Function decrement

3rd/asio-1.24.0/include/asio/buffers_iterator.hpp:377–404

Decrement the iterator.

  // Decrement the iterator.
  void decrement()
  {
    ASIO_ASSERT(position_ > 0 && "iterator out of bounds");
    --position_;

    // Check if the decrement can be satisfied by the current buffer.
    if (current_buffer_position_ != 0)
    {
      --current_buffer_position_;
      return;
    }

    // Find the previous non-empty buffer.
    buffer_sequence_iterator_type iter = current_;
    while (iter != begin_)
    {
      --iter;
      buffer_type buffer = *iter;
      std::size_t buffer_size = buffer.size();
      if (buffer_size > 0)
      {
        current_ = iter;
        current_buffer_ = buffer;
        current_buffer_position_ = buffer_size - 1;
        return;
      }
    }
  }

  // Advance the iterator by the specified distance.
  void advance(std::ptrdiff_t n)