Unpack PackFile

unpackfile.rb

def die(message)
  puts message
  exit
end

def validate(what, actual, expected)
  die "Invalid file format: #{what} should be #{expected} but got #{actual}" if
    actual != expected
end

def main()
  validate 'Magic number', ARGF.read(8), 'PackFile'
  validate 'Padding', ARGF.read(4), '    '
  file_count = ARGF.read(4).unpack('L<')[0]
  file_headers = []
  (1..file_count).each do |n|
    h = {}
    h[:name] = ARGF.read(16).unpack('Z*')[0]
    h[:offset] = ARGF.read(4).unpack('L<')[0]
    h[:size] = ARGF.read(4).unpack('L<')[0]
    validate "Padding ##{n}", ARGF.read(8), "\x00" * 8
    file_headers << h
  end

  file_headers.each do |h|
    puts "Extracting #{h[:name]} (offset #{h[:offset]} / size #{h[:size]})"
    File.open(h[:name], 'wb') do |io|
      io.write(ARGF.read(h[:size]))
    end
  end
end

main()