#!/usr/bin/ruby1.8
#
#  yunta83@gmail.com
#  BSD license
#


require 'rubygems'
require 'rfuse_ng'
require 'narray'


class Stat
	attr_accessor :uid,:gid,:mode,:size,:atime,:mtime,:ctime,:dev,:ino,:nlink,:rdev,:blksize,:blocks
	def initialize(mode=0,size=0)
		@mode,@size,@uid,@gid,@atime,@mtime,@ctime,@dev,@ino,@nlink,@rdev,@blksize,@blocks = [mode,size]+[0]*11
	end
end


class XorFS < RFuse::Fuse

	def initialize(mnt,kernelopt,libopt,parts)
		@parts = parts.collect { |part|
			[File.new(part,(part == parts[0] and "r+" or "r")),File.stat(part).size]
		}
		@size = @parts.collect { |x| x[1] }.min
		super(mnt,kernelopt,libopt)
	end

	def readdir(ctx,path,filler,offset,ffi)
		return if offset > 0
		filler.push("data",Stat.new(0100777),0)
	end


	def getattr(ctx,path)
		raise Errno::ENOTDIR.new(path) if path != "/" and path != "/data"
		Stat.new((path == "/" and 040777 or 0100777),(path == "/" and 0 or @size))
	end

	def open(ctx,path,ffi)
	end

	def read(ctx,path,size,offset,fi)
		xor(@parts.collect { |part,partSize| 
			    part.seek(offset)
			    part.read(size)
		    })
	end

	def write(ctx,path,buf,offset,fi)
		@parts[0][0].seek(offset)
		@parts[0][0].write(xor([buf]+@parts[1..-1].collect { |part,partSize| 
					       part.seek(offset)
					       part.read(buf.size)
				       }))
		buf.length
	end

private

	def xor(strings)
		strings[1..-1].inject(NArray.to_na(strings[0],"byte")) { |result,string|
			result ^= NArray.to_na(string,"byte")
		}.to_s
	end

end

if ARGV.size < 2
	puts "minimum 2 parameters needed:"
	puts "\truby xorfs.rb MOUNT_POINT WRITABLE_FILE_OR_DEV [ READABLE_FILE_OR_DEV ]*"
	exit
end

fo = XorFS.new(ARGV[0],["default_permissions"],[],ARGV[1..-1]);

#kernel:  default_permissions,allow_other,kernel_cache,large_read,direct_io
#         max_read=N,fsname=NAME
#library: debug,hard_remove

Signal.trap("TERM") do
	fo.exit
	fo.unmount
end

begin
	fo.loop
rescue
	print "Error:" + $!
end