# File lib/nokogiri/html4/document.rb, line 171
def parse(string_or_io, url = nil, encoding = nil, options = XML::ParseOptions::DEFAULT_HTML)
  options = Nokogiri::XML::ParseOptions.new(options) if Integer === options
  yield options if block_given?

  url ||= string_or_io.respond_to?(:path) ? string_or_io.path : nil

  if string_or_io.respond_to?(:encoding)
    unless string_or_io.encoding.name == "ASCII-8BIT"
      encoding ||= string_or_io.encoding.name
    end
  end

  if string_or_io.respond_to?(:read)
    if string_or_io.is_a?(Pathname)
      # resolve the Pathname to the file and open it as an IO object, see #2110
      string_or_io = string_or_io.expand_path.open
      url ||= string_or_io.path
    end

    unless encoding
      # Libxml2's parser has poor support for encoding
      # detection.  First, it does not recognize the HTML5
      # style meta charset declaration.  Secondly, even if it
      # successfully detects an encoding hint, it does not
      # re-decode or re-parse the preceding part which may be
      # garbled.
      #
      # EncodingReader aims to perform advanced encoding
      # detection beyond what Libxml2 does, and to emulate
      # rewinding of a stream and make Libxml2 redo parsing
      # from the start when an encoding hint is found.
      string_or_io = EncodingReader.new(string_or_io)
      begin
        return read_io(string_or_io, url, encoding, options.to_i)
      rescue EncodingFound => e
        encoding = e.found_encoding
      end
    end
    return read_io(string_or_io, url, encoding, options.to_i)
  end

  # read_memory pukes on empty docs
  if string_or_io.nil? || string_or_io.empty?
    return encoding ? new.tap { |i| i.encoding = encoding } : new
  end

  encoding ||= EncodingReader.detect_encoding(string_or_io)

  read_memory(string_or_io, url, encoding, options.to_i)
end

# File lib/nokogiri/html4/document.rb, line 148
def fragment(tags = nil)
  DocumentFragment.new(self, tags, root)
end

# File lib/nokogiri/html4/document.rb, line 12
def meta_encoding
  if (meta = at_xpath("//meta[@charset]"))
    meta[:charset]
  elsif (meta = meta_content_type)
    meta["content"][/charset\s*=\s*([\w-]+)/i, 1]
  end
end

# File lib/nokogiri/html4/document.rb, line 36
def meta_encoding=(encoding)
  if (meta = meta_content_type)
    meta["content"] = format("text/html; charset=%s", encoding)
    encoding
  elsif (meta = at_xpath("//meta[@charset]"))
    meta["charset"] = encoding
  else
    meta = XML::Node.new("meta", self)
    if (dtd = internal_subset) && dtd.html5_dtd?
      meta["charset"] = encoding
    else
      meta["http-equiv"] = "Content-Type"
      meta["content"] = format("text/html; charset=%s", encoding)
    end

    if (head = at_xpath("//head"))
      head.prepend_child(meta)
    else
      set_metadata_element(meta)
    end
    encoding
  end
end

# File lib/nokogiri/html4/document.rb, line 141
def serialize(options = {})
  options[:save_with] ||= XML::Node::SaveOptions::DEFAULT_HTML
  super
end

# File lib/nokogiri/html4/document.rb, line 70
def title
  (title = at_xpath("//title")) && title.inner_text
end

# File lib/nokogiri/html4/document.rb, line 85
def title=(text)
  tnode = XML::Text.new(text, self)
  if (title = at_xpath("//title"))
    title.children = tnode
    return text
  end

  title = XML::Node.new("title", self) << tnode
  if (head = at_xpath("//head"))
    head << title
  elsif (meta = (at_xpath("//meta[@charset]") || meta_content_type))
    # better put after charset declaration
    meta.add_next_sibling(title)
  else
    set_metadata_element(title)
  end
end

# File lib/nokogiri/html4/document.rb, line 158
def xpath_doctype
  Nokogiri::CSS::XPathVisitor::DoctypeConfig::HTML4
end