class Nokogiri::HTML::Document::EncodingReader

def self.detect_encoding(chunk)
  m = chunk.match(/\A(<\?xml[ \t\r\n]+[^>]*>)/) and
    return Nokogiri.XML(m[1]).encoding
  if Nokogiri.jruby?
    m = chunk.match(/(<meta\s)(.*)(charset\s*=\s*([\w-]+))(.*)/i) and
      return m[4]
    catch(:encoding_found) {
      Nokogiri::HTML::SAX::Parser.new(JumpSAXHandler.new(:encoding_found)).parse(chunk)
      nil
    }
  else
    handler = SAXHandler.new
    parser = Nokogiri::HTML::SAX::PushParser.new(handler)
    parser << chunk rescue Nokogiri::SyntaxError
    handler.encoding
  end
end