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authorLuke Shumaker <lukeshu@sbcglobal.net>2016-12-18 03:20:47 -0500
committerLuke Shumaker <lukeshu@sbcglobal.net>2016-12-18 03:20:47 -0500
commit3b1bdfbd2687e81bef85260f9cdfbf617ece3527 (patch)
tree93f2c45e6e616ab63e5fb21f4d2a740d8b9b05e2 /sd_daemon/log.go
parenteb6e8a6ca87879a6ca85788fcf6d3bf8848088e6 (diff)
Implement almost all of sd-daemon. BREAKING CHANGES.v0.2.0
This does not include the sd_is_* utility functions. BREAKING CHANGES: - The import name is now "sd_daemon" instead of "sd". - The logger interface is now entirely different. - Notify now takes more arguments.
Diffstat (limited to 'sd_daemon/log.go')
-rw-r--r--sd_daemon/log.go87
1 files changed, 87 insertions, 0 deletions
diff --git a/sd_daemon/log.go b/sd_daemon/log.go
new file mode 100644
index 0000000..76a735f
--- /dev/null
+++ b/sd_daemon/log.go
@@ -0,0 +1,87 @@
+// Copyright 2015-2016 Luke Shumaker
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:generate make
+
+package sd_daemon
+
+import (
+ "io"
+ "os"
+ "strings"
+ "sync"
+ "fmt"
+ "log/syslog"
+)
+
+// Logger writes "<N>"-prefixed lines to an io.Writer, where N is a
+// syslog priority number. It implements mostly the same interface as
+// "log/syslog".Writer.
+//
+// You probably don't need any instance of this other than the
+// constant "Log", which uses os.Stderr as the writer. It is
+// implemented as a struct rather than a set of functions so that it
+// can be passed around as an implementation of an interface.
+type Logger struct{
+ mu sync.Mutex
+ out io.Writer
+}
+
+func NewLogger(w io.Writer) Logger {
+ return Logger{out: w}
+}
+
+// Log is a Logger that use used very similarly to
+// "log/syslog".Writer, but writes to os.Stderr under the assumption
+// that stderr is forwarded to syslog/journald.
+//
+// You are encouraged to use stderr unless you have a good reason to
+// talk to syslog or journald directly.
+var Log = Logger{out: os.Stderr}
+
+// WriteString writes a message with the specified priority to the
+// log.
+func (l Logger) WriteBytes(level syslog.Priority, msg []byte) (n int, err error) {
+ return l.WriteString(level, string(msg))
+}
+
+// WriteString writes a message with the specified priority to the
+// log.
+func (l Logger) WriteString(level syslog.Priority, msg string) (n int, err error) {
+ l.mu.Lock()
+ defer l.mu.Unlock()
+
+ // BUG(lukeshu): Logger uses high-level string functions that
+ // do many small allocations, making it insuitable for in
+ // tight loops; it should use a buffer property to be
+ // essentially zero-allocation.
+ prefix := fmt.Sprintf("<%d>", level)
+ buf := prefix + strings.Replace(strings.TrimSuffix(msg, "\n"), "\n", "\n"+prefix, -1)
+ return io.WriteString(l.out, buf)
+}
+
+type loggerWriter struct {
+ log Logger
+ level syslog.Priority
+}
+
+func (lw loggerWriter) Write(p []byte) (n int, err error) {
+ return lw.log.WriteBytes(lw.level, p)
+}
+
+// Writer returns an io.Writer that writes messages with the specified
+// priority to the log.
+func (l Logger) Writer(level syslog.Priority) io.Writer {
+ return loggerWriter{log: l, level: level}
+}