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