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 #include <afs/stds.h>
  39
  40 #include <roken.h>
  41
  42 #include <rx/xdr.h>
  43 #include <rx/rx.h>
  44 #include "rxkad.h"
  45 #include "lifetimes.h"
  46
  47 static u_long table[256];
  48
  49 #define CRC_GEN 0xEDB88320L
  50
  51 void
  52 _rxkad_crc_init_table(void)
  53 {
  54     static int flag = 0;
  55     unsigned long crc, poly;
  56     int i, j;
  57
  58     if (flag)
  59         return;
  60     poly = CRC_GEN;
  61     for (i = 0; i < 256; i++) {
  62         crc = i;
  63         for (j = 8; j > 0; j--) {
  64             if (crc & 1) {
  65                 crc = (crc >> 1) ^ poly;
  66             } else {
  67                 crc >>= 1;
  68             }
  69         }
  70         table[i] = crc;
  71     }
  72     flag = 1;
  73 }
  74
  75 afs_uint32
  76 _rxkad_crc_update(const char *p, size_t len, afs_uint32 res)
  77 {
  78     while (len--)
  79         res = table[(res ^ *p++) & 0xFF] ^ (res >> 8);
  80     return res & 0xFFFFFFFF;
  81 }