[1064] in Coldmud discussion meeting

Re: [COLD] Standard way of converting "a.b.c.d" to 'struct in_addr'

daemon@ATHENA.MIT.EDU (Tue Aug 13 11:18:51 1996 )

Date: Tue, 13 Aug 1996 16:44:46 +0100
From: Luc Girardin <girardin@hei.unige.ch>
To: Brandon Gillespie <brandon@tombstone.sunrem.com>
Cc: coldstuff@cold.org
Reply-to: girardin@hei.unige.ch

Brandon Gillespie wrote:

> Right now the driver uses inet_ntoa(), which I _thought_ was standard
> (all of the systems' man pages I checked had it, and preferred it over
> other functions).  However, Solaris does not have it.  I've been idly
> working on an alternative, but I do not have enough reference to come up
> with a solution.  I primarily need more details on what exactly
> inet_makeaddr() expects, and how to get "a.b.c.d" to the form it expects..

Try the following code, it should do the job and work on every
platform...

int inet_aton (const char *cp, struct in_addr *addr)
{
  unsigned long parts[4];
  register unsigned long val;
  register unsigned long part0;
  register unsigned long part1;
  register unsigned long part2;
  register unsigned long part3;
  int part;
  char *next;

  part = 0;

  for (;;)
    {
      if (!isdigit (*cp)) /* not decimal digit or leading 0, 0x */
	return 0;

      errno = 0;
      parts[part++] = strtoul (cp, &next, 0); /* leading 0=octal, 0x=hex
*/
      if (errno == ERANGE)
	return 0;
      
      if (*next == '.')
	{
	  if (part >= 4)
	    return 0;

	  cp = next + 1;
	}
      else
	break; /* from for loop */
    }
  /* Check for trailing non-whitespace characters */

  if (strlen (next) != strspn (next, " \t\n\v\f\r"))
    return 0;

  /* Concoct the address according to the number of parts specified. */

  val = 0;
  part0 = parts[0];
  part1 = parts[1];
  part2 = parts[2];
  part3 = parts[3];

  switch (part)
    {
    case 4: /* a.b.c.d -- 8.8.8.8 bits */
      if (part3 > 0xff || part2 > 0xff)
	return 0;
      val = part3;
      part2 <<= 8;
      /* FALLTHROUGH */
    case 3: /* a.b.c -- 8.8.16 bits */
      if (part2 > 0xffff || part1 > 0xff)
	return 0;
      val |= part2;
      part1 <<= 16;
      /* FALLTHROUGH */
    case 2: /* a.b -- 8.24 bits */
      if (part1 > 0xffffff || part0 > 0xff)
	return 0;
      val |= part1;
      part0 <<= 24;
      /* FALLTHROUGH */
    case 1: /* a -- 32 bits */
      val |= part0;
    }

  addr->s_addr = htonl (val);
  return 1;
}
 
Cheers

-----BEGIN PBP PUBLIC INFO BLOCK-----
Luc Girardin    The   Graduate   Institute  of  International   Studies
                Institut Universitaire de Hautes Etudes Internationales
                Geneva,  Switzerland,  http://heiwww.unige.ch/girardin/

                        "Sane sicut lux seipsam et tenebras manifestat,
                                  sic veritas normal sui et falsi est."
                                 Spinoza, Ethics, Pt II, Prop. 43, 1675
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