#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

unsigned char next(
		unsigned char lfsr,         // le registre
		unsigned char retroaction_f // les bits selectionnés par la 
		)                           // fonction de retroaction
{
	// TODO
}

int main(int argc, char *argv[])
{
	int fd_in,fd_out;
	unsigned char w,buf,f;


	assert(argc >= 4);
	fd_in = open(argv[1],O_RDONLY);
	fd_out = open(argv[2],O_WRONLY|O_TRUNC|O_CREAT,0600);
	w = (unsigned char)strtol(argv[3],NULL,0);
	f = ; // TODO
	
	while(1){
		ssize_t nb = read(fd_in,&buf,1);
		if (nb <=0)
			break;
		buf ^= w;
		write(fd_out,&buf,1);
		w=next(w,f);
	}
	return 0;
}