wsutil/adler32.c

   1 /* adler32.c
   2  * Compute the Adler32 checksum (RFC 1950)
   3  * 2003 Tomas Kukosa
   4  * Based on code from RFC 1950 (Chapter 9. Appendix: Sample code)
   5  *
   6  * $Id$
   7  *
   8  * Wireshark - Network traffic analyzer
   9  * By Gerald Combs <gerald@wireshark.org>
  10  * Copyright 1998 Gerald Combs
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  25  */
  26
  27 #include <string.h>
  28
  29 #include <glib.h>
  30
  31 #include <wsutil/adler32.h>
  32
  33 #define BASE 65521 /* largest prime smaller than 65536 */
  34
  35 /*--- update_adler32 --------------------------------------------------------*/
  36 guint32 update_adler32(guint32 adler, const guint8 *buf, size_t len)
  37 {
  38   guint32 s1 = adler & 0xffff;
  39   guint32 s2 = (adler >> 16) & 0xffff;
  40   size_t n;
  41
  42   for (n = 0; n < len; n++) {
  43     s1 = (s1 + buf[n]) % BASE;
  44     s2 = (s2 + s1)     % BASE;
  45   }
  46   return (s2 << 16) + s1;
  47 }
  48
  49 /*--- adler32 ---------------------------------------------------------------*/
  50 guint32 adler32_bytes(const guint8 *buf, size_t len)
  51 {
  52   return update_adler32(1, buf, len);
  53 }
  54
  55 /*--- adler32_str -----------------------------------------------------------*/
  56 guint32 adler32_str(const char *buf)
  57 {
  58   return update_adler32(1, (const guint8*)buf, strlen(buf));
  59 }
  60
  61 /*---------------------------------------------------------------------------*/