base: add new ChunkGenerator method to identify last chunk

src/base/chunk_generator.hh

@@ -122,6 +122,12 @@ class ChunkGenerator
      */
     bool done() const { return (curSize == 0); }
 
+    /**
+     * Is this the last chunk?
+     * @return True if yes, false if more to go.
+     */
+    bool last() const { return (sizeLeft == 0); }
+
     /**
      * Advance generator to next chunk.
      * @return True if successful, false if unsuccessful