class LogBuffer
{
public:
    bool is_empty() const { return head_ == tail_; }
    bool is_full()  const { return uint16_t(tail_ + 1) == head_; }
    LogLine& head()       { return log_buffer_[head_]; }
    LogLine& tail()       { return log_buffer_[tail_]; }
    void advance_head()   { ++head_; }
    void advance_hail()   { ++tail_; }
private:
    volatile uint16_t tail_ = 0;     // write position
    LogLine log_buffer_[0xffff + 1]; // relies on the uint16_t overflowing
    volatile uint16_t head_ = 0;     // read position
};