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>
 4 b6afd33e 2003-11-23 devnull 
 5 9a054520 2010-02-08 rsc uint32*
 6 9a054520 2010-02-08 rsc mkcrctab(uint32 poly)
 7 b6afd33e 2003-11-23 devnull {
 8 9a054520 2010-02-08 rsc 	uint32 *crctab;
 9 9a054520 2010-02-08 rsc 	uint32 crc;
10 b6afd33e 2003-11-23 devnull 	int i, j;
11 b6afd33e 2003-11-23 devnull 
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;
15 b6afd33e 2003-11-23 devnull 
16 b6afd33e 2003-11-23 devnull 	for(i = 0; i < 256; i++){
17 b6afd33e 2003-11-23 devnull 		crc = 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;
21 b6afd33e 2003-11-23 devnull 			else
22 b6afd33e 2003-11-23 devnull 				crc >>= 1;
23 b6afd33e 2003-11-23 devnull 		}
24 b6afd33e 2003-11-23 devnull 		crctab[i] = crc;
25 b6afd33e 2003-11-23 devnull 	}
26 b6afd33e 2003-11-23 devnull 	return crctab;
27 b6afd33e 2003-11-23 devnull }
28 b6afd33e 2003-11-23 devnull 
29 9a054520 2010-02-08 rsc uint32
30 9a054520 2010-02-08 rsc blockcrc(uint32 *crctab, uint32 crc, void *vbuf, int n)
31 b6afd33e 2003-11-23 devnull {
32 b6afd33e 2003-11-23 devnull 	uchar *buf, *ebuf;
33 b6afd33e 2003-11-23 devnull 
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;
40 b6afd33e 2003-11-23 devnull }