module Nokogiri::HTML5

def reencode(body, content_type = nil)


http://www.w3.org/TR/html5/syntax.html#determining-the-character-encoding
http://bugs.ruby-lang.org/issues/2567

the HTML5 standard.
this lead, Nokogiri::HTML5 attempts to do likewise, while attempting to more closely follow
Accordingly, Nokogiri::HTML4::Document.parse provides limited encoding detection. Following

the Gumbo parser *only* supports utf-8.
consumers of HTML as the default for HTML is iso-8859-1, most "good" producers use utf-8, and
default_ by the Ruby Net::HTTP library. This being said, it is a very real problem for
Charset sniffing is a complex and controversial topic that understandably isn't done _by 
def reencode(body, content_type = nil)
  if body.encoding == Encoding::ASCII_8BIT
    encoding = nil
    # look for a Byte Order Mark (BOM)
    initial_bytes = body[0..2].bytes
    if initial_bytes[0..2] == [0xEF, 0xBB, 0xBF]
      encoding = Encoding::UTF_8
    elsif initial_bytes[0..1] == [0xFE, 0xFF]
      encoding = Encoding::UTF_16BE
    elsif initial_bytes[0..1] == [0xFF, 0xFE]
      encoding = Encoding::UTF_16LE
    end
    # look for a charset in a content-encoding header
    if content_type
      encoding ||= content_type[/charset=["']?(.*?)($|["';\s])/i, 1]
    end
    # look for a charset in a meta tag in the first 1024 bytes
    unless encoding
      data = body[0..1023].gsub(/<!--.*?(-->|\Z)/m, "")
      data.scan(/<meta.*?>/im).each do |meta|
        encoding ||= meta[/charset=["']?([^>]*?)($|["'\s>])/im, 1]
      end
    end
    # if all else fails, default to the official default encoding for HTML
    encoding ||= Encoding::ISO_8859_1
    # change the encoding to match the detected or inferred encoding
    body = body.dup
    begin
      body.force_encoding(encoding)
    rescue ArgumentError
      body.force_encoding(Encoding::ISO_8859_1)
    end
  end
  body.encode(Encoding::UTF_8)
end