Function get_append_buffer_unused_tail_length

src/include/buffer.h:1006–1008

    void try_assign_to_mempool(int pool);

    size_t get_append_buffer_unused_tail_length() const {
      return _carriage->unused_tail_length();
    }

    const buffers_t& buffers() const { return _buffers; }
    buffers_t& mut_buffers() { return _buffers; }