code: func NewByteBufPool(capacity int, pool Pool) *ByteBuf {
  	return &ByteBuf{
  		capacity:    capacity,
  		buf:         pool.Alloc(capacity),
  		readerIndex: 0,
  		writerIndex: 0,
  		pool:        pool,
  	}
  }
docs: // NewByteBufPool create a new bytebuf using a mem pool