Get the total number of bytes in a buffer sequence.

template<
    typename BufferSequence>
std::size_t buffer_size(
    const BufferSequence & b);

The buffer_size function determines the total size of all buffers in the buffer sequence, as if computed as follows:

size_t total_size = 0;
auto i = std::experimental::net::buffer_sequence_begin(buffers);
auto end = std::experimental::net::buffer_sequence_end(buffers);
for (; i != end; ++i)
{
  const_buffer b(*i);
  total_size += b.size();
}
return total_size;

The BufferSequence template parameter may meet either of the ConstBufferSequence or MutableBufferSequence type requirements.