CD format visualizer

cdvisual.rb

#!/usr/bin/env ruby

NONE = 0 # N/A
MODE1 = 1 # CD-ROM Mode 1
MODE2 = 2 # CD-ROM Mode 2 (not XA)
MODE2_FORM1 = 3 # CD-ROM XA Form 1
MODE2_FORM2 = 4 # CD-ROM XA Form 2
OTHER = 5 # Other (e.g. CD-DA)

# CD-ROM sync header
CDROM_SYNC = [0x00, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00]

def get_mode_string(mode)
  case mode
  when NONE
    'None (maybe bug?)'
  when MODE1
    'CD-ROM Mode 1'
  when MODE2
    'CD-ROM Mode 2 (not CD-ROM XA)'
  when MODE2_FORM1
    'CD-ROM XA Form 1'
  when MODE2_FORM2
    'CD-ROM XA Form 2'
  when OTHER
    'Other (e.g. CD-DA)'
  else
    '(maybe bug?)'
  end
end

name = ARGV[0]
size = File.size(name)

if size % 2352 != 0 then
  puts 'Error: Not a CD raw image file!'
  exit 1
end

f = File.open(name, 'rb')

mode = NONE
prev_mode = NONE
sectors = size / 2352

sectors.times do |i|
  f.pos = i * 2352

  header = f.read(24).bytes

  if header.first(12) == CDROM_SYNC then
    case header[15]
    when 0x01
      mode = MODE1
    when 0x02
      if header[16..19] == header[20..23] then
        if header[18] & 0x04 != 0 then
          mode = MODE2_FORM2
        else
          mode = MODE2_FORM1
        end
      else
        mode = MODE2
      end
    else
      mode = OTHER
    end
  else
    mode = OTHER
  end

  if prev_mode != mode then
    puts 'Sector 0x%X : %s' % [i, get_mode_string(mode)]
  end

  prev_mode = mode
end

f.close