--- a/ffstools/tiffs-rd/basics.c	Sat Jan 25 23:56:47 2014 +0000
+++ b/ffstools/tiffs-rd/basics.c	Sun Jan 26 00:34:22 2014 +0000
@@ -24,7 +24,7 @@
 extern int index_blk_num, root_node_no;
 extern int verbose;
 
-u_char *image;
+u8 *image, *inode_block;
 
 read_ffs_image()
 {
@@ -72,3 +72,76 @@
 	}
 	exit(0);
 }
+
+find_inode_block()
+{
+	int i, abcnt;
+	u8 *ptr;
+
+	if (index_blk_num >= 0) {
+		if (index_blk_num >= total_blocks) {
+			fprintf(stderr,
+				"invalid block # given with the -a option\n");
+			exit(1);
+		}
+		ptr = image + index_blk_num * eraseblk_size;
+		if (bcmp(ptr, tiffs_header, sizeof tiffs_header)) {
+			fprintf(stderr,
+			"error: block specified with -a has no TIFFS header\n");
+			exit(1);
+		}
+		if (ptr[8] != 0xAB) {
+			fprintf(stderr,
+			"error: block specified with -a is not an AB block\n");
+			exit(1);
+		}
+		inode_block = ptr;
+		return(0);
+	}
+	abcnt = 0;
+	for (ptr = image, i = 0; i < total_blocks; i++, ptr += eraseblk_size) {
+		if (bcmp(ptr, tiffs_header, sizeof tiffs_header)) {
+			fprintf(stderr,
+		"warning: no TIFFS signature in erase block #%d (offset %x)\n",
+				i, ptr - image);
+			continue;
+		}
+		switch (ptr[8]) {
+		case 0xAB:
+			if (verbose)
+				printf(
+			"Found AB index in erase block #%d (offset %x)\n",
+					i, ptr - image);
+			index_blk_num = i;
+			inode_block = ptr;
+			abcnt++;
+			continue;
+		case 0xBD:
+		case 0xBF:
+			continue;
+		}
+		fprintf(stderr,
+		"warning: unexpected block type/status %02X at offset %x\n",
+			ptr[8], ptr - image);
+	}
+	if (!inode_block) {
+		fprintf(stderr,
+			"error: could not find an active inode block in %s\n",
+			imgfile);
+		exit(1);
+	}
+	if (abcnt > 1) {
+		fprintf(stderr,
+			"error: found more than one AB block; use -a\n");
+		exit(1);
+	}
+	return(0);
+}
+
+cmd_fsinfo()
+{
+	read_ffs_image();
+	find_inode_block();
+	printf("Active inode block (AB) is block #%d\n", index_blk_num);
+	exit(0);
+}