corrupter

main.rb

#!/usr/bin/env ruby

if ARGV.length != 1
	puts "Please call this as \"ruby corrupt.rb <input file>\""
	exit
end

def get_char
	state = `stty -g`
	`stty raw -echo -icanon isig`
	return $stdin.getc.chr
ensure
	`stty #{state}`
end

$startByte = 10000
$corruptionType = 0
$corruptionRate = 1000
$corruptionChance = 1000
$byteOffset = 1

def corrupt()
	inputFile = File.open("#{ARGV[0]}", "rb")
	outputFile = File.open("Corrupted_#{ARGV[0]}", "wb")
	currentByte = 0
	inputFile.each_byte do |c|
		willCorrupt = false
		if $corruptionType == 0
			willCorrupt = (currentByte % $corruptionRate == 0)
		elsif $corruptionType == 1
			willCorrupt = (rand < (1.0/$corruptionChance))
		end

		if willCorrupt
			tempByte = c + $byteOffset*(rand(2) == 1 ? 1 : -1)
			if tempByte > 255
				tempByte = tempByte % 255
			end
			if tempByte < 0
				tempByte = -tempByte % 255
			end
			outputFile.write(tempByte.chr)
		else
			outputFile.write(c.chr)
		end
		currentByte += 1
	end
	outputFile.close
	inputFile.close
end

loop do
	system("clear")
	puts "Current file: #{ARGV[0]}\n\n"
	puts "Starting byte (s): #{$startByte}\n\n"
	puts "Corruption type (t): #{%w(every-n chance)[$corruptionType]}\n\n"
	puts ("Corruption " + ["rate (r): #{$corruptionRate}", "chance (c): #{$corruptionChance}"][$corruptionType] + "\n\n")
	puts "Byte offset (b): #{$byteOffset}\n\n"
	puts "Begin corruption with o"
	case get_char
	when ?s
		system("clear")
		puts "New starting byte (old was #{$startByte}): "
		$startByte = $stdin.gets.chomp.to_i
	when ?t
		system("clear")
		puts "Corruption types (old was #{$corruptionType}):\n0 - every-n\n1 - chance"
		$corruptionType = $stdin.gets.chomp.to_i
	when ?r
		system("clear")
		puts "New corruption rate (old was #{$corruptionRate}): "
		$corruptionRate = $stdin.gets.chomp.to_i
	when ?c
		system("clear")
		puts "New corruption chance (old was 1/#{$corruptionChance}): "
		print "1/"
		$corruptionChance = $stdin.gets.chomp.to_i
	when ?b
		system("clear")
		puts "New byte offset (old was #{$byteOffset}): "
		$byteOffset = $stdin.gets.chomp.to_i
	when ?o
		system("clear")
		puts "Beginning corruption, outputting to Corrupted_#{ARGV[0]}"
		corrupt
		puts "Corruption complete, press any key to return"
		get_char
	end
end