    /*
     * call-seq:
     *  read_memory(string, url, encoding, options)
     *
     * Create a new document from a String
     */
    static VALUE read_memory( VALUE klass,
                              VALUE string,
                              VALUE url,
                              VALUE encoding,
                              VALUE options )
    {
      const char * c_buffer = StringValuePtr(string);
      const char * c_url    = (url == Qnil) ? NULL : StringValuePtr(url);
      const char * c_enc    = (encoding == Qnil) ? NULL : StringValuePtr(encoding);
      int len               = RSTRING_LEN(string);
      VALUE error_list      = rb_ary_new();

      xmlInitParser();
      xmlResetLastError();
      xmlSetStructuredErrorFunc((void *)error_list, Nokogiri_error_array_pusher);
      xmlDocPtr doc = xmlReadMemory(c_buffer, len, c_url, c_enc, NUM2INT(options));
      xmlSetStructuredErrorFunc(NULL, NULL);

      if(doc == NULL) {
        xmlFreeDoc(doc);

        xmlErrorPtr error = xmlGetLastError();
        if(error)
          rb_funcall(rb_mKernel, rb_intern("raise"), 1,
              Nokogiri_wrap_xml_syntax_error((VALUE)NULL, error)
          );
        else
          rb_raise(rb_eRuntimeError, "Could not parse document");

        return Qnil;
      }

      VALUE document = Nokogiri_wrap_xml_document(klass, doc);
      rb_funcall(document, rb_intern("errors="), 1, error_list);
      return document;
    }