Add logfile.go

src/logfile/logfile.go

@@ -0,0 +1,87 @@
+package logfile
+
+import (
+	"fmt"
+	"os"
+	"time"
+)
+
+type Logfile struct {
+	file *os.File
+	name string
+	nlines int
+	maxlines int
+}
+
+func NewLogfile(maxlines int) (*Logfile) {
+	return &Logfile{nil, "", 0, maxlines}
+}
+
+func (lf *Logfile) Close() {
+	if lf.file != nil {
+		lf.writeln("EXIT")
+		lf.file.Close()
+	}
+}
+
+func (lf *Logfile) writeln(s string) error {
+	_, err := fmt.Fprintf(lf.file, "%d %s\n", time.Now().Unix(), s)
+	if err == nil {
+		lf.nlines += 1
+	}
+	return err
+}
+
+func (lf *Logfile) rotate() error {
+	fn := fmt.Sprintf("%s.log", time.Now().UTC().Format(time.RFC3339))
+	newf, err := os.OpenFile(fn, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0666)
+	if err != nil {
+		return err
+	}
+	
+	if lf.file == nil {
+		// Set lf.file just so we can write out NEXTLOG.
+		// If this fails, that's okay
+		lf.file, _ = os.OpenFile("current", os.O_WRONLY|os.O_APPEND, 0666)
+	}
+	
+	if lf.file != nil {
+		// Note location of new log
+		logmsg := fmt.Sprintf(". NEXTLOG %s", fn)
+		lf.writeln(logmsg)
+		
+		// All done with the current log
+		lf.file.Close()
+	}
+	
+	// Point to new log file
+	lf.file = newf
+		
+	// Record symlink to new log
+	os.Remove("current")
+	os.Symlink(fn, "current")
+	
+	logmsg := fmt.Sprintf(". PREVLOG %s", lf.name)
+	lf.writeln(logmsg)
+	
+	lf.name = fn
+	
+	return nil
+}
+
+func (lf *Logfile) Log(s string) error {
+	if lf.file == nil {
+		lf.rotate()
+	}
+	
+	err := lf.writeln(s)
+	if err == nil {
+		return err
+	}
+
+	if lf.nlines >= lf.maxlines {
+		return lf.rotate()
+	}
+	
+	return nil
+}