# File lib/parts.rb, line 40
    def initialize(boundary, name, io)
      file_length = io.respond_to?(:length) ?  io.length : File.size(io.local_path)
      @head = build_head(boundary, name, io.original_filename, io.content_type, file_length)
      @foot = "\r\n"
      @length = @head.length + file_length + @foot.length
      @io = CompositeReadIO.new(StringIO.new(@head), io, StringIO.new(@foot))
    end