@Override
  public byte get(int index) {
    checkRefCount();
    if (UNSAFE_AVAIL) {
      return UnsafeAccess.toByte(this.unsafeRef, this.unsafeOffset + index);
    }
    return this.buf.get(index);
  }
An implementation of ByteBuff where a single BB backs the BBI. This just acts as a wrapper over a
normal BB - offheap or onheap
hbase-common/src/main/java/org/apache/hadoop/hbase/nio/SingleByteBuff.java