/* 
 * setguid.c - receive a GUID from GUID.org and set a site-specific cookie
 *
 * Usually used as a reponse to the GUID.org getguid routine, i.e.:
 * <img width=1 height=1 src="http://www.guid.org/getguid?Redirect=http:%2F%2Fwww.mysite.com/setguid.cgi">
 *
 * For more information, see http://www.guid.org/usage.html
 *
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define GUIDLEN 32
char guidstr[] = "GUID=";
char gifbits[] = "GIF89a\x01\x00\x01\x00\x80\xFF\x00\xC0\xC0\xC0\x00\x00\x00!\xF9\x04\x01\x00\x00\x00\x00,\x00\x00\x00\x00\x01\x00\x01\x00@\x02\x02D\x01\x00;";

int main() {
  char *query, *begin, *end, guid[GUIDLEN+1];
  int i;

  guid[0] = 0;
  query = getenv("QUERY_STRING");
  if (query && query[0] && (begin = strstr(query, guidstr))) {
    begin += sizeof(guidstr)-1;
    for (end = begin; *end && (*end != '&'); end++) ;
    if (end-begin > GUIDLEN) /* truncate overly long GUIDs */
      end = begin+GUIDLEN;
    strncpy(guid, begin, end-begin+1);
    guid[GUIDLEN] = 0;
  }
  if (guid[0])
    printf("Set-Cookie: GUID=%s; Expires=Thu 31-Dec-37 23:59:59 GMT; Path=/\n", guid);
  printf("Content-Type: image/gif\n\n");
  for (i=0; i<sizeof(gifbits)-1; i++)
    putchar(gifbits[i]);
}