FON file splitter

extract.rb

#!/usr/bin/env ruby

require "fileutils"

module MachineIO
	def read_word
		read(2).unpack("v")[0]
	end
	
	def read_dword
		read(4).unpack("V")[0]
	end
end

def parse_ne(io)
	contents = []
	
	raise "Bad MZ signature" if io.read(2) != "MZ"
	
	io.seek 0x3C
	ne_offset = io.read_dword
	
	io.seek ne_offset
	raise "Bad NE signature" if io.read(2) != "NE"
	
	io.seek ne_offset + 0x24
	res_offset = ne_offset + io.read_word
	
	io.seek res_offset
	
	shift = io.read_word
	loop do
		type = io.read_word
		break if type == 0
		
		count = io.read_word
		
		io.seek 4, IO::SEEK_CUR
		
		for i in 0...count
			start = io.read_word << shift
			size = io.read_word << shift
			flags = io.read_word
			id = io.read_word
			handle = io.read_word
			usage = io.read_word
		
			if type == 0x8008
				contents << [ start, size ]
			end
		end
	end
	
	contents
end

Dir.mkdir "expanded" unless File.exists? "expanded"
Dir.mkdir "fonts" unless File.exists? "fonts"

for file in Dir.entries "compressed"
	next unless File.file? File.join("compressed", file)
	
	expanded = nil
	compressed = nil
	begin
		expanded = File.open File.join("expanded", file), "wb"
		compressed = File.open File.join("compressed", file), "rb"
		
		child = Process.spawn "msexpand", in: compressed, out: expanded, err: :err
		status = Process.wait child
		
		raise "Expanding of #{file} failed" unless $?.exitstatus == 0
	ensure
		expanded.close unless expanded.nil?
		compressed.close unless compressed.nil?
	end
end

for filename in Dir.entries "expanded"
	file = File.join "expanded", filename
	next unless File.file? file
	
	File.open(file, "rb") do |io|
		io.extend MachineIO
	
		contents = parse_ne io
		
		split = File.join "fonts", filename.split('.')[0...-1]
		
		contents.each_with_index do |(offset, size), idx|
			File.open("#{split}_#{idx}.fnt", "wb") do |dest|
				io.seek offset
				IO.copy_stream io, dest, size
			end
		end
	end
end