Header lib for simplified godbolt logging

godbolt_log.h

/* 
 * File:   Log.h
 * Based on https://stackoverflow.com/a/17605306/ by manu343726
 * https://github.com/Manu343726/Cpp11CustomLogClass
 * Author: xkortex
 * Stackoverflow code snipets are licensed under cc-wiki 
 */

#ifndef LOG_H
#define	LOG_H

#include <iostream>
#include <ctime>
#include <string>

static std::string isonow(void) {
    struct timespec ts;
    timespec_get(&ts, TIME_UTC);
    char buf_sec[32];
    char buf_frac[16];
    // %Y-%m-%d 
    strftime(buf_sec, sizeof(buf_sec), "%H:%M:%S", gmtime(&ts.tv_sec));
    double fracs = ((double) ts.tv_nsec ) / 1e9;
    sprintf(buf_frac, "%0.6lf", fracs);
    return std::string(buf_sec) + std::string(buf_frac).substr(1);
}

class Log
{
private:
    std::ostream& _out_stream;
    bool         _next_is_begin;
    const std::string _spacer;

    
    using endl_type = std::ostream&(std::ostream&); //This is the key: std::endl is a template function, and this is the signature of that function (For std::ostream).
    
public:
    Log(std::ostream& out_stream) : _spacer(""), _out_stream( out_stream ) , _next_is_begin( true ) {}

    Log(const std::string& spacer ="", std::ostream& out_stream = std::cout) : 
    _spacer(spacer), _out_stream( out_stream ) , _next_is_begin( true ) {}
    
    //Overload for std::endl only:
    Log& operator<<(endl_type endl) {
        _next_is_begin = true;
        _out_stream << endl;
        return *this; 
    }
    
    //Overload for anything else:
    template<typename T>           
    Log& operator<< (const T& data) {

        if( _next_is_begin )
            _out_stream << isonow() << ": " << data;
        else
            _out_stream << _spacer << data;

        _next_is_begin = false;
        return *this; 
    }
};


#endif	/* LOG_H */