crc.c revision 233294 
1/*
2 * Copyright (c) 1997 - 2000 Kungliga Tekniska H��gskolan
3 * (Royal Institute of Technology, Stockholm, Sweden).
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * 3. Neither the name of the Institute nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include "krb5_locl.h"
35
36static u_long table[256];
37
38#define CRC_GEN 0xEDB88320L
39
40void
41_krb5_crc_init_table(void)
42{
43    static int flag = 0;
44    unsigned long crc, poly;
45    unsigned int i, j;
46
47    if(flag) return;
48    poly = CRC_GEN;
49    for (i = 0; i < 256; i++) {
50	crc = i;
51	for (j = 8; j > 0; j--) {
52	    if (crc & 1) {
53		crc = (crc >> 1) ^ poly;
54	    } else {
55		crc >>= 1;
56	    }
57	}
58	table[i] = crc;
59    }
60    flag = 1;
61}
62
63uint32_t
64_krb5_crc_update (const char *p, size_t len, uint32_t res)
65{
66    while (len--)
67	res = table[(res ^ *p++) & 0xFF] ^ (res >> 8);
68    return res & 0xFFFFFFFF;
69}
70