coroutine.c

void yield(coroutine* c, ...)
{
    va_list ap;
    void *arg;

    c->arg_ptr = (void **)(c->arg_buf);

    va_start(ap, c);
    do {
		    arg = va_arg(ap, void *);
		    *c->arg_ptr++ = arg;
    } while(arg != NULL);
    va_end(ap);

	if(!setjmp(c->callee_context)) {
        longjmp(c->caller_context, WORKING);
    }
}

int next(coroutine *c, void (*on_next)(coroutine *c, va_list *ap), ...)
{
	int ret = setjmp(c->caller_context);
    if(!ret) {
        longjmp(c->callee_context, WORKING);
    } else {
        va_list ap;
        
        va_start(ap, on_next);
        on_next(c, &ap);
        va_end(ap);
        return ret == WORKING;
    }
}

void on_next(coroutine *c, va_list *ap)
{
    int *x, *y;

    x = va_arg(*ap, int *);
    y = va_arg(*ap, int *);
    *x = *(int *)c->arg_buf[0];
    *y = *(int *)c->arg_buf[1];

}