Initial implementation of MD5 checksums for session and single data files.

To be activated by macro Libisofs_with_checksumS.
New AAIP attributes "isfs.ca" and "isofs.cx".
New API calls iso_image_get_session_md5() and iso_file_get_md5().

libisofs/image.h

@@ -148,6 +148,22 @@ struct Iso_Image
     uint8_t *used_inodes;
     ino_t used_inodes_start;
 
+#ifdef Libisofs_with_checksumS
+
+    /**
+     * Array of MD5 checksums as announced by xattr "isofs.ca" of the 
+     * root node. Array element 0 contains an overall image checksum for the
+     * block range checksum_start_lba,checksum_end_lba. Element size is
+     * 16 bytes. IsoFile objects in the image may have xattr "isofs.cx"
+     * which gives their index in checksum_array.
+     */
+    uint32_t checksum_start_lba;
+    uint32_t checksum_end_lba;
+    uint32_t checksum_idx_count;
+    char *checksum_array;
+
+#endif /* Libisofs_with_checksumS */
+
 };