Gem::Package::Old#extract_files

# File tmp/rubies/ruby-4.1.0-preview1/lib/rubygems/package/old.rb, line 52
def extract_files(destination_dir)
  verify

  errstr = "Error reading files from gem"

  @gem.with_read_io do |io|
    read_until_dashes io # spec
    header = file_list io
    raise Gem::Exception, errstr unless header

    # install_location expects an already-resolved destination dir
    destination_dir = File.realpath(destination_dir)

    header.each do |entry|
      full_name = entry["path"]

      destination = install_location full_name, destination_dir

      file_data = String.new

      read_until_dashes io do |line|
        file_data << line
      end

      file_data = file_data.strip.unpack1("m")
      file_data = Zlib::Inflate.inflate file_data

      raise Gem::Package::FormatError, "#{full_name} in #{@gem} is corrupt" if
        file_data.length != entry["size"].to_i

      FileUtils.mkdir_p File.dirname(destination), mode: dir_mode && 0o755

      verify_extraction_dir File.dirname(destination), destination_dir

      FileUtils.rm_rf destination

      File.open destination, "wb", file_mode(entry["mode"]) do |out|
        out.write file_data
      end

      verbose destination
    end
  end
rescue Zlib::DataError
  raise Gem::Exception, errstr
end