blob: 00bce6a17dc23e6351be5df644862d7e1e330e29 [file] [log] [blame]
// 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.
// The Fatal functions call os.Exit(1) after writing the log message.
// The Panic functions call panic after writing the log message.
package log
import (
"bytes"
"fmt"
"io"
"runtime"
"os"
"time"
"sync"
)
// 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:
// 2009/0123 01:23:23.123123 /a/b/c/d.go:23: message
Ldate = 1 << iota // the date: 2009/0123
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
)
// 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 {
prefix string // prefix to write at beginning of each line
flag int // properties
mu sync.Mutex // ensures atomic writes; protects the following fields
out io.Writer // destination for output
buf bytes.Buffer // 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, flag int) *Logger {
return &Logger{out: out, prefix: prefix, flag: flag}
}
var std = New(os.Stderr, "", LstdFlags)
// Cheap integer to fixed-width decimal ASCII. Give a negative width to avoid zero-padding.
// Knows the buffer has capacity.
func itoa(buf *bytes.Buffer, i int, wid int) {
var u uint = uint(i)
if u == 0 && wid <= 1 {
buf.WriteByte('0')
return
}
// Assemble decimal in reverse order.
var b [32]byte
bp := len(b)
for ; u > 0 || wid > 0; u /= 10 {
bp--
wid--
b[bp] = byte(u%10) + '0'
}
// avoid slicing b to avoid an allocation.
for bp < len(b) {
buf.WriteByte(b[bp])
bp++
}
}
func (l *Logger) formatHeader(buf *bytes.Buffer, ns int64, file string, line int) {
buf.WriteString(l.prefix)
if l.flag&(Ldate|Ltime|Lmicroseconds) != 0 {
t := time.SecondsToLocalTime(ns / 1e9)
if l.flag&Ldate != 0 {
itoa(buf, int(t.Year), 4)
buf.WriteByte('/')
itoa(buf, int(t.Month), 2)
buf.WriteByte('/')
itoa(buf, int(t.Day), 2)
buf.WriteByte(' ')
}
if l.flag&(Ltime|Lmicroseconds) != 0 {
itoa(buf, int(t.Hour), 2)
buf.WriteByte(':')
itoa(buf, int(t.Minute), 2)
buf.WriteByte(':')
itoa(buf, int(t.Second), 2)
if l.flag&Lmicroseconds != 0 {
buf.WriteByte('.')
itoa(buf, int(ns%1e9)/1e3, 6)
}
buf.WriteByte(' ')
}
}
if l.flag&(Lshortfile|Llongfile) != 0 {
if l.flag&Lshortfile != 0 {
short := file
for i := len(file) - 1; i > 0; i-- {
if file[i] == '/' {
short = file[i+1:]
break
}
}
file = short
}
buf.WriteString(file)
buf.WriteByte(':')
itoa(buf, line, -1)
buf.WriteString(": ")
}
}
// 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 int, s string) os.Error {
now := time.Nanoseconds() // get this early.
// get caller info (if required) before locking - it's expensive.
var file string
var line int
if l.flag&(Lshortfile|Llongfile) != 0 {
var ok bool
_, file, line, ok = runtime.Caller(calldepth)
if !ok {
file = "???"
line = 0
}
}
l.mu.Lock()
defer l.mu.Unlock()
l.buf.Reset()
l.formatHeader(&l.buf, now, file, line)
l.buf.WriteString(s)
if len(s) > 0 && s[len(s)-1] != '\n' {
l.buf.WriteByte('\n')
}
_, err := l.out.Write(l.buf.Bytes())
return err
}
// Printf calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Printf.
func (l *Logger) Printf(format string, v ...interface{}) {
l.Output(2, fmt.Sprintf(format, v...))
}
// Print calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Print.
func (l *Logger) Print(v ...interface{}) { l.Output(2, fmt.Sprint(v...)) }
// Println calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Println.
func (l *Logger) Println(v ...interface{}) { l.Output(2, fmt.Sprintln(v...)) }
// Fatal is equivalent to l.Print() followed by a call to os.Exit(1).
func (l *Logger) Fatal(v ...interface{}) {
l.Output(2, fmt.Sprint(v...))
os.Exit(1)
}
// Fatalf is equivalent to l.Printf() followed by a call to os.Exit(1).
func (l *Logger) Fatalf(format string, v ...interface{}) {
l.Output(2, fmt.Sprintf(format, v...))
os.Exit(1)
}
// Fatalln is equivalent to l.Println() followed by a call to os.Exit(1).
func (l *Logger) Fatalln(v ...interface{}) {
l.Output(2, fmt.Sprintln(v...))
os.Exit(1)
}
// Panic is equivalent to l.Print() followed by a call to panic().
func (l *Logger) Panic(v ...interface{}) {
s := fmt.Sprint(v...)
l.Output(2, s)
panic(s)
}
// Panicf is equivalent to l.Printf() followed by a call to panic().
func (l *Logger) Panicf(format string, v ...interface{}) {
s := fmt.Sprintf(format, v...)
l.Output(2, s)
panic(s)
}
// Panicln is equivalent to l.Println() followed by a call to panic().
func (l *Logger) Panicln(v ...interface{}) {
s := fmt.Sprintln(v...)
l.Output(2, s)
panic(s)
}
// Flags returns the output flags for the logger.
func (l *Logger) Flags() int {
return l.flag
}
// SetFlags sets the output flags for the logger.
func (l *Logger) SetFlags(flag int) {
l.flag = flag
}
// Prefix returns the output prefix for the logger.
func (l *Logger) Prefix() string {
return l.prefix
}
// SetPrefix sets the output prefix for the logger.
func (l *Logger) SetPrefix(prefix string) {
l.prefix = prefix
}
// SetOutput sets the output destination for the standard logger.
func SetOutput(w io.Writer) {
std.out = w
}
// 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)
}
// These functions write to the standard logger.
// Print calls Output to print to the standard logger.
// Arguments are handled in the manner of fmt.Print.
func Print(v ...interface{}) {
std.Output(2, fmt.Sprint(v...))
}
// Printf calls Output to print to the standard logger.
// Arguments are handled in the manner of fmt.Printf.
func Printf(format string, v ...interface{}) {
std.Output(2, fmt.Sprintf(format, v...))
}
// Println calls Output to print to the standard logger.
// Arguments are handled in the manner of fmt.Println.
func Println(v ...interface{}) {
std.Output(2, fmt.Sprintln(v...))
}
// Fatal is equivalent to Print() followed by a call to os.Exit(1).
func Fatal(v ...interface{}) {
std.Output(2, fmt.Sprint(v...))
os.Exit(1)
}
// Fatalf is equivalent to Printf() followed by a call to os.Exit(1).
func Fatalf(format string, v ...interface{}) {
std.Output(2, fmt.Sprintf(format, v...))
os.Exit(1)
}
// Fatalln is equivalent to Println() followed by a call to os.Exit(1).
func Fatalln(v ...interface{}) {
std.Output(2, fmt.Sprintln(v...))
os.Exit(1)
}
// Panic is equivalent to Print() followed by a call to panic().
func Panic(v ...interface{}) {
s := fmt.Sprint(v...)
std.Output(2, s)
panic(s)
}
// Panicf is equivalent to Printf() followed by a call to panic().
func Panicf(format string, v ...interface{}) {
s := fmt.Sprintf(format, v...)
std.Output(2, s)
panic(s)
}
// Panicln is equivalent to Println() followed by a call to panic().
func Panicln(v ...interface{}) {
s := fmt.Sprintln(v...)
std.Output(2, s)
panic(s)
}