Introduced checksum tags for superblock and directory tree.

libisofs/md5.h

@@ -26,6 +26,23 @@ int checksum_writer_create(Ecma119Image *target);
 int checksum_xinfo_func(void *data, int flag);
 
 
+/* Write stream detectable checksum tag to extra block.
+ * All tag ranges start at the beginning of the System Area (i.e. t->ms_block)
+ * and stem from the same MD5 computation context. Tag types 2 and 3 are
+ * intermediate checksums. Type 2 announces the existence of type 3.
+ * If both match, then at least the directory tree is trustworthy.
+ * Type 1 is written at the very end of the session. If it matches, then
+ * the whole image is trustworthy.
+ * @param t      The image being written
+ * @param pos    The LBA where this tag block is supposed to be written
+ * @flag         bit0-7= tag type
+ *               1= session tag (End checksumming.)
+ *               2= superblock tag (System Area and Volume Descriptors)
+ *               3= tree tag (ECMA-119 and Rock Ridge tree)
+ */
+int iso_md5_write_tag(Ecma119Image *t, uint32_t pos, int flag);
+
+
 #endif /* ! LIBISO_MD5_H_ */