/* strtok.c
 * 
 * Get next token from string s (NULL on 2nd, 3rd, etc. calls),
 * where tokens are nonempty strings separated by runs of
 * chars from delim.  Writes NULs into s to end tokens.  delim need not
 * remain constant from call to call.
 */

#define  NULL      0

static char *scanpoint = NULL;

char *                                 /* NULL if no token left */
strtok(s, delim)
char *s;
register CONST char *delim;
{
         register char *scan;
         char *tok;
         register CONST char *dscan;

         if (s == NULL && scanpoint == NULL)
                   return(NULL);
         if (s != NULL)
                   scan = s;
         else
                   scan = scanpoint;

         /*
          * Scan leading delimiters.
          */
         for (; *scan != '\0'; scan++) {
                   for (dscan = delim; *dscan != '\0'; dscan++)
                             if (*scan == *dscan)
                                       break;
                   if (*dscan == '\0')
                             break;
         }
         if (*scan == '\0') {
                   scanpoint = NULL;
                   return(NULL);
         }

         tok = scan;

         /*
          * Scan token.
          */
         for (; *scan != '\0'; scan++) {
                   for (dscan = delim; *dscan != '\0';)    /* ++ moved down. */
                             if (*scan == *dscan++) {
                                       scanpoint = scan+1;
                                       *scan = '\0';
                                       return(tok);
                             }
         }

         /*
          * Reached end of string.
          */
         scanpoint = NULL;
         return(tok);
}