src/rxkad/crc.c

   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 /* RCSID("$Heimdal: crc.c,v 1.9 2000/08/03 01:45:14 assar Exp $"); */
  35
  36 #include <afsconfig.h>
  37 #include <afs/param.h>
  38
  39
  40 #include <afs/stds.h>
  41 #include <sys/types.h>
  42 #ifdef AFS_NT40_ENV
  43 #include <winsock2.h>
  44 #else
  45 #include <netinet/in.h>
  46 #endif
  47 #include <string.h>
  48 #include <rx/xdr.h>
  49 #include <rx/rx.h>
  50 #include "rxkad.h"
  51 #include <des.h>
  52 #include "lifetimes.h"
  53
  54 static u_long table[256];
  55
  56 #define CRC_GEN 0xEDB88320L
  57
  58 void
  59 _rxkad_crc_init_table(void)
  60 {
  61     static int flag = 0;
  62     unsigned long crc, poly;
  63     int i, j;
  64
  65     if (flag)
  66         return;
  67     poly = CRC_GEN;
  68     for (i = 0; i < 256; i++) {
  69         crc = i;
  70         for (j = 8; j > 0; j--) {
  71             if (crc & 1) {
  72                 crc = (crc >> 1) ^ poly;
  73             } else {
  74                 crc >>= 1;
  75             }
  76         }
  77         table[i] = crc;
  78     }
  79     flag = 1;
  80 }
  81
  82 afs_uint32
  83 _rxkad_crc_update(const char *p, size_t len, afs_uint32 res)
  84 {
  85     while (len--)
  86         res = table[(res ^ *p++) & 0xFF] ^ (res >> 8);
  87     return res & 0xFFFFFFFF;
  88 }