void start_download(curl::multi& multi, const std::string& url)
{
std::auto_ptr<curl::easy> easy(new curl::easy(multi));
// see 'Use server-provided file names' example for a more detailed implementation of this function which receives
// the target file name from the server using libcurl's header callbacks
std::string file_name = url.substr(url.find_last_of('/') + 1);
easy->set_url(url);
easy->set_sink(boost::make_shared<std::ofstream>(file_name.c_str(), std::ios::binary));
easy->async_perform(boost::bind(handle_download_completed, boost::asio::placeholders::error, url, easy.get()));
active_downloads.insert(easy);
}
void insert(boost::ptr_set<T> &arg_ptr_set, ///< The ptr_set into which the value should be inserted
std::unique_ptr<T> &&arg_ptr_value ///< The associated value to insert, held by unique_ptr
) {
arg_ptr_set.insert( arg_ptr_value.release() );
}