metalog

allows logging to stdout or stderr and/or an output file. levels of logging is defined using a custom struct that is passed as a template.

Log Types

metalog supports 3 kinds of logging:

Log

normal logging:

Log(struct::type type, string format, args...)

Timed Log

does not log the message with specific id unless msec milliseconds have passed since the last time it was published. the id is an integer starting from 0 and should be kept as small as possible (but not necessarily consecutive) since it's backed by a vector. it could've been a hash table but a vector is faster.

TimedLog(struct::type type, id, msec, string format, args...)

Unique Log

backed by a hashed set, it's designed to only go through for new state changes.

UniqueLog(type, string format, args)

Basic Usage

the default log struct (deflog) can be used as such. by default the output is set to stdout (i.e. no logfile) & maximum log level set to deflog::VERBOSE

// using Log = MetaLog<deflog> in the main header allows this:
auto& metalog_instance = Log::GetInstance();
metalog_instance.Init(deflog::ERROR, output::out | output::logfile, "/home/hosein/test_log"); // could also be skipped for default settings
metalog_instance.UniqueLog(deflog::ERROR, "the state is %\n", "A"); // prints
metalog_instance.UniqueLog(deflog::ERROR, "the state is %\n", "A"); // nope
metalog_instance.UniqueLog(deflog::ERROR, "the state is %\n", "A"); // nope
metalog_instance.UniqueLog(deflog::ERROR, "the state is %\n", "B"); // prints
metalog_instance.UniqueLog(deflog::ERROR, "the state is %\n", "A"); // nope
for (size_t i = 0; i < 50000000; ++i) {
    metalog_instance.TimedLog(deflog::ERROR, 0, 200, ">>>>>>>>>>>> timed log %\n", i); // prints 5 times/second
    metalog_instance.Log(deflog::ERROR, "<<<<<<<<<<<< normal log %\n", i);             // prints for all iterations
}

Custom Log Structs

struct new_log_struct {
    enum type : int {
        VERBOSE = 0,
        BASIC = 1,
        INTERMEDIATE = 2,
        ADVANCED = 3
    };
    std::string ToString(type tp) {
        switch (tp)
        {
        case VERBOSE:
            return "verbose";
        case BASIC:
            return "basic";
        case INTERMEDIATE:
            return "intermediate";
        case ADVANCED:
            return "advanced";
        }
    }
};
auto& metalog_instance = MetaLog<new_log_struct>::GetInstance();
metalog_instance.Init(new_log_struct::BASIC, output::out | output::logfile, "/home/usr/test_log");
metalog_instance.UniqueLog(new_log_struct::VERBOSE, "the state is %\n", "A");   // log level too low
metalog_instance.UniqueLog(new_log_struct::BASIC, "the state is %\n", "A");     // prints
metalog_instance.UniqueLog(new_log_struct::BASIC, "the state is %\n", "A");     // nope
metalog_instance.UniqueLog(new_log_struct::BASIC, "the state is %\n", "B");     // prints
metalog_instance.UniqueLog(new_log_struct::BASIC, "the state is %\n", "A");     // nope