Minor Description
The method LocalityGroupUtil.encodeColumnFamily(ByteSequence) heeds the current offset and length of the byte sequence, passing them to an private method that does the encoding. However, the private method ignores its offset parameter, and always starts from the beginning of the byte array.
Fortunately, it appears that there are no callers for the public method, and the other caller of the private method always passes an offset of zero. So, the bug is probably not expressed. The method with the bug should probably just be eliminated.