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  * Wireshark - Network traffic analyzer
   7  * By Gerald Combs <gerald@wireshark.org>
   8  * Copyright 1998 Gerald Combs
   9  *
  10  * SPDX-License-Identifier: GPL-2.0-or-later
  11  */
  12
  13 #include <wsutil/adler32.h>
  14
  15 #ifdef HAVE_ZLIBNG
  16 #include <zlib-ng.h>
  17 #else
  18 #ifdef HAVE_ZLIB
  19 #include <zlib.h>
  20 #endif /* HAVE_ZLIB */
  21 #endif
  22 #include <string.h>
  23
  24 #define BASE 65521 /* largest prime smaller than 65536 */
  25
  26 /*--- update_adler32 --------------------------------------------------------*/
  27 uint32_t update_adler32(uint32_t adler, const uint8_t *buf, size_t len)
  28 {
  29 #if defined (HAVE_ZLIB) || defined (HAVE_ZLIBNG)
  30 #ifdef HAVE_ZLIBNG
  31   return (uint32_t)zng_adler32(adler, buf, len);
  32 #else
  33   return (uint32_t)adler32(adler, buf, len);
  34 #endif
  35 #endif
  36   uint32_t s1 = adler & 0xffff;
  37   uint32_t s2 = (adler >> 16) & 0xffff;
  38   size_t n;
  39
  40   for (n = 0; n < len; n++) {
  41     s1 = (s1 + buf[n]) % BASE;
  42     s2 = (s2 + s1)     % BASE;
  43   }
  44   return (s2 << 16) + s1;
  45
  46 }
  47
  48 /*--- adler32 ---------------------------------------------------------------*/
  49 uint32_t adler32_bytes(const uint8_t *buf, size_t len)
  50 {
  51   return update_adler32(1, buf, len);
  52 }
  53
  54 /*--- adler32_str -----------------------------------------------------------*/
  55 uint32_t adler32_str(const char *buf)
  56 {
  57   return update_adler32(1, (const uint8_t*)buf, strlen(buf));
  58 }
  59
  60 /*---------------------------------------------------------------------------*/
  61
  62 /*
  63  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
  64  *
  65  * Local Variables:
  66  * c-basic-offset: 2
  67  * tab-width: 8
  68  * indent-tabs-mode: nil
  69  * End:
  70  *
  71  * ex: set shiftwidth=2 tabstop=8 expandtab:
  72  * :indentSize=2:tabSize=8:noTabs=true:
  73  */