Uploading files in Ruby on Rails

BOUNDARY = "AaB03x"

def encode_multipartformdata(parameters = {})
  ret = String.new
  parameters.each do |key, value|
    unless value.empty?
      ret << "rn--" << BOUNDARY << "rn"
      ret << "Content-Disposition: form-data; name="#{key}"rnrn"
      ret << value
    end
  end
  ret << "rn--" << BOUNDARY << "--rn"
end