Wrap Logger to make disabling output more efficient

Instead of using SetOutput(ioutil.Discard), which means
that Printf is still called for every debug message,
use a simple and fast boolean check.

Streaming write performance improves from 86 to 93 MB/s.

1 files changed, 34 insertions, 8 deletions

diff --git a/cryptfs/log.go b/cryptfs/log.go
index 32fe228..a5b5115 100644
--- a/cryptfs/log.go
+++ b/cryptfs/log.go
@@ -2,8 +2,8 @@ package cryptfs
 
 import (
 	"encoding/json"
-	"io/ioutil"
 	"log"
+	"log/syslog"
 	"os"
 )
 
@@ -16,19 +16,45 @@ func JSONDump(obj interface{}) string {
 	}
 }
 
-// As defined by http://elinux.org/Debugging_by_printing#Log_Levels
+// toggledLogger - a Logger than can be enabled and disabled
+type toggledLogger struct {
+	Enabled bool
+	*log.Logger
+}
+
+func (l *toggledLogger) Printf(format string, v ...interface{}) {
+	if !l.Enabled {
+		return
+	}
+	l.Logger.Printf(format, v...)
+}
+func (l *toggledLogger) Println(v ...interface{}) {
+	if !l.Enabled {
+		return
+	}
+	l.Logger.Println(v...)
+}
+func (l *toggledLogger) SwitchToSyslog(p syslog.Priority) {
+	w, err := syslog.New(p, PROGRAM_NAME)
+	if err != nil {
+		Warn.Printf("Cannot switch 0x%02x to syslog: %v", p, err)
+	} else {
+		l.SetOutput(w)
+	}
+}
 
+// As defined by http://elinux.org/Debugging_by_printing#Log_Levels
 // Debug messages
-var Debug *log.Logger
+var Debug *toggledLogger
 
 // Informational message e.g. startup information
-var Info *log.Logger
+var Info *toggledLogger
 
 // A warning, meaning nothing serious by itself but might indicate problems
-var Warn *log.Logger
+var Warn *toggledLogger
 
 func init() {
-	Debug = log.New(ioutil.Discard, "", 0)
-	Info = log.New(os.Stdout, "", 0)
-	Warn = log.New(os.Stderr, "", 0)
+	Debug = &toggledLogger{false, log.New(os.Stdout, "", 0)}
+	Info = &toggledLogger{true, log.New(os.Stdout, "", 0)}
+	Warn = &toggledLogger{true, log.New(os.Stderr, "", 0)}
 }