public synchronized void mark(int readLimit) {
        try {
            markPos = getFilePointer();
        } catch (IOException e) {
            markPos = -1L;
        }
    }
Marks the current file position for later return using
the <code>reset()</code> method.
plugins/svg-plugin/batik-codec-fix/src/main/java/org/apache/batik/ext/awt/image/codec/util/SeekableStream.java