LogForge

LogForge is a no-dependencies logging library for C++. It is designed to be easy to use and easy to extend.

This library can be used completely without inheritance in order to avoid making calls into virtual lookup tables. On the other hand it is also possible to instantiate instances of the corresponding interfaces such as LogOutput, LogFilter, LogPrinter, Logger etc. The example below shows how to use the library without inheritance.

Note that this library is under development. The API may change in the future. This library is inspired by the Dart Logger package.

Filters

Modifier	Description
Development	Filters based on the severity (Debug only)
Production	Filters based on the severity

Outputs

Modifier	Description
Stream	Outputs to a stream
Multi	Outputs to a multiple log outputs

Printers

Modifier	Description	Customizable
Lines	Print only the message without time etc.	No
LogFmt	Print the whole event in logfmt format	Yes
Timestamped	Add a timestamp above the message	Yes
Located	Add a source location above the message	Yes
Boxed	Wrap the message inside a box	No
Prefixed	Adds a prefix based on the Severity	Yes
Colorized	Colorizes the message based on the Severity	Yes

Usage

#include <iostream>
#include <LogForge/LogForge.hpp>

int main() {
	using namespace LogForge;

	// The order matters! Try different orders to see the difference
	const auto printer = Message() //< Could also be LogFmt().
		>> Timestamped()    // Add timestamp to the output
		>> Located()        // Add source location to the output
		>> Boxed()          // Surround the output with a box
		>> Prefixed()       // Add a corresponding prefix to the output
		>> Colorized()      // Add color to the output

	const auto logger = LogForge::DefaultLogger(
		DevelopmentFilter(),
		StreamOutput(std::wcout),
		printer
	);

	logger.Trace(L"This is a trace message");
	logger.Debug(L"This is a debug message");
	logger.Info(L"This is a info message");
	logger.Warning(L"This is a warning message");
	logger.Error(L"This is a error message");
	logger.Fatal(L"This is a fatal message");
}

Using the library would produce outputs like the following:

Additional Information

On Windows, you can use the following code to enable virtual terminal processing in order to see colors etc.:

#include <Windows.h>

BOOL EnableVirtualTerminalProcessing() {
	HANDLE hOut = GetStdHandle(STD_OUTPUT_HANDLE);
	if (hOut == INVALID_HANDLE_VALUE) {
		return FALSE;
	}

	DWORD dwMode = 0;
	if (not GetConsoleMode(hOut, &dwMode)) {
		return FALSE;
	}

	if (not SetConsoleMode(hOut, dwMode | ENABLE_VIRTUAL_TERMINAL_PROCESSING)) {
		return FALSE;
	}

	return TRUE;
}

/// ...

int main() {
	if (not EnableVirtualTerminalProcessing()) {
		std::cerr << "Failed to enable virtual terminal processing" << std::endl;
		return 1;
	)

	// ...
}