Function prepare

3rd/asio-1.24.0/include/asio/buffer.hpp:1890–1904

@b DynamicBuffer_v1: Get a list of buffers that represents the output sequence, with the given size. * Ensures that the output sequence can accommodate @c n bytes, resizing the * basic_string object as necessary. * * @returns An object of type @c mutable_buffers_type that satisfies * MutableBufferSequence requirements, representing basic_string memory * at the start of the output se

   * output sequence.
   */
  mutable_buffers_type prepare(std::size_t n)
  {
    if (size() > max_size() || max_size() - size() < n)
    {
      std::length_error ex("dynamic_string_buffer too long");
      asio::detail::throw_exception(ex);
    }

    if (size_ == (std::numeric_limits<std::size_t>::max)())
      size_ = string_.size(); // Enable v1 behaviour.

    string_.resize(size_ + n);

    return asio::buffer(asio::buffer(string_) + size_, n);
  }

  /// @b DynamicBuffer_v1: Move bytes from the output sequence to the input
  /// sequence.