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authorLuke Shumaker <lukeshu@sbcglobal.net>2016-12-19 13:45:53 -0500
committerLuke Shumaker <lukeshu@sbcglobal.net>2016-12-19 13:45:53 -0500
commita04b84778871d77e539a675acbff05f7220e2f5e (patch)
tree4b6c54cdf6d6d5b3c3ef084f604615b2dc2b9c47 /sd_daemon/log.go
parent4a3a5525172afd69bc674a2a344065cd9e9a5888 (diff)
Improve documentation.
Diffstat (limited to 'sd_daemon/log.go')
-rw-r--r--sd_daemon/log.go39
1 files changed, 23 insertions, 16 deletions
diff --git a/sd_daemon/log.go b/sd_daemon/log.go
index 9fa62d4..9b23f31 100644
--- a/sd_daemon/log.go
+++ b/sd_daemon/log.go
@@ -25,14 +25,21 @@ import (
"sync"
)
-// Logger writes "<N>"-prefixed lines to an io.Writer, where N is a
+// A 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.
+// 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.
+//
+// Each logging operation makes a single call to the underlying
+// Writer's Write method. A single logging operation may be multiple
+// lines; each line will have the prefix, and they will all be written
+// in the same Write. A Logger can be used simultaneously from
+// multiple goroutines; it guarantees to serialize access to the
+// Writer.
type Logger struct {
mu sync.Mutex
out io.Writer
@@ -44,9 +51,9 @@ 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.
+// Log is a Logger whose interface is very similar to syslog.Writer,
+// but writes to os.Stderr under the assumption that stderr is
+// forwarded to syslog (or journald).
//
// You are encouraged to use stderr unless you have a good reason to
// talk to syslog or journald directly.
@@ -56,7 +63,7 @@ var Log = NewLogger(os.Stderr)
//
// *buf = append(*buf, fmt.Sprintf("<%d>", n)...)
func appendPrefix(buf []byte, n syslog.Priority) []byte {
- var b [22]byte // 21 = ceil(log_10(2^64))+len("<>")
+ var b [22]byte // 22 = ceil(log_10(2^64))+len("<>")
b[len(b)-1] = '>'
i := len(b) - 2
for n >= 10 {
@@ -72,7 +79,7 @@ func appendPrefix(buf []byte, n syslog.Priority) []byte {
// WriteString writes a message with the specified priority to the
// log.
-func (l *Logger) WriteString(level syslog.Priority, msg string) (n int, err error) {
+func (l *Logger) WriteString(pri syslog.Priority, msg string) (n int, err error) {
l.mu.Lock()
defer l.mu.Unlock()
@@ -80,12 +87,12 @@ func (l *Logger) WriteString(level syslog.Priority, msg string) (n int, err erro
// The following is a cheap version of:
//
- // prefix := fmt.Sprintf("<%d>", level)
+ // prefix := fmt.Sprintf("<%d>", pri)
// buf := prefix + strings.Replace(msg, "\n", "\n"+prefix, -1)
// return io.WriteString(l.out, buf)
l.buf = l.buf[:0]
- l.buf = appendPrefix(l.buf, level) // possible allocation
+ l.buf = appendPrefix(l.buf, pri) // possible allocation
prefix := l.buf
nlines := strings.Count(msg, "\n") + 1
n = len(msg) + len(prefix)*nlines + 1
@@ -109,7 +116,7 @@ func (l *Logger) WriteString(level syslog.Priority, msg string) (n int, err erro
// WriteString writes a message with the specified priority to the
// log.
-func (l *Logger) WriteBytes(level syslog.Priority, msg []byte) (n int, err error) {
+func (l *Logger) WriteBytes(pri syslog.Priority, msg []byte) (n int, err error) {
// Copy/pasted from WriteString and
// * `strings.` -> `bytes.`
// * `"\n"` -> `[]byte{'\n'}`
@@ -119,7 +126,7 @@ func (l *Logger) WriteBytes(level syslog.Priority, msg []byte) (n int, err error
msg = bytes.TrimSuffix(msg, []byte{'\n'})
l.buf = l.buf[:0]
- l.buf = appendPrefix(l.buf, level) // possible allocation
+ l.buf = appendPrefix(l.buf, pri) // possible allocation
prefix := l.buf
nlines := bytes.Count(msg, []byte{'\n'}) + 1
n = len(msg) + len(prefix)*nlines + 1
@@ -142,16 +149,16 @@ func (l *Logger) WriteBytes(level syslog.Priority, msg []byte) (n int, err error
}
type loggerWriter struct {
- log *Logger
- level syslog.Priority
+ log *Logger
+ pri syslog.Priority
}
func (lw loggerWriter) Write(p []byte) (n int, err error) {
- return lw.log.WriteBytes(lw.level, p)
+ return lw.log.WriteBytes(lw.pri, 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}
+func (l *Logger) Writer(pri syslog.Priority) io.Writer {
+ return loggerWriter{log: l, pri: pri}
}