tp

DEV4.4/TP1/Ex1/lfsr.c

@@ -0,0 +1,47 @@
+#include <stdio.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#define MASK_BIT_7      0x80
+#define MASK_BIT_6      0x40
+#define MASK_BIT_5      0x20
+#define MASK_BIT_4      0x10
+#define MASK_BIT_3      0x08
+#define MASK_BIT_2      0x04
+#define MASK_BIT_1      0x02
+#define MASK_BIT_0      0x01
+
+
+unsigned char next(unsigned char lfsr)
+{
+	lfsr = (lfsr << 1);
+	if(__builtin_parity(lfsr)==0){
+		lfsr ^= 1 << 0;
+	}
+	return lfsr;
+
+}
+
+int main(int argc, char *argv[])
+{
+	int fd_in,fd_out;
+	unsigned char w,buf;;
+
+
+	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);
+
+	while(1){
+		ssize_t nb = read(fd_in,&buf,1);
+		if (nb <=0)
+			break;
+		buf ^= w;
+		write(fd_out,&buf,1);
+		w=next(w);
+	}
+	return 0;
+}