blob: 8085c23e8189ef82d9bc90b2d7f51845f2798422 [file] [log] [blame]
#include <u.h>
#include <libc.h>
#include <flate.h>
uint32*
mkcrctab(uint32 poly)
{
uint32 *crctab;
uint32 crc;
int i, j;
crctab = malloc(256 * sizeof(ulong));
if(crctab == nil)
return nil;
for(i = 0; i < 256; i++){
crc = i;
for(j = 0; j < 8; j++){
if(crc & 1)
crc = (crc >> 1) ^ poly;
else
crc >>= 1;
}
crctab[i] = crc;
}
return crctab;
}
uint32
blockcrc(uint32 *crctab, uint32 crc, void *vbuf, int n)
{
uchar *buf, *ebuf;
crc ^= 0xffffffff;
buf = vbuf;
ebuf = buf + n;
while(buf < ebuf)
crc = crctab[(crc & 0xff) ^ *buf++] ^ (crc >> 8);
return crc ^ 0xffffffff;
}