old.rb

#--
# Copyright 2006 by Chad Fowler, Rich Kilmer, Jim Weirich and others.
# All rights reserved.
# See LICENSE.txt for permissions.
#++

##
# The format class knows the guts of the ancient .gem file format and provides
# the capability to read such ancient gems.
#
# Please pretend this doesn't exist.

class Gem::Package::Old < Gem::Package

  undef_method :spec=

  ##
  # Creates a new old-format package reader for +gem+.  Old-format packages
  # cannot be written.

  def initialize gem
    require 'fileutils'
    require 'zlib'
    Gem.load_yaml

    @contents        = nil
    @gem             = gem
    @security_policy = nil
    @spec            = nil
  end

  ##
  # A list of file names contained in this gem

  def contents
    verify

    return @contents if @contents

    open @gem, 'rb' do |io|
      read_until_dashes io # spec
      header = file_list io

      @contents = header.map { |file| file['path'] }
    end
  end

  ##
  # Extracts the files in this package into +destination_dir+

  def extract_files destination_dir
    verify

    errstr = "Error reading files from gem"

    open @gem, 'rb' do |io|
      read_until_dashes io # spec
      header = file_list io
      raise Gem::Exception, errstr unless header

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

        destination = install_location full_name, destination_dir

        file_data = ''

        read_until_dashes io do |line|
          file_data << line
        end

        file_data = file_data.strip.unpack("m")[0]
        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.rm_rf destination

        FileUtils.mkdir_p File.dirname destination

        open destination, 'wb', entry['mode'] do |out|
          out.write file_data
        end

        say destination if Gem.configuration.really_verbose
      end
    end
  rescue Zlib::DataError
    raise Gem::Exception, errstr
  end

  ##
  # Reads the file list section from the old-format gem +io+

  def file_list io # :nodoc:
    header = ''

    read_until_dashes io do |line|
      header << line
    end

    YAML.load header
  end

  ##
  # Reads lines until a "---" separator is found

  def read_until_dashes io # :nodoc:
    while (line = io.gets) && line.chomp.strip != "---" do
      yield line if block_given?
    end
  end

  ##
  # Skips the Ruby self-install header in +io+.

  def skip_ruby io # :nodoc:
    loop do
      line = io.gets

      return if line.chomp == '__END__'
      break unless line
    end

    raise Gem::Exception, "Failed to find end of ruby script while reading gem"
  end

  ##
  # The specification for this gem

  def spec
    verify

    return @spec if @spec

    yaml = ''

    open @gem, 'rb' do |io|
      skip_ruby io
      read_until_dashes io do |line|
        yaml << line
      end
    end

    yaml_error = if RUBY_VERSION < '1.9' then
                   YAML::ParseError
                 elsif YAML::ENGINE.yamler == 'syck' then
                   YAML::ParseError
                 else
                   YAML::SyntaxError
                 end

    begin
      @spec = Gem::Specification.from_yaml yaml
    rescue yaml_error => e
      raise Gem::Exception, "Failed to parse gem specification out of gem file"
    end
  rescue ArgumentError => e
    raise Gem::Exception, "Failed to parse gem specification out of gem file"
  end

  ##
  # Raises an exception if a security policy that verifies data is active.
  # Old format gems cannot be verified as signed.

  def verify
    return true unless @security_policy

    raise Gem::Security::Exception,
          'old format gems do not contain signatures and cannot be verified' if
      @security_policy.verify_data

    true
  end

end