1  /*
 2   * Copyright (c) 1997 - 2000 Kungliga Tekniska Högskolan
 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  
36  static uint32_t table[256];
37  
38  #define CRC_GEN 0xEDB88320L
39  
40  void
41  _krb5_crc_init_table(void)
42  {
43      static int flag = 0;
44      uint32_t 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  
63  uint32_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  }