unescapeHTML

# File lib/cgi/util.rb, line 40
  def CGI::unescapeHTML(string)
    enc = string.encoding
    if [Encoding::UTF_16BE, Encoding::UTF_16LE, Encoding::UTF_32BE, Encoding::UTF_32LE].include?(enc)
      return string.gsub(Regexp.new('&(amp|quot|gt|lt|#[0-9]+|#x[0-9A-Fa-f]+);'.encode(enc))) do
        case $1.encode("US-ASCII")
        when 'amp'                 then '&'.encode(enc)
        when 'quot'                then '"'.encode(enc)
        when 'gt'                  then '>'.encode(enc)
        when 'lt'                  then '<'.encode(enc)
        when /\A#0*(\d+)\z/        then $1.to_i.chr(enc)
        when /\A#x([0-9a-f]+)\z/  then $1.hex.chr(enc)
        end
      end
    end
    asciicompat = Encoding.compatible?(string, "a")
    string.gsub(/&(amp|quot|gt|lt|\#[0-9]+|\#x[0-9A-Fa-f]+);/) do
      match = $1.dup
      case match
      when 'amp'                 then '&'
      when 'quot'                then '"'
      when 'gt'                  then '>'
      when 'lt'                  then '<'
      when /\A#0*(\d+)\z/
        n = $1.to_i
        if enc == Encoding::UTF_8 or
          enc == Encoding::ISO_8859_1 && n < 256 or
          asciicompat && n < 128
          n.chr(enc)
        else
          "&##{$1};"
        end
      when /\A#x([0-9a-f]+)\z/
        n = $1.hex
        if enc == Encoding::UTF_8 or
          enc == Encoding::ISO_8859_1 && n < 256 or
          asciicompat && n < 128
          n.chr(enc)
        else
          "&#x#{$1};"
        end
      else
        "&#{match};"
      end
    end
  end