lib/krb5/crc.c

   1 /*
   2  * Copyright (c) 1997 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. All advertising materials mentioning features or use of this software
  18  *    must display the following acknowledgement:
  19  *      This product includes software developed by Kungliga Tekniska
  20  *      Högskolan and its contributors.
  21  *
  22  * 4. Neither the name of the Institute nor the names of its contributors
  23  *    may be used to endorse or promote products derived from this software
  24  *    without specific prior written permission.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  36  * SUCH DAMAGE.
  37  */
  38
  39 #include "krb5_locl.h"
  40
  41 RCSID("$Id$");
  42
  43 #include <stdio.h>
  44 #include "crc.h"
  45
  46 static u_long table[256];
  47
  48 #define CRC_GEN 0xEDB88320L
  49
  50 void
  51 crc_init_table(void)
  52 {
  53     static int flag = 0;
  54     unsigned long crc, poly;
  55     int     i, j;
  56
  57     if(flag) return;
  58     poly = CRC_GEN;
  59     for (i = 0; i < 256; i++) {
  60         crc = i;
  61         for (j = 8; j > 0; j--) {
  62             if (crc & 1) {
  63                 crc = (crc >> 1) ^ poly;
  64             } else {
  65                 crc >>= 1;
  66             }
  67         }
  68         table[i] = crc;
  69     }
  70     flag = 1;
  71 }
  72
  73 u_int32_t
  74 crc_update (char *p, size_t len, u_int32_t res)
  75 {
  76     while (len--)
  77         res = table[(res ^ *p++) & 0xFF] ^ (res >> 8);
  78     return res & 0xFFFFFFFF;
  79 }