Prefetch more bytes when the ByteBuffer doesn't contain enough bytes for allowing us to recognize the format.
We try to prefetch more bytes only if necessary in order to avoid latency on network connections.


git-svn-id: https://svn.apache.org/repos/asf/sis/branches/JDK7@1510624 13f79535-47bb-0310-9956-ffa450edef68