private void unread(char[] ch, int length) throws SAXException {
        if (length < readBufferPos) {
            readBufferPos -= length;
        } else {
            pushCharArray(null, ch, 0, length);
        }
    }
Push a char array back onto the current input stream.
<p>
NOTE: you must <em>never</em> push back characters that you haven't
actually read: use pushString () instead.

@see #readCh
@see #unread (char)
@see #readBuffer
@see #pushString
src/nu/validator/gnu/xml/aelfred2/XmlParser.java