/* adler32.c

 * Compute the Adler32 checksum (RFC 1950)

 * 2003 Tomas Kukosa

 * Based on code from RFC 1950 (Chapter 9. Appendix: Sample code)

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

#include <wsutil/adler32.h>

#ifdef HAVE_ZLIBNG

#include <zlib-ng.h>

#else

#ifdef HAVE_ZLIB

#include <zlib.h>

#endif /* HAVE_ZLIB */

#endif

#include <string.h>

#define BASE 65521 /* largest prime smaller than 65536 */

/*--- update_adler32 --------------------------------------------------------*/

uint32_t update_adler32(uint32_t adler, const uint8_t *buf, size_t len)

{

#if defined (HAVE_ZLIB) || defined (HAVE_ZLIBNG)

#ifdef HAVE_ZLIBNG

  return (uint32_t)zng_adler32(adler, buf, len);

#else

  return (uint32_t)adler32(adler, buf, len);

#endif

#endif

  uint32_t s1 = adler & 0xffff;

  uint32_t s2 = (adler >> 16) & 0xffff;

  size_t n;

  for (n = 0; n < len; n++) {

    s1 = (s1 + buf[n]) % BASE;

    s2 = (s2 + s1)     % BASE;

  }

  return (s2 << 16) + s1;

}

/*--- adler32 ---------------------------------------------------------------*/

uint32_t adler32_bytes(const uint8_t *buf, size_t len)

{

  return update_adler32(1, buf, len);

}

/*--- adler32_str -----------------------------------------------------------*/

uint32_t adler32_str(const char *buf)

{

  return update_adler32(1, (const uint8_t*)buf, strlen(buf));

}

/*---------------------------------------------------------------------------*/

/*

 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html

 *

 * Local Variables:

 * c-basic-offset: 2

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

 * ex: set shiftwidth=2 tabstop=8 expandtab:

 * :indentSize=2:tabSize=8:noTabs=true:

 */