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 // Every log message is output on a separate line: if the message being
  12 // printed does not end in a newline, the logger will add one.
  13 // The Fatal functions call os.Exit(1) after writing the log message.
  14 // The Panic functions call panic after writing the log message.
  15 package log
  16
  17 import (
  18         "fmt"
  19         "io"
  20         "os"
  21         "runtime"
  22         "sync"
  23         "time"
  24 )
  25
  26 // These flags define which text to prefix to each log entry generated by the Logger.
  27 // Bits are or'ed together to control what's printed.
  28 // There is no control over the order they appear (the order listed
  29 // here) or the format they present (as described in the comments).
  30 // The prefix is followed by a colon only when Llongfile or Lshortfile
  31 // is specified.
  32 // For example, flags Ldate | Ltime (or LstdFlags) produce,
  33 //      2009/01/23 01:23:23 message
  34 // while flags Ldate | Ltime | Lmicroseconds | Llongfile produce,
  35 //      2009/01/23 01:23:23.123123 /a/b/c/d.go:23: message
  36 const (
  37         Ldate         = 1 << iota     // the date in the local time zone: 2009/01/23
  38         Ltime                         // the time in the local time zone: 01:23:23
  39         Lmicroseconds                 // microsecond resolution: 01:23:23.123123.  assumes Ltime.
  40         Llongfile                     // full file name and line number: /a/b/c/d.go:23
  41         Lshortfile                    // final file name element and line number: d.go:23. overrides Llongfile
  42         LUTC                          // if Ldate or Ltime is set, use UTC rather than the local time zone
  43         LstdFlags     = Ldate | Ltime // initial values for the standard logger
  44 )
  45
  46 // A Logger represents an active logging object that generates lines of
  47 // output to an io.Writer. Each logging operation makes a single call to
  48 // the Writer's Write method. A Logger can be used simultaneously from
  49 // multiple goroutines; it guarantees to serialize access to the Writer.
  50 type Logger struct {
  51         mu     sync.Mutex // ensures atomic writes; protects the following fields
  52         prefix string     // prefix to write at beginning of each line
  53         flag   int        // properties
  54         out    io.Writer  // destination for output
  55         buf    []byte     // for accumulating text to write
  56 }
  57
  58 // New creates a new Logger. The out variable sets the
  59 // destination to which log data will be written.
  60 // The prefix appears at the beginning of each generated log line.
  61 // The flag argument defines the logging properties.
  62 func New(out io.Writer, prefix string, flag int) *Logger {
  63         return &Logger{out: out, prefix: prefix, flag: flag}
  64 }
  65
  66 // SetOutput sets the output destination for the logger.
  67 func (l *Logger) SetOutput(w io.Writer) {
  68         l.mu.Lock()
  69         defer l.mu.Unlock()
  70         l.out = w
  71 }
  72
  73 var std = New(os.Stderr, "", LstdFlags)
  74
  75 // Cheap integer to fixed-width decimal ASCII. Give a negative width to avoid zero-padding.
  76 func itoa(buf *[]byte, i int, wid int) {
  77         // Assemble decimal in reverse order.
  78         var b [20]byte
  79         bp := len(b) - 1
  80         for i >= 10 || wid > 1 {
  81                 wid--
  82                 q := i / 10
  83                 b[bp] = byte('0' + i - q*10)
  84                 bp--
  85                 i = q
  86         }
  87         // i < 10
  88         b[bp] = byte('0' + i)
  89         *buf = append(*buf, b[bp:]...)
  90 }
  91
  92 // formatHeader writes log header to buf in following order:
  93 //   * l.prefix (if it's not blank),
  94 //   * date and/or time (if corresponding flags are provided),
  95 //   * file and line number (if corresponding flags are provided).
  96 func (l *Logger) formatHeader(buf *[]byte, t time.Time, file string, line int) {
  97         *buf = append(*buf, l.prefix...)
  98         if l.flag&(Ldate|Ltime|Lmicroseconds) != 0 {
  99                 if l.flag&LUTC != 0 {
 100                         t = t.UTC()
 101                 }
 102                 if l.flag&Ldate != 0 {
 103                         year, month, day := t.Date()
 104                         itoa(buf, year, 4)
 105                         *buf = append(*buf, '/')
 106                         itoa(buf, int(month), 2)
 107                         *buf = append(*buf, '/')
 108                         itoa(buf, day, 2)
 109                         *buf = append(*buf, ' ')
 110                 }
 111                 if l.flag&(Ltime|Lmicroseconds) != 0 {
 112                         hour, min, sec := t.Clock()
 113                         itoa(buf, hour, 2)
 114                         *buf = append(*buf, ':')
 115                         itoa(buf, min, 2)
 116                         *buf = append(*buf, ':')
 117                         itoa(buf, sec, 2)
 118                         if l.flag&Lmicroseconds != 0 {
 119                                 *buf = append(*buf, '.')
 120                                 itoa(buf, t.Nanosecond()/1e3, 6)
 121                         }
 122                         *buf = append(*buf, ' ')
 123                 }
 124         }
 125         if l.flag&(Lshortfile|Llongfile) != 0 {
 126                 if l.flag&Lshortfile != 0 {
 127                         short := file
 128                         for i := len(file) - 1; i > 0; i-- {
 129                                 if file[i] == '/' {
 130                                         short = file[i+1:]
 131                                         break
 132                                 }
 133                         }
 134                         file = short
 135                 }
 136                 *buf = append(*buf, file...)
 137                 *buf = append(*buf, ':')
 138                 itoa(buf, line, -1)
 139                 *buf = append(*buf, ": "...)
 140         }
 141 }
 142
 143 // Output writes the output for a logging event. The string s contains
 144 // the text to print after the prefix specified by the flags of the
 145 // Logger. A newline is appended if the last character of s is not
 146 // already a newline. Calldepth is used to recover the PC and is
 147 // provided for generality, although at the moment on all pre-defined
 148 // paths it will be 2.
 149 func (l *Logger) Output(calldepth int, s string) error {
 150         now := time.Now() // get this early.
 151         var file string
 152         var line int
 153         l.mu.Lock()
 154         defer l.mu.Unlock()
 155         if l.flag&(Lshortfile|Llongfile) != 0 {
 156                 // Release lock while getting caller info - it's expensive.
 157                 l.mu.Unlock()
 158                 var ok bool
 159                 _, file, line, ok = runtime.Caller(calldepth)
 160                 if !ok {
 161                         file = "???"
 162                         line = 0
 163                 }
 164                 l.mu.Lock()
 165         }
 166         l.buf = l.buf[:0]
 167         l.formatHeader(&l.buf, now, file, line)
 168         l.buf = append(l.buf, s...)
 169         if len(s) == 0 || s[len(s)-1] != '\n' {
 170                 l.buf = append(l.buf, '\n')
 171         }
 172         _, err := l.out.Write(l.buf)
 173         return err
 174 }
 175
 176 // Printf calls l.Output to print to the logger.
 177 // Arguments are handled in the manner of fmt.Printf.
 178 func (l *Logger) Printf(format string, v ...interface{}) {
 179         l.Output(2, fmt.Sprintf(format, v...))
 180 }
 181
 182 // Print calls l.Output to print to the logger.
 183 // Arguments are handled in the manner of fmt.Print.
 184 func (l *Logger) Print(v ...interface{}) { l.Output(2, fmt.Sprint(v...)) }
 185
 186 // Println calls l.Output to print to the logger.
 187 // Arguments are handled in the manner of fmt.Println.
 188 func (l *Logger) Println(v ...interface{}) { l.Output(2, fmt.Sprintln(v...)) }
 189
 190 // Fatal is equivalent to l.Print() followed by a call to os.Exit(1).
 191 func (l *Logger) Fatal(v ...interface{}) {
 192         l.Output(2, fmt.Sprint(v...))
 193         os.Exit(1)
 194 }
 195
 196 // Fatalf is equivalent to l.Printf() followed by a call to os.Exit(1).
 197 func (l *Logger) Fatalf(format string, v ...interface{}) {
 198         l.Output(2, fmt.Sprintf(format, v...))
 199         os.Exit(1)
 200 }
 201
 202 // Fatalln is equivalent to l.Println() followed by a call to os.Exit(1).
 203 func (l *Logger) Fatalln(v ...interface{}) {
 204         l.Output(2, fmt.Sprintln(v...))
 205         os.Exit(1)
 206 }
 207
 208 // Panic is equivalent to l.Print() followed by a call to panic().
 209 func (l *Logger) Panic(v ...interface{}) {
 210         s := fmt.Sprint(v...)
 211         l.Output(2, s)
 212         panic(s)
 213 }
 214
 215 // Panicf is equivalent to l.Printf() followed by a call to panic().
 216 func (l *Logger) Panicf(format string, v ...interface{}) {
 217         s := fmt.Sprintf(format, v...)
 218         l.Output(2, s)
 219         panic(s)
 220 }
 221
 222 // Panicln is equivalent to l.Println() followed by a call to panic().
 223 func (l *Logger) Panicln(v ...interface{}) {
 224         s := fmt.Sprintln(v...)
 225         l.Output(2, s)
 226         panic(s)
 227 }
 228
 229 // Flags returns the output flags for the logger.
 230 func (l *Logger) Flags() int {
 231         l.mu.Lock()
 232         defer l.mu.Unlock()
 233         return l.flag
 234 }
 235
 236 // SetFlags sets the output flags for the logger.
 237 func (l *Logger) SetFlags(flag int) {
 238         l.mu.Lock()
 239         defer l.mu.Unlock()
 240         l.flag = flag
 241 }
 242
 243 // Prefix returns the output prefix for the logger.
 244 func (l *Logger) Prefix() string {
 245         l.mu.Lock()
 246         defer l.mu.Unlock()
 247         return l.prefix
 248 }
 249
 250 // SetPrefix sets the output prefix for the logger.
 251 func (l *Logger) SetPrefix(prefix string) {
 252         l.mu.Lock()
 253         defer l.mu.Unlock()
 254         l.prefix = prefix
 255 }
 256
 257 // Writer returns the output destination for the logger.
 258 func (l *Logger) Writer() io.Writer {
 259         l.mu.Lock()
 260         defer l.mu.Unlock()
 261         return l.out
 262 }
 263
 264 // SetOutput sets the output destination for the standard logger.
 265 func SetOutput(w io.Writer) {
 266         std.mu.Lock()
 267         defer std.mu.Unlock()
 268         std.out = w
 269 }
 270
 271 // Flags returns the output flags for the standard logger.
 272 func Flags() int {
 273         return std.Flags()
 274 }
 275
 276 // SetFlags sets the output flags for the standard logger.
 277 func SetFlags(flag int) {
 278         std.SetFlags(flag)
 279 }
 280
 281 // Prefix returns the output prefix for the standard logger.
 282 func Prefix() string {
 283         return std.Prefix()
 284 }
 285
 286 // SetPrefix sets the output prefix for the standard logger.
 287 func SetPrefix(prefix string) {
 288         std.SetPrefix(prefix)
 289 }
 290
 291 // These functions write to the standard logger.
 292
 293 // Print calls Output to print to the standard logger.
 294 // Arguments are handled in the manner of fmt.Print.
 295 func Print(v ...interface{}) {
 296         std.Output(2, fmt.Sprint(v...))
 297 }
 298
 299 // Printf calls Output to print to the standard logger.
 300 // Arguments are handled in the manner of fmt.Printf.
 301 func Printf(format string, v ...interface{}) {
 302         std.Output(2, fmt.Sprintf(format, v...))
 303 }
 304
 305 // Println calls Output to print to the standard logger.
 306 // Arguments are handled in the manner of fmt.Println.
 307 func Println(v ...interface{}) {
 308         std.Output(2, fmt.Sprintln(v...))
 309 }
 310
 311 // Fatal is equivalent to Print() followed by a call to os.Exit(1).
 312 func Fatal(v ...interface{}) {
 313         std.Output(2, fmt.Sprint(v...))
 314         os.Exit(1)
 315 }
 316
 317 // Fatalf is equivalent to Printf() followed by a call to os.Exit(1).
 318 func Fatalf(format string, v ...interface{}) {
 319         std.Output(2, fmt.Sprintf(format, v...))
 320         os.Exit(1)
 321 }
 322
 323 // Fatalln is equivalent to Println() followed by a call to os.Exit(1).
 324 func Fatalln(v ...interface{}) {
 325         std.Output(2, fmt.Sprintln(v...))
 326         os.Exit(1)
 327 }
 328
 329 // Panic is equivalent to Print() followed by a call to panic().
 330 func Panic(v ...interface{}) {
 331         s := fmt.Sprint(v...)
 332         std.Output(2, s)
 333         panic(s)
 334 }
 335
 336 // Panicf is equivalent to Printf() followed by a call to panic().
 337 func Panicf(format string, v ...interface{}) {
 338         s := fmt.Sprintf(format, v...)
 339         std.Output(2, s)
 340         panic(s)
 341 }
 342
 343 // Panicln is equivalent to Println() followed by a call to panic().
 344 func Panicln(v ...interface{}) {
 345         s := fmt.Sprintln(v...)
 346         std.Output(2, s)
 347         panic(s)
 348 }
 349
 350 // Output writes the output for a logging event. The string s contains
 351 // the text to print after the prefix specified by the flags of the
 352 // Logger. A newline is appended if the last character of s is not
 353 // already a newline. Calldepth is the count of the number of
 354 // frames to skip when computing the file name and line number
 355 // if Llongfile or Lshortfile is set; a value of 1 will print the details
 356 // for the caller of Output.
 357 func Output(calldepth int, s string) error {
 358         return std.Output(calldepth+1, s) // +1 for this frame.
 359 }