# File lib/rubygems/package/tar_reader.rb, line 92
  def rewind
    if @init_pos == 0 then
      raise Gem::Package::NonSeekableIO unless @io.respond_to? :rewind
      @io.rewind
    else
      raise Gem::Package::NonSeekableIO unless @io.respond_to? :pos=
      @io.pos = @init_pos
    end
  end