public ByteBuffer readAll ( ) throws IOException { MappedByteBuffer bb = dataFileChannel . map ( FileChannel . MapMode . READ_ONLY , startOffset , length ) ; return bb ; }
Maps in the relevant portion of the file . This avoid copying the data from OS pages into this process s page . It will be automatically unmapped when the ByteBuffer that is returned here goes out of scope . This method is currently invoked only by the FSDataInputStream ScatterGather api .