...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Peek at the incoming data on the stream.
template< typename Stream, typename MutableBufferSequence> std::size_t peek( impl_type & impl, Stream & next_layer, const MutableBufferSequence & buffers, boost::system::error_code & ec);