[asio-users] buffers_iterator<detail::consuming_buffers> yields wrong iterator category

[Torsten@Robitzki.de <To...@ro...>]

Hello,
I don't know if this should be considered to be a bug, but it bugs me and maybe others might stumble over it too. I use my own socket class for testing. I implement the AsyncWriteStream type requirments. The problem is, that when I use the passed buffer and construct a buffer_iterator from it's iterator_category is random access, but the resulting iterator doesn't implement the whole category (just read_iterator, if I got it right). Here is a little reproducer, that should generate a compiler error at the "--i" expression:

#include <boost/asio.hpp>
#include <vector>
#include <iterator>

void handler( const boost::system::error_code& error,  std::size_t bytes_transferred);


template <class Iter>
void use_random_access_iterator(Iter i, std::random_access_iterator_tag)
{
	--i;
}

struct socket
{
	template <class CB, class H>
	void async_write_some(const CB& cb, H h)
	{
		typedef boost::asio::buffers_iterator<CB> iter_t;
		use_random_access_iterator(iter_t(), typename std::iterator_traits<iter_t>::iterator_category());
	}
};

void f()
{
	std::vector<boost::asio::const_buffers_1> outbuffer;
	struct socket sock;

	boost::asio::async_write(sock, outbuffer, &handler);
}


Should I fill an error report for this? Can someone see a workaround? I'm not using --i, but insert a sequence into a vector for example, where the stl uses the iterator category.

best regards
Torsten