1 b6afd33e 2003-11-23 devnull #include <u.h>
2 b6afd33e 2003-11-23 devnull #include <libc.h>
3 b6afd33e 2003-11-23 devnull #include <flate.h>
6 b6afd33e 2003-11-23 devnull mkcrctab(ulong poly)
8 b6afd33e 2003-11-23 devnull ulong *crctab;
9 b6afd33e 2003-11-23 devnull ulong crc;
10 b6afd33e 2003-11-23 devnull int i, j;
12 b6afd33e 2003-11-23 devnull crctab = malloc(256 * sizeof(ulong));
13 b6afd33e 2003-11-23 devnull if(crctab == nil)
14 b6afd33e 2003-11-23 devnull return nil;
16 b6afd33e 2003-11-23 devnull for(i = 0; i < 256; i++){
18 b6afd33e 2003-11-23 devnull for(j = 0; j < 8; j++){
19 b6afd33e 2003-11-23 devnull if(crc & 1)
20 b6afd33e 2003-11-23 devnull crc = (crc >> 1) ^ poly;
22 b6afd33e 2003-11-23 devnull crc >>= 1;
24 b6afd33e 2003-11-23 devnull crctab[i] = crc;
26 b6afd33e 2003-11-23 devnull return crctab;
30 b6afd33e 2003-11-23 devnull blockcrc(ulong *crctab, ulong crc, void *vbuf, int n)
32 b6afd33e 2003-11-23 devnull uchar *buf, *ebuf;
34 b6afd33e 2003-11-23 devnull crc ^= 0xffffffff;
35 b6afd33e 2003-11-23 devnull buf = vbuf;
36 b6afd33e 2003-11-23 devnull ebuf = buf + n;
37 b6afd33e 2003-11-23 devnull while(buf < ebuf)
38 b6afd33e 2003-11-23 devnull crc = crctab[(crc & 0xff) ^ *buf++] ^ (crc >> 8);
39 b6afd33e 2003-11-23 devnull return crc ^ 0xffffffff;