closed?

/*
 *  call-seq:
 *     ios.closed?    => true or false
 *  
 *  Returns <code>true</code> if <em>ios</em> is completely closed (for
 *  duplex streams, both reader and writer), <code>false</code>
 *  otherwise.
 *     
 *     f = File.new("testfile")
 *     f.close         #=> nil
 *     f.closed?       #=> true
 *     f = IO.popen("/bin/sh","r+")
 *     f.close_write   #=> nil
 *     f.closed?       #=> false
 *     f.close_read    #=> nil
 *     f.closed?       #=> true
 */

static VALUE
rb_io_closed(io)
    VALUE io;
{
    OpenFile *fptr;

    fptr = RFILE(io)->fptr;
    rb_io_check_initialized(fptr);
    return (fptr->f || fptr->f2)?Qfalse:Qtrue;
}