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log.go
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log.go
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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package log implements a simple logging package. It defines a type, Logger,
// with methods for formatting output. It also has a predefined 'standard'
// Logger accessible through helper functions Print[f|ln], Fatal[f|ln], and
// Panic[f|ln], which are easier to use than creating a Logger manually.
// That logger writes to standard error and prints the date and time
// of each logged message.
package logger
import (
"fmt"
"io"
"os"
"runtime"
"strings"
"sync"
"time"
)
// These constants identify the log levels in order of increasing severity
const (
DEBUG = iota
INFO
WARNING
ERROR
)
// These flags define which text to prefix to each log entry generated by the Logger.
const (
// Bits or'ed together to control what's printed. There is no control over the
// order they appear (the order listed here) or the format they present (as
// described in the comments). A colon appears after these items:
// 2009.01.23 01:23:23.123123 /a/b/c/d.go:23: message
Ldate = 1 << iota // the date: 2009.01.23
Ltime // the time: 01:23:23
Lmicroseconds // microsecond resolution: 01:23:23.123123. assumes Ltime.
Llongfile // full file name and line number: /a/b/c/d.go:23
Lshortfile // final file name element and line number: d.go:23. overrides Llongfile
LstdFlags = Ldate | Ltime // initial values for the standard logger
)
var levelChar = [4]byte{'D', 'I', 'W', 'E'}
// A Logger represents an active logging object that generates lines of
// output to an io.Writer. Each logging operation makes a single call to
// the Writer's Write method. A Logger can be used simultaneously from
// multiple goroutines; it guarantees to serialize access to the Writer.
type Logger struct {
mu sync.Mutex // ensures atomic writes; protects the following fields
prefix string // prefix to write at beginning of each line
flag int // properties
level int // verbosity level
out io.Writer // destination for output
buf []byte // for accumulating text to write
}
// New creates a new Logger. The out variable sets the
// destination to which log data will be written.
// The prefix appears at the beginning of each generated log line.
// The flag argument defines the logging properties.
func New(out io.Writer, prefix string, level int) *Logger {
return &Logger{
out: out,
prefix: prefix,
flag: LstdFlags,
level: level,
}
}
var std = New(os.Stderr, "", DEBUG)
// Cheap integer to fixed-width decimal ASCII. Give a negative width to avoid zero-padding.
func itoa(buf *[]byte, i int, wid int) {
// Assemble decimal in reverse order.
var b [20]byte
bp := len(b) - 1
for i >= 10 || wid > 1 {
wid--
q := i / 10
b[bp] = byte('0' + i - q*10)
bp--
i = q
}
// i < 10
b[bp] = byte('0' + i)
*buf = append(*buf, b[bp:]...)
}
func formatHeader(buf *[]byte, t time.Time,
file, prefix string, line, level, flag int) {
if flag&(Ldate|Ltime|Lmicroseconds) != 0 {
if flag&Ldate != 0 {
year, month, day := t.Date()
itoa(buf, year, 4)
*buf = append(*buf, '.')
itoa(buf, int(month), 2)
*buf = append(*buf, '.')
itoa(buf, day, 2)
*buf = append(*buf, ' ')
}
if flag&(Ltime|Lmicroseconds) != 0 {
hour, min, sec := t.Clock()
itoa(buf, hour, 2)
*buf = append(*buf, ':')
itoa(buf, min, 2)
*buf = append(*buf, ':')
itoa(buf, sec, 2)
if flag&Lmicroseconds != 0 {
*buf = append(*buf, '.')
itoa(buf, t.Nanosecond()/1e3, 6)
}
*buf = append(*buf, ' ')
}
}
if flag&(Lshortfile|Llongfile) != 0 {
if flag&Lshortfile != 0 {
short := file
for i := len(file) - 1; i > 0; i-- {
if file[i] == '/' {
short = file[i+1:]
break
}
}
file = short
}
*buf = append(*buf, file...)
*buf = append(*buf, ':')
itoa(buf, line, -1)
*buf = append(*buf, ": "...)
}
if len(prefix) > 0 {
*buf = append(*buf, prefix...)
*buf = append(*buf, ' ')
}
*buf = append(*buf, '[', levelChar[level], ']', ' ')
}
// Output writes the output for a logging event. The string s contains
// the text to print after the prefix specified by the flags of the
// Logger. A newline is appended if the last character of s is not
// already a newline. Calldepth is used to recover the PC and is
// provided for generality, although at the moment on all pre-defined
// paths it will be 2.
func (l *Logger) Output(calldepth, level int, s string) error {
if level > ERROR || level < 0 {
return fmt.Errorf("Unknown level %d", level)
}
now := time.Now() // get this early
var file string
var line int
l.mu.Lock()
defer l.mu.Unlock()
if l.level > level {
return nil
}
if l.flag&(Lshortfile|Llongfile) != 0 {
// release lock while getting caller info - it's expensive.
l.mu.Unlock()
var ok bool
_, file, line, ok = runtime.Caller(calldepth)
if !ok {
file = "???"
line = 0
}
l.mu.Lock()
}
l.buf = l.buf[:0]
formatHeader(&l.buf, now, file, l.prefix, line, level, l.flag)
l.buf = append(l.buf, s...)
if len(s) > 0 && s[len(s)-1] != '\n' {
l.buf = append(l.buf, '\n')
}
_, err := l.out.Write(l.buf)
return err
}
// Debug calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Print.
func (l *Logger) Debug(v ...interface{}) {
l.Output(2, DEBUG, fmt.Sprint(v...))
}
// Debugf calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Printf.
func (l *Logger) Debugf(format string, v ...interface{}) {
l.Output(2, DEBUG, fmt.Sprintf(format, v...))
}
// Debugln calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Println.
func (l *Logger) Debugln(v ...interface{}) {
l.Output(2, DEBUG, fmt.Sprintln(v...))
}
// Info calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Print.
func (l *Logger) Info(v ...interface{}) {
l.Output(2, INFO, fmt.Sprint(v...))
}
// Infof calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Printf.
func (l *Logger) Infof(format string, v ...interface{}) {
l.Output(2, INFO, fmt.Sprintf(format, v...))
}
// Infoln calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Println.
func (l *Logger) Infoln(v ...interface{}) {
l.Output(2, INFO, fmt.Sprintln(v...))
}
// Warn calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Print.
func (l *Logger) Warn(v ...interface{}) {
l.Output(2, WARNING, fmt.Sprint(v...))
}
// Warnf calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Printf.
func (l *Logger) Warnf(format string, v ...interface{}) {
l.Output(2, WARNING, fmt.Sprintf(format, v...))
}
// Warnln calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Println.
func (l *Logger) Warnln(v ...interface{}) {
l.Output(2, WARNING, fmt.Sprintln(v...))
}
// Error calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Print.
func (l *Logger) Error(v ...interface{}) {
l.Output(2, ERROR, fmt.Sprint(v...))
}
// Errorf calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Printf.
func (l *Logger) Errorf(format string, v ...interface{}) {
l.Output(2, ERROR, fmt.Sprintf(format, v...))
}
// Errorln calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Println.
func (l *Logger) Errorln(v ...interface{}) {
l.Output(2, ERROR, fmt.Sprintln(v...))
}
// Flags returns the output flags for the logger.
func (l *Logger) Flags() int {
l.mu.Lock()
defer l.mu.Unlock()
return l.flag
}
// SetFlags sets the output flags for the logger.
func (l *Logger) SetFlags(flag int) {
l.mu.Lock()
l.flag = flag
l.mu.Unlock()
}
// Prefix returns the output prefix for the logger.
func (l *Logger) Prefix() string {
l.mu.Lock()
defer l.mu.Unlock()
return l.prefix
}
// SetPrefix sets the output prefix for the logger.
func (l *Logger) SetPrefix(prefix string) {
l.mu.Lock()
l.prefix = prefix
l.mu.Unlock()
}
func (l *Logger) Level() int {
l.mu.Lock()
defer l.mu.Unlock()
return l.level
}
func (l *Logger) SetLevel(level int) {
l.mu.Lock()
l.level = level
l.mu.Unlock()
}
func LevelFromString(level string) int {
switch strings.ToUpper(level) {
case "DEBUG":
return DEBUG
case "ERROR":
return ERROR
case "INFO":
return INFO
case "WARNING":
return WARNING
default:
return -1
}
}
func LevelToString(level int) string {
switch level {
case DEBUG:
return "DEBUG"
case ERROR:
return "ERROR"
case INFO:
return "INFO"
case WARNING:
return "WARNING"
default:
return "UNKNOWN"
}
}
// SetOutput sets the output destination for the standard logger.
func SetOutput(w io.Writer) {
std.mu.Lock()
std.out = w
std.mu.Unlock()
}
// Flags returns the output flags for the standard logger.
func Flags() int {
return std.Flags()
}
// SetFlags sets the output flags for the standard logger.
func SetFlags(flag int) {
std.SetFlags(flag)
}
// Prefix returns the output prefix for the standard logger.
func Prefix() string {
return std.Prefix()
}
// SetPrefix sets the output prefix for the standard logger.
func SetPrefix(prefix string) {
std.SetPrefix(prefix)
}
func Level() int {
return std.Level()
}
func SetLevel(level int) {
std.SetLevel(level)
}
// These functions write to the standard logger.
// Debug calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Print.
func Debug(v ...interface{}) {
std.Output(2, DEBUG, fmt.Sprint(v...))
}
// Debugf calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Printf.
func Debugf(format string, v ...interface{}) {
std.Output(2, DEBUG, fmt.Sprintf(format, v...))
}
// Debugln calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Println.
func Debugln(v ...interface{}) {
std.Output(2, DEBUG, fmt.Sprintln(v...))
}
// Info calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Print.
func Info(v ...interface{}) {
std.Output(2, INFO, fmt.Sprint(v...))
}
// Infof calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Printf.
func Infof(format string, v ...interface{}) {
std.Output(2, INFO, fmt.Sprintf(format, v...))
}
// Infoln calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Println.
func Infoln(v ...interface{}) {
std.Output(2, INFO, fmt.Sprintln(v...))
}
// Warn calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Print.
func Warn(v ...interface{}) {
std.Output(2, WARNING, fmt.Sprint(v...))
}
// Warnf calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Printf.
func Warnf(format string, v ...interface{}) {
std.Output(2, WARNING, fmt.Sprintf(format, v...))
}
// Warnln calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Println.
func Warnln(v ...interface{}) {
std.Output(2, WARNING, fmt.Sprintln(v...))
}
// Error calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Print.
func Error(v ...interface{}) {
std.Output(2, ERROR, fmt.Sprint(v...))
}
// Errorf calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Printf.
func Errorf(format string, v ...interface{}) {
std.Output(2, ERROR, fmt.Sprintf(format, v...))
}
// Errorln calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Println.
func Errorln(v ...interface{}) {
std.Output(2, ERROR, fmt.Sprintln(v...))
}