer<end-3){
crc ^= le2me_32(*(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) )];
}
while(buffer<end)
crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8);
return crc;
}
#ifdef TEST
#undef printf
main(){
uint8_t buf[1999];
int i;
int p[4][4]={{1, 32, 0xedb88320L, 0x3D5CDD04},
{0, 32, 0x04c11db7L, 0xC0F5BAE0},
{0, 16, 0x8005 , 0x1FBB },
{0, 8, 0x07 , 0xE3 },};
AVCRC ctx[1 ? 1024:257];
for(i=0; i<sizeof(buf); i++)
buf[i]= i+i*i;
for(i=0; i<4; i++){
av_crc_init(ctx, p[i][0], p[i][1], p[i][2], sizeof(ctx));
printf("crc %08X =%X\n", p[i][2], av_crc(ctx, 0, buf, sizeof(buf)));
}
}
#endif
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