Subversion Repositories planix.SVN

Rev

Rev 2 | Details | Compare with Previous | Last modification | View Log | RSS feed

Rev Author Line No. Line
2 - 1 
#include <u.h>
2 
#include <libc.h>
3 
#include <flate.h>
4 
 
5 
ulong*
6 
mkcrctab(ulong poly)
7 
{
8 
	ulong *crctab;
9 
	ulong crc;
10 
	int i, j;
11 
 
12 
	crctab = malloc(256 * sizeof(ulong));
13 
	if(crctab == nil)
14 
		return nil;
15 
 
16 
	for(i = 0; i < 256; i++){
17 
		crc = i;
18 
		for(j = 0; j < 8; j++){
19 
			if(crc & 1)
20 
				crc = (crc >> 1) ^ poly;
21 
			else
22 
				crc >>= 1;
23 
		}
24 
		crctab[i] = crc;
25 
	}
26 
	return crctab;
27 
}
28 
 
29 
ulong
30 
blockcrc(ulong *crctab, ulong crc, void *vbuf, int n)
31 
{
32 
	uchar *buf, *ebuf;
33 
 
34 
	crc ^= 0xffffffff;
35 
	buf = vbuf;
36 
	ebuf = buf + n;
37 
	while(buf < ebuf)
38 
		crc = crctab[(crc & 0xff) ^ *buf++] ^ (crc >> 8);
39 
	return crc ^ 0xffffffff;
40 
}