A constexpr output stream implementation. See tests for example of usage

To create a formatted buffer

daw::static_string_t<char, 100> buffer{}; // Uses a static string, but any contiguous memory area is fine
buffer.resize(buffer.size( )); // makes static string marked as fully used
auto buff_stream = daw::io::make_memory_buffer_stream( buffer.data( ), buffer.size( ) ); // create stream
buff_stream << "The meaning of life is " << 42 << '\n';
buffer.shrink_to_fit( ); // reclaim unused space in buffer

Console output

daw::con_out << "The meaning of life is " << 42 << '\n';

File output

auto fs = daw::make_file_stream( "file_name" );
if( !fs ) {
 daw::con_err << "Error opening file\n";
 exit( EXIT_FAILURE );
}
fs << "The meaining of life is " << 42 << '\n';
fs.close( ); // or let it go out of scope

Add a function to_os_string<CharT>( ClassType ) in your classes namespace that returns a type that is string like(has data( ) and size( )methods). If you want constexpr formatting this function must be constexpr. The provided static_string_t<CharT> can help or a string_view may work too.

Custom streams must provide operator() for character and string like data. They must also specialize daw::io::supports_output_stream_interface<T> to inherit from std::true_type

Otherwise, for composite classes you would overload operator<< like in C++ iostreams. The requirement being that it is a template and uses SFINAE to only allow when daw::io::is_output_stream_v<OutputStream> == true.

Using a format string(or equivilent) of "The asnwer to the meaning of life is %d %f\n" with a double of 42.0

The following are the results:

Tested using strtod/strtof to return string to a double/float