Ruby script to apply IPS patches.

ruby-ips.rb

#!/usr/bin/env ruby
# -*- encoding: US-ASCII -*-

# ruby-ips.rb --Kernigh, March 2009
# This program is in the public domain and has no copyright.

require 'optparse'

filename = nil
sflag = false

opts = OptionParser.new do |opts|
	opts.banner = "usage: #{$0} [-s] [-f file] patch..."

	opts.on("-f FILE", "Apply patches to FILE") do |f|
		filename = f
	end

	opts.on("-s", "Work silently") do |l|
		sflag = true
	end
end

opts.parse!

# usage message if no arguments
if ARGV.size == 0
	puts opts
	exit 0
end

if sflag && (not filename)
	$stderr.puts "#{$0}: nothing to do"
	exit 1
end

# compatibility with Ruby before 1.8.7
unless 3.respond_to? :ord
	# with Ruby 1.8, "x"[0] is Fixnum
	# with Ruby 1.9, "x"[0] is String, "x"[0].ord is Fixnum
	class Integer
		def ord
			self
		end
	end
end

# subroutines
def unpack2(bytes)
	(bytes[0].ord << 8) + bytes[1].ord
end
def unpack3(bytes)
	(bytes[0].ord << 16) + (bytes[1].ord << 8) + bytes[2].ord
end
def hex(num)
	"0x#{num.to_s(16)} (#{num})"
end

# start work
file = open(filename, File::RDWR) if filename

ARGV.each do |patchname|

	# provide pinfo, pwarn for this patch
	pinfo = if sflag
		lambda { |m| }
	else
		$stdout.puts "#{patchname}:"
		lambda { |m| $stdout.puts "  #{m}" }
	end
	pwarn = lambda { |m| $stderr.puts "#{patchname}: #{m}" }

	# open patch
	patch = open(patchname, File::RDONLY)

	# check magic bytes
	unless patch.read(5) == "PATCH"
		pwarn.call "bad magic bytes, not an IPS patch"
		exit 1
	end

	# lambda to read patch and check number of bytes
	pread = lambda do |count|
		bytes = patch.read(count)
		if bytes.length < count
			pwarn.call "read #{bytes.length} bytes from patch, " +
			    "expected #{count} bytes"
			pwarn.call "unexpected end of patch file"
			exit 1
		end
		bytes
	end

	# process each record
	while true
		offset = pread.call(3)

		# "EOF" marks the end of patch
		if offset == "EOF"
			# count the remaining bytes in the file
			rem = patch.stat.size - patch.pos

			case rem
			when 0
				pinfo.call "end of patch"
			when 3
				# truncate support, as in Lunar IPS
				tru = unpack3(pread.call(3))
				pinfo.call "truncate to #{hex(tru)} bytes"
				file.truncate(tru) if filename
			else
				pwarn.call "unexpected data after end of " +
				    "patch, #{hex(rem)} bytes ..."
				pwarn.call "... problem with offset " +
				    "\"EOF\" #{hex("EOF")}?"
				exit 1
			end

			break
		end

		offset = unpack3(offset)
		length = unpack2(pread.call(2))
		case length
		when 0
			# RLE support
			length = unpack2(pread.call(2))
			byte = pread.call(1)

			pinfo.call "patch to file offset #{hex(offset)}, " +
			    "length #{hex(length)}, RLE"
			if filename
				file.pos = offset
				file.write(byte * length)
			end
		else
			pinfo.call "patch to file offset #{hex(offset)}, " +
			    "length #{hex(length)}"
			if filename
				file.pos = offset
				file.write(pread.call(length))
			else
				pread.call(length)
			end
		end
	end

	patch.close
end

file.close if filename