log levels can have different writers

log/logger.go

@@ -17,16 +17,34 @@ var once sync.Once
 // Logger is a wrapper for log.Logger and provides
 // methods to enable and disable logging.
 type Logger struct {
-	Out      io.Writer
+	DefaultWriter  io.Writer
+	LoglevelWriter map[Level]io.Writer
 	Loglevel       Level
 	lock           sync.Mutex
 	builder        strings.Builder
 }
 
+func (l *Logger) buildMessage(level Level, args ...interface{}) {
+	l.builder.WriteString(time.Now().Format(time.RFC3339))
+	l.builder.WriteRune('\t')
+	l.builder.WriteString(prefix(level))
+	l.builder.WriteRune('\t')
+	function, line := callers()
+	functionSplitted := strings.SplitAfter(function, "/")
+	function = functionSplitted[len(functionSplitted)-1]
+	l.builder.WriteString(function)
+	l.builder.WriteRune(':')
+	l.builder.WriteString(strconv.Itoa(line))
+	l.builder.WriteRune('\t')
+	l.builder.WriteString(fmt.Sprint(args...))
+	l.builder.WriteRune('\n')
+}
+
 func get() *Logger {
 	once.Do(func() {
 		logger = &Logger{
-			Out:      os.Stderr,
+			DefaultWriter:  os.Stderr,
+			LoglevelWriter: make(map[Level]io.Writer),
 			Loglevel:       INFO,
 			lock:           sync.Mutex{},
 		}
@@ -49,7 +67,16 @@ func Output(out io.Writer) {
 	l := get()
 	l.lock.Lock()
 	defer l.lock.Unlock()
-	l.Out = out
+	l.DefaultWriter = out
+}
+
+//LoglevelOutput defines a special output
+//for a certain log level
+func LoglevelOutput(level Level, out io.Writer) {
+	l := get()
+	l.lock.Lock()
+	defer l.lock.Unlock()
+	l.LoglevelWriter[level] = out
 }
 
 //Debug passes the DEBUG flag and a
@@ -101,21 +128,17 @@ func log(level Level, args ...interface{}) {
 	l := get()
 	l.lock.Lock()
 	defer l.lock.Unlock()
+	defer l.builder.Reset()
 	if level <= l.Loglevel {
-		l.builder.WriteString(time.Now().Format(time.RFC3339))
-		l.builder.WriteRune('\t')
-		l.builder.WriteString(prefix(level))
-		l.builder.WriteRune('\t')
-		function, line := callers()
-		functionSplitted := strings.SplitAfter(function, "/")
-		function = functionSplitted[len(functionSplitted) - 1]
-		l.builder.WriteString(function)
-		l.builder.WriteRune(':')
-		l.builder.WriteString(strconv.Itoa(line))
-		l.builder.WriteRune('\t')
-		l.builder.WriteString(fmt.Sprint(args...))
-		l.builder.WriteRune('\n')
-		_,err := l.Out.Write([]byte(l.builder.String()))
+		l.buildMessage(level, args...)
+		msg := []byte(l.builder.String())
+		writer, ok := l.LoglevelWriter[level]
+		var err error
+		if !ok {
+			_, err = l.DefaultWriter.Write(msg)
+		} else {
+			_, err = writer.Write(msg)
+		}
 		if err != nil {
 			panic(err)
 		}
@@ -124,7 +147,7 @@ func log(level Level, args ...interface{}) {
 
 func callers() (string, int) {
 	pc := make([]uintptr, 15)
-	n := runtime.Callers(4, pc)
+	n := runtime.Callers(5, pc)
 	frames := runtime.CallersFrames(pc[:n])
 	frame, _ := frames.Next()
 	return frame.Function, frame.Line