    # File lib/rubygems/package/tar_header.rb, line 150
      def initialize(vals)
        unless vals[:name] && vals[:size] && vals[:prefix] && vals[:mode] then
          raise ArgumentError, ":name, :size, :prefix and :mode required"
        end

        vals[:uid] ||= 0
        vals[:gid] ||= 0
        vals[:mtime] ||= 0
        vals[:checksum] ||= ""
        vals[:typeflag] ||= "0"
        vals[:magic] ||= "ustar"
        vals[:version] ||= "00"
        vals[:uname] ||= "wheel"
        vals[:gname] ||= "wheel"
        vals[:devmajor] ||= 0
        vals[:devminor] ||= 0

        FIELDS.each do |name|
          instance_variable_set "@#{name}", vals[name]
        end

        @empty = vals[:empty]
      end