Add external logger support

logger.go

@@ -1,6 +1,7 @@
 package cron
 
 import (
+ "io"
  "io/ioutil"
  "log"
  "os"
@@ -56,6 +57,33 @@ func (pl printfLogger) Error(err error, msg string, keysAndValues ...interface{}
  append([]interface{}{msg, "error", err}, keysAndValues...)...)
 }
 
+type externalLogger struct {
+ logger *log.Logger
+}
+
+// NewExternalLogger allows for providing an external logging interface through an io.Writer
+func NewExternalLogger(w io.Writer) *externalLogger {
+ l := log.New(w, "cron: ", log.Llongfile)
+
+ el := externalLogger{
+ logger: l,
+ }
+
+ return &el
+}
+
+func (el *externalLogger) Info(msg string, keysAndValues ...interface{}) {
+ el.logger.Printf(
+ formatString(len(keysAndValues)),
+ append([]interface{}{msg}, keysAndValues...)...)
+}
+
+func (el *externalLogger) Error(err error, msg string, keysAndValues ...interface{}) {
+ el.logger.Printf(
+ formatString(len(keysAndValues)+2),
+ append([]interface{}{msg, "error", err}, keysAndValues...)...)
+}
+
 // formatString returns a logfmt-like format string for the number of
 // key/values.
 func formatString(numKeysAndValues int) string {