IO#wait

static VALUE
io_wait(int argc, VALUE *argv, VALUE io)
{
    VALUE timeout = Qundef;
    rb_io_event_t events = 0;

    if (argc != 2 || (RB_SYMBOL_P(argv[0]) || RB_SYMBOL_P(argv[1]))) {
        for (int i = 0; i < argc; i += 1) {
            if (RB_SYMBOL_P(argv[i])) {
                events |= wait_mode_sym(argv[i]);
            }
            else if (timeout == Qundef) {
                rb_time_interval(timeout = argv[i]);
            }
            else {
                rb_raise(rb_eArgError, "timeout given more than once");
            }
        }
        if (timeout == Qundef) timeout = Qnil;
    }
    else /* argc == 2 */ {
        events = RB_NUM2UINT(argv[0]);
        timeout = argv[1];
    }

    if (events == 0) {
        events = RUBY_IO_READABLE;
    }

    if (events & RUBY_IO_READABLE) {
        rb_io_t *fptr = NULL;
        RB_IO_POINTER(io, fptr);

        if (rb_io_read_pending(fptr)) {
            return Qtrue;
        }
    }

    return io_wait_event(io, events, timeout);
}