@Override
  public void write(ByteBuffer buf, int offset) {
    ByteBufferUtils.copyFromBufferToBuffer(this.buf, buf, this.offset, offset, this.length);
  }
This Cell is an implementation of {@link ByteBufferExtendedCell} where the data resides in off
heap/ on heap ByteBuffer
hbase-common/src/main/java/org/apache/hadoop/hbase/ByteBufferKeyValue.java