class Mail::ContentDispositionField

def self.singular?
  true
end

def decoded
  p = "; #{parameters.decoded}" if parameters.length > 0
  "#{disposition_type}#{p}"
end

def disposition_type
  element.disposition_type
end

def element
  @element ||= Mail::ContentDispositionElement.new(value)
end

def encoded
  p = ";\r\n\s#{parameters.encoded}" if parameters.length > 0
  "#{name}: #{disposition_type}#{p}\r\n"
end

def filename
  @filename ||= parameters['filename'] || parameters['name']
end

def initialize(value = nil, charset = nil)
  super ensure_filename_quoted(value), charset
end

def parameters
  @parameters = ParameterHash.new
  element.parameters.each { |p| @parameters.merge!(p) } unless element.parameters.nil?
  @parameters
end