struct threadsafefile: lock, file {}

class worker: thread {
    threadsafefile* file
	run
		file.lock()
		file.append("stuff")
		file.unlock()
}

main
	threadsafefile a("path", "rw", IO_APPEND)
	for i = 0, 255
	   for y 0, 255 do
		  worker b
		  b.file = a
		  b.run()