rewind

static VALUE
argf_rewind(VALUE argf)
{
    VALUE ret;
    int old_lineno;

    if (!next_argv()) {
        rb_raise(rb_eArgError, "no stream to rewind");
    }
    ARGF_FORWARD(0, 0);
    old_lineno = RFILE(ARGF.current_file)->fptr->lineno;
    ret = rb_io_rewind(ARGF.current_file);
    if (!global_argf_p(argf)) {
        ARGF.last_lineno = ARGF.lineno -= old_lineno;
    }
    return ret;
}