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      1 /*	$NetBSD: crc.c,v 1.2 2017/01/28 21:31:49 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1997 - 2000 Kungliga Tekniska Hgskolan
      5  * (Royal Institute of Technology, Stockholm, Sweden).
      6  * All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  *
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  *
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * 3. Neither the name of the Institute nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #include "krb5_locl.h"
     37 
     38 static u_long table[256];
     39 
     40 #define CRC_GEN 0xEDB88320L
     41 
     42 KRB5_LIB_FUNCTION void KRB5_LIB_CALL
     43 _krb5_crc_init_table(void)
     44 {
     45     static int flag = 0;
     46     unsigned long crc, poly;
     47     unsigned int i, j;
     48 
     49     if(flag) return;
     50     poly = CRC_GEN;
     51     for (i = 0; i < 256; i++) {
     52 	crc = i;
     53 	for (j = 8; j > 0; j--) {
     54 	    if (crc & 1) {
     55 		crc = (crc >> 1) ^ poly;
     56 	    } else {
     57 		crc >>= 1;
     58 	    }
     59 	}
     60 	table[i] = crc;
     61     }
     62     flag = 1;
     63 }
     64 
     65 KRB5_LIB_FUNCTION uint32_t KRB5_LIB_CALL
     66 _krb5_crc_update (const char *p, size_t len, uint32_t res)
     67 {
     68     while (len--)
     69 	res = table[(res ^ *p++) & 0xFF] ^ (res >> 8);
     70     return res & 0xFFFFFFFF;
     71 }
     72