New API calls isoburn_ropt_set_displacement(), isoburn_ropt_get_displacement()

libisoburn/isoburn.h

@@ -242,12 +242,15 @@ int isoburn_get_msc2(struct isoburn *o,
 /** Get a data source suitable for read from a drive using burn_read_data()
     function.
     @param d drive to read from. Must be grabbed.
+    @param displacement will be added or subtracted to any block address
+    @param displacement_sign  +1 = add , -1= subtract , else keep unaltered
     @return the data source, NULL on error. Must be freed with libisofs
             iso_data_source_unref() function. Note: this doesn't release
             the drive.
 */
 IsoDataSource *
-isoburn_data_source_new(struct burn_drive *d);
+isoburn_data_source_new(struct burn_drive *d,
+                         uint32_t displacement, int displacement_sign);
 
 /** Disable read capabilities of a data source which was originally created
     by isoburn_data_source_new(). After this any attempt to read will yield
@@ -332,6 +335,9 @@ struct isoburn_read_opts {
     uint32_t size; /**< Will be filled with the size (in 2048 byte block) of 
                     *   the image, as reported in the PVM. */
     unsigned int pretend_blank:1; /* always create empty image */
+
+    uint32_t displacement;
+    int displacement_sign;
 };