blockIn instanceof FileInputStream) {
FileChannel fileChannel = ((FileInputStream)blockIn).getChannel();
// blockInPosition also indicates sendChunks() uses transferTo.
blockInPosition = fileChannel.position();
streamForSendChunks = baseStream;
// assure a mininum buffer size.
maxChunksPerPacket = (Math.max(BUFFER_SIZE,
MIN_BUFFER_WITH_TRANSFERTO)