| rsc | b6afd33 | 2003-11-23 18:19:18 +0000 | [diff] [blame] | 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 | } |
