libgo/go/log/log.go

   1 // Copyright 2009 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Package log implements a simple logging package. It defines a type, Logger,
   6 // with methods for formatting output. It also has a predefined 'standard'
   7 // Logger accessible through helper functions Print[f|ln], Fatal[f|ln], and
   8 // Panic[f|ln], which are easier to use than creating a Logger manually.
   9 // That logger writes to standard error and prints the date and time
  10 // of each logged message.
  11 // The Fatal functions call os.Exit(1) after writing the log message.
  12 // The Panic functions call panic after writing the log message.
  13 package log
  14
  15 import (
  16         "fmt"
  17         "io"
  18         "os"
  19         "runtime"
  20         "sync"
  21         "time"
  22 )
  23
  24 // These flags define which text to prefix to each log entry generated by the Logger.
  25 const (
  26         // Bits or'ed together to control what's printed. There is no control over the
  27         // order they appear (the order listed here) or the format they present (as
  28         // described in the comments).  A colon appears after these items:
  29         //      2009/01/23 01:23:23.123123 /a/b/c/d.go:23: message
  30         Ldate         = 1 << iota     // the date: 2009/01/23
  31         Ltime                         // the time: 01:23:23
  32         Lmicroseconds                 // microsecond resolution: 01:23:23.123123.  assumes Ltime.
  33         Llongfile                     // full file name and line number: /a/b/c/d.go:23
  34         Lshortfile                    // final file name element and line number: d.go:23. overrides Llongfile
  35         LstdFlags     = Ldate | Ltime // initial values for the standard logger
  36 )
  37
  38 // A Logger represents an active logging object that generates lines of
  39 // output to an io.Writer.  Each logging operation makes a single call to
  40 // the Writer's Write method.  A Logger can be used simultaneously from
  41 // multiple goroutines; it guarantees to serialize access to the Writer.
  42 type Logger struct {
  43         mu     sync.Mutex // ensures atomic writes; protects the following fields
  44         prefix string     // prefix to write at beginning of each line
  45         flag   int        // properties
  46         out    io.Writer  // destination for output
  47         buf    []byte     // for accumulating text to write
  48 }
  49
  50 // New creates a new Logger.   The out variable sets the
  51 // destination to which log data will be written.
  52 // The prefix appears at the beginning of each generated log line.
  53 // The flag argument defines the logging properties.
  54 func New(out io.Writer, prefix string, flag int) *Logger {
  55         return &Logger{out: out, prefix: prefix, flag: flag}
  56 }
  57
  58 var std = New(os.Stderr, "", LstdFlags)
  59
  60 // Cheap integer to fixed-width decimal ASCII.  Give a negative width to avoid zero-padding.
  61 // Knows the buffer has capacity.
  62 func itoa(buf *[]byte, i int, wid int) {
  63         var u uint = uint(i)
  64         if u == 0 && wid <= 1 {
  65                 *buf = append(*buf, '0')
  66                 return
  67         }
  68
  69         // Assemble decimal in reverse order.
  70         var b [32]byte
  71         bp := len(b)
  72         for ; u > 0 || wid > 0; u /= 10 {
  73                 bp--
  74                 wid--
  75                 b[bp] = byte(u%10) + '0'
  76         }
  77         *buf = append(*buf, b[bp:]...)
  78 }
  79
  80 func (l *Logger) formatHeader(buf *[]byte, t time.Time, file string, line int) {
  81         *buf = append(*buf, l.prefix...)
  82         if l.flag&(Ldate|Ltime|Lmicroseconds) != 0 {
  83                 if l.flag&Ldate != 0 {
  84                         year, month, day := t.Date()
  85                         itoa(buf, year, 4)
  86                         *buf = append(*buf, '/')
  87                         itoa(buf, int(month), 2)
  88                         *buf = append(*buf, '/')
  89                         itoa(buf, day, 2)
  90                         *buf = append(*buf, ' ')
  91                 }
  92                 if l.flag&(Ltime|Lmicroseconds) != 0 {
  93                         hour, min, sec := t.Clock()
  94                         itoa(buf, hour, 2)
  95                         *buf = append(*buf, ':')
  96                         itoa(buf, min, 2)
  97                         *buf = append(*buf, ':')
  98                         itoa(buf, sec, 2)
  99                         if l.flag&Lmicroseconds != 0 {
 100                                 *buf = append(*buf, '.')
 101                                 itoa(buf, t.Nanosecond()/1e3, 6)
 102                         }
 103                         *buf = append(*buf, ' ')
 104                 }
 105         }
 106         if l.flag&(Lshortfile|Llongfile) != 0 {
 107                 if l.flag&Lshortfile != 0 {
 108                         short := file
 109                         for i := len(file) - 1; i > 0; i-- {
 110                                 if file[i] == '/' {
 111                                         short = file[i+1:]
 112                                         break
 113                                 }
 114                         }
 115                         file = short
 116                 }
 117                 *buf = append(*buf, file...)
 118                 *buf = append(*buf, ':')
 119                 itoa(buf, line, -1)
 120                 *buf = append(*buf, ": "...)
 121         }
 122 }
 123
 124 // Output writes the output for a logging event.  The string s contains
 125 // the text to print after the prefix specified by the flags of the
 126 // Logger.  A newline is appended if the last character of s is not
 127 // already a newline.  Calldepth is used to recover the PC and is
 128 // provided for generality, although at the moment on all pre-defined
 129 // paths it will be 2.
 130 func (l *Logger) Output(calldepth int, s string) error {
 131         now := time.Now() // get this early.
 132         var file string
 133         var line int
 134         l.mu.Lock()
 135         defer l.mu.Unlock()
 136         if l.flag&(Lshortfile|Llongfile) != 0 {
 137                 // release lock while getting caller info - it's expensive.
 138                 l.mu.Unlock()
 139                 var ok bool
 140                 _, file, line, ok = runtime.Caller(calldepth)
 141                 if !ok {
 142                         file = "???"
 143                         line = 0
 144                 }
 145                 l.mu.Lock()
 146         }
 147         l.buf = l.buf[:0]
 148         l.formatHeader(&l.buf, now, file, line)
 149         l.buf = append(l.buf, s...)
 150         if len(s) > 0 && s[len(s)-1] != '\n' {
 151                 l.buf = append(l.buf, '\n')
 152         }
 153         _, err := l.out.Write(l.buf)
 154         return err
 155 }
 156
 157 // Printf calls l.Output to print to the logger.
 158 // Arguments are handled in the manner of fmt.Printf.
 159 func (l *Logger) Printf(format string, v ...interface{}) {
 160         l.Output(2, fmt.Sprintf(format, v...))
 161 }
 162
 163 // Print calls l.Output to print to the logger.
 164 // Arguments are handled in the manner of fmt.Print.
 165 func (l *Logger) Print(v ...interface{}) { l.Output(2, fmt.Sprint(v...)) }
 166
 167 // Println calls l.Output to print to the logger.
 168 // Arguments are handled in the manner of fmt.Println.
 169 func (l *Logger) Println(v ...interface{}) { l.Output(2, fmt.Sprintln(v...)) }
 170
 171 // Fatal is equivalent to l.Print() followed by a call to os.Exit(1).
 172 func (l *Logger) Fatal(v ...interface{}) {
 173         l.Output(2, fmt.Sprint(v...))
 174         os.Exit(1)
 175 }
 176
 177 // Fatalf is equivalent to l.Printf() followed by a call to os.Exit(1).
 178 func (l *Logger) Fatalf(format string, v ...interface{}) {
 179         l.Output(2, fmt.Sprintf(format, v...))
 180         os.Exit(1)
 181 }
 182
 183 // Fatalln is equivalent to l.Println() followed by a call to os.Exit(1).
 184 func (l *Logger) Fatalln(v ...interface{}) {
 185         l.Output(2, fmt.Sprintln(v...))
 186         os.Exit(1)
 187 }
 188
 189 // Panic is equivalent to l.Print() followed by a call to panic().
 190 func (l *Logger) Panic(v ...interface{}) {
 191         s := fmt.Sprint(v...)
 192         l.Output(2, s)
 193         panic(s)
 194 }
 195
 196 // Panicf is equivalent to l.Printf() followed by a call to panic().
 197 func (l *Logger) Panicf(format string, v ...interface{}) {
 198         s := fmt.Sprintf(format, v...)
 199         l.Output(2, s)
 200         panic(s)
 201 }
 202
 203 // Panicln is equivalent to l.Println() followed by a call to panic().
 204 func (l *Logger) Panicln(v ...interface{}) {
 205         s := fmt.Sprintln(v...)
 206         l.Output(2, s)
 207         panic(s)
 208 }
 209
 210 // Flags returns the output flags for the logger.
 211 func (l *Logger) Flags() int {
 212         l.mu.Lock()
 213         defer l.mu.Unlock()
 214         return l.flag
 215 }
 216
 217 // SetFlags sets the output flags for the logger.
 218 func (l *Logger) SetFlags(flag int) {
 219         l.mu.Lock()
 220         defer l.mu.Unlock()
 221         l.flag = flag
 222 }
 223
 224 // Prefix returns the output prefix for the logger.
 225 func (l *Logger) Prefix() string {
 226         l.mu.Lock()
 227         defer l.mu.Unlock()
 228         return l.prefix
 229 }
 230
 231 // SetPrefix sets the output prefix for the logger.
 232 func (l *Logger) SetPrefix(prefix string) {
 233         l.mu.Lock()
 234         defer l.mu.Unlock()
 235         l.prefix = prefix
 236 }
 237
 238 // SetOutput sets the output destination for the standard logger.
 239 func SetOutput(w io.Writer) {
 240         std.mu.Lock()
 241         defer std.mu.Unlock()
 242         std.out = w
 243 }
 244
 245 // Flags returns the output flags for the standard logger.
 246 func Flags() int {
 247         return std.Flags()
 248 }
 249
 250 // SetFlags sets the output flags for the standard logger.
 251 func SetFlags(flag int) {
 252         std.SetFlags(flag)
 253 }
 254
 255 // Prefix returns the output prefix for the standard logger.
 256 func Prefix() string {
 257         return std.Prefix()
 258 }
 259
 260 // SetPrefix sets the output prefix for the standard logger.
 261 func SetPrefix(prefix string) {
 262         std.SetPrefix(prefix)
 263 }
 264
 265 // These functions write to the standard logger.
 266
 267 // Print calls Output to print to the standard logger.
 268 // Arguments are handled in the manner of fmt.Print.
 269 func Print(v ...interface{}) {
 270         std.Output(2, fmt.Sprint(v...))
 271 }
 272
 273 // Printf calls Output to print to the standard logger.
 274 // Arguments are handled in the manner of fmt.Printf.
 275 func Printf(format string, v ...interface{}) {
 276         std.Output(2, fmt.Sprintf(format, v...))
 277 }
 278
 279 // Println calls Output to print to the standard logger.
 280 // Arguments are handled in the manner of fmt.Println.
 281 func Println(v ...interface{}) {
 282         std.Output(2, fmt.Sprintln(v...))
 283 }
 284
 285 // Fatal is equivalent to Print() followed by a call to os.Exit(1).
 286 func Fatal(v ...interface{}) {
 287         std.Output(2, fmt.Sprint(v...))
 288         os.Exit(1)
 289 }
 290
 291 // Fatalf is equivalent to Printf() followed by a call to os.Exit(1).
 292 func Fatalf(format string, v ...interface{}) {
 293         std.Output(2, fmt.Sprintf(format, v...))
 294         os.Exit(1)
 295 }
 296
 297 // Fatalln is equivalent to Println() followed by a call to os.Exit(1).
 298 func Fatalln(v ...interface{}) {
 299         std.Output(2, fmt.Sprintln(v...))
 300         os.Exit(1)
 301 }
 302
 303 // Panic is equivalent to Print() followed by a call to panic().
 304 func Panic(v ...interface{}) {
 305         s := fmt.Sprint(v...)
 306         std.Output(2, s)
 307         panic(s)
 308 }
 309
 310 // Panicf is equivalent to Printf() followed by a call to panic().
 311 func Panicf(format string, v ...interface{}) {
 312         s := fmt.Sprintf(format, v...)
 313         std.Output(2, s)
 314         panic(s)
 315 }
 316
 317 // Panicln is equivalent to Println() followed by a call to panic().
 318 func Panicln(v ...interface{}) {
 319         s := fmt.Sprintln(v...)
 320         std.Output(2, s)
 321         panic(s)
 322 }