internal ref struct BinaryPacket
{
    private int _offset;
    private int _capacity;
    private void GrowSize(int additional)
    {
        while (_offset + additional > _capacity) _capacity *= 2; //_capacity 初始值为 0 时， 0 * 2 = 0 恒成立，条件是死循环。
        _bytesToReturnToPool = ArrayPool<byte>.Shared.Rent(_capacity);

        _span[.._offset].CopyTo(_bytesToReturnToPool.AsSpan());

        _span = _bytesToReturnToPool.AsSpan();
        _buffer = ref Unsafe.Add(ref MemoryMarshal.GetReference(_span), _offset);
    }
}