question: protected synchronized int currentchunkoffset ( ) throws IOException { long fp = backingRandomAccessFile . getFilePointer ( ) ; if ( fp < fHeader . headerSize ( ) ) { return - 1 ; } else { fp -= fHeader . headerSize ( ) ; if ( fp == 0 ) { return 0 ; } else { return ( int ) ( ( fp % CHUNK_ENC_SIZE ) - CHUNK_IV_SIZE ) ; } } }
target:  indicates to which data offset within the current chunk the file pointer currently points