code: public void evaluate(
            XPathContext xctxt, FastStringBuffer buf, int context, org.apache.xml.utils.PrefixResolver nsNode)
              throws javax.xml.transform.TransformerException
    {
  
      XObject xobj = m_xpath.execute(xctxt, context, nsNode);
  
      if (null != xobj)
      {
        xobj.appendToFsb(buf);
      }
    }
docs: Write the value into the buffer.
  
  @param xctxt An XPathContext object, providing infomation specific
  to this invocation and this thread. Maintains SAX state, variables,
  error handler and  so on, so the transformation/XPath object itself
  can be simultaneously invoked from multiple threads.
  @param buf Buffer to write into.
  @param context The current source tree context.
  @param nsNode The current namespace context (stylesheet tree context).
  
  @throws javax.xml.transform.TransformerException