protected static void ensureSpace(ByteBuffer out, int length)
    throws EncoderBufferTooSmallException {
    if (out.position() + length > out.limit()) {
      throw new EncoderBufferTooSmallException("Buffer position=" + out.position()
        + ", buffer limit=" + out.limit() + ", length to be written=" + length);
    }
  }
Asserts that there is at least the given amount of unfilled space remaining in the given
buffer.
@param out    typically, the buffer we are writing to
@param length the required space in the buffer
@throws EncoderBufferTooSmallException If there are no enough bytes.
hbase-common/src/main/java/org/apache/hadoop/hbase/io/encoding/BufferedDataBlockEncoder.java