source: buchla-68k/libsm/strtok.c@ 0580615

/*
   =============================================================================
        strtok.c -- tokenize a string
        Version 1 -- 1987-06-12

        Uses strpbrk and strspn to break 'string' into tokens on
        sequentially subsequent calls.  Returns NULL when no
        non-separator characters remain.
        'subsequent' calls are calls with first argument == NULL.
   =============================================================================
*/

#define NULL    (char *)0

extern int strspn(char *string, char *charset);
extern char *strpbrk(char *string, char *brkset);

char *strtok(char *string, char *sepset)
{
        register char *p, *q, *r;
        static char *savept;

        /* first or subsequent call ? */

        p = (string == NULL) ? savept : string;

        if (p == 0)              /* return if no tokens remain */
                return(NULL);

        q = p + strspn(p, sepset);      /* skip leading separators */

        if (*q == '\0')          /* return if no tokens remain */
                return(NULL);

        if ((r = strpbrk(q, sepset)) == NULL)    /* move past token */
                savept = 0;     /* indicate this is last token */
        else {
                *r = '\0';
                savept = ++r;
        }

        return(q);
}