module Nokogiri

def parse string, url = nil, encoding = nil, options = nil
  if string.respond_to?(:read) ||
      /^\s*<(?:!DOCTYPE\s+)?html[\s>]/i === string[0, 512]
    # Expect an HTML indicator to appear within the first 512
    # characters of a document. (<?xml ?> + <?xml-stylesheet ?>
    # shouldn't be that long)
    Nokogiri.HTML(string, url, encoding,
      options || XML::ParseOptions::DEFAULT_HTML)
  else
    Nokogiri.XML(string, url, encoding,
      options || XML::ParseOptions::DEFAULT_XML)
  end.tap { |doc|
    yield doc if block_given?
  }
end