@Override
  public int write(OutputStream out, boolean withTags) throws IOException {
    int length = getSerializedSize(withTags);
    ByteBufferUtils.copyBufferToStream(out, this.buf, this.offset, length);
    return 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