Module: Ultra7::MIME

Defined in:
lib/ultra7/mime.rb

Class Method Summary collapse

Class Method Details

.decode_utf7(text, options = {encoding: nil}) ⇒ String

Parse the given UTF-7 encoded-word text and return the corresponding decoded value.

If the :encoding name is not specified in the options hash, then the resulting string will use the default Encoding.default_external encoding.

Parameters:

  • text (String) —

    UTF-7 encoded-word text

  • options (Hash) (defaults to: {encoding: nil})

Returns:

  • (String) —

    UTF-7 decoded value

Raises:

  • (ArgumentError) —

    if text other than UTF-7 is passed in, or the named :encoding cannot be found



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# File 'lib/ultra7/mime.rb', line 23

def self.decode_utf7(text, options={encoding: nil})
  # only deal with UTF-7 encoding
  text.scan(/=\?(.*)\?[q]\?/im).each {
    e = $1
    if e and !(e=~/utf\-7/i)
      raise ArgumentError.new("Cannot decode #{e} as UTF-7!")
    end
  }

  # remove any opening charset and Q-encoding start/end markers
  # for MIME encoded words
  text = text.gsub(/\?=/m, '').gsub(/=\?[^?]*utf\-7\?[q]\?/im, '')

  enc = options[:encoding].nil? \
    ? Encoding.default_external \
    : Encoding.find(options[:encoding])
  
  return text.gsub(/\+(.*?)-/mn) {
    if $1.empty?
      "+"
    else
      base64 = $1
      pad = base64.length % 4
      if pad > 0
        base64 << ("=" * (4-pad))
      end
      base64.unpack("m").first.unpack("n*").pack("U*")
    end
  }.encode(enc)
end