template <typename T>
void memvector<T>::resize( size_type n_s ) {
    if ( size() >= n_s ) return;

    data_->resize( n_s * byte_io::byte_lenght<value_type>() + byte_io::byte_lenght<unsigned>() );
    iterator p_end = end();
    byte_io::write<unsigned>( data_->rw_base( 0 ), n_s );
   while ( operator !=<unsigned, unsigned>(p_end, end()) ) {
        *p_end = value_type();
        ++p_end;

    }