transferring bytes from one ByteBuffer to another

Question

What\'s the most efficient way to put as many bytes as possible from a ByteBuffer bbuf_src into another ByteBuffer bbuf_dest (as well as know how m

Answer 1

As you've discovered, getting the backing array doesn't always work (it fails for read only buffers, direct buffers, and memory mapped file buffers). The better alternative is to duplicate your source buffer and set a new limit for the amount of data you want to transfer:

int maxTransfer = Math.min(bbuf_dest.remaining(), bbuf_src.remaining());
// use a duplicated buffer so we don't disrupt the limit of the original buffer
ByteBuffer bbuf_tmp = bbuf_src.duplicate ();
bbuf_tmp.limit (bbuf_tmp.position() + maxTransfer);
bbuf_dest.put (bbuf_tmp);

// now discard the data we've copied from the original source (optional)
bbuf_src.position(bbuf_src.position() + maxTransfer);