Source file src/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	// Writer returns the output destination for the standard logger.
   292	func Writer() io.Writer {
   293		return std.Writer()
   294	}
   295	
   296	// These functions write to the standard logger.
   297	
   298	// Print calls Output to print to the standard logger.
   299	// Arguments are handled in the manner of fmt.Print.
   300	func Print(v ...interface{}) {
   301		std.Output(2, fmt.Sprint(v...))
   302	}
   303	
   304	// Printf calls Output to print to the standard logger.
   305	// Arguments are handled in the manner of fmt.Printf.
   306	func Printf(format string, v ...interface{}) {
   307		std.Output(2, fmt.Sprintf(format, v...))
   308	}
   309	
   310	// Println calls Output to print to the standard logger.
   311	// Arguments are handled in the manner of fmt.Println.
   312	func Println(v ...interface{}) {
   313		std.Output(2, fmt.Sprintln(v...))
   314	}
   315	
   316	// Fatal is equivalent to Print() followed by a call to os.Exit(1).
   317	func Fatal(v ...interface{}) {
   318		std.Output(2, fmt.Sprint(v...))
   319		os.Exit(1)
   320	}
   321	
   322	// Fatalf is equivalent to Printf() followed by a call to os.Exit(1).
   323	func Fatalf(format string, v ...interface{}) {
   324		std.Output(2, fmt.Sprintf(format, v...))
   325		os.Exit(1)
   326	}
   327	
   328	// Fatalln is equivalent to Println() followed by a call to os.Exit(1).
   329	func Fatalln(v ...interface{}) {
   330		std.Output(2, fmt.Sprintln(v...))
   331		os.Exit(1)
   332	}
   333	
   334	// Panic is equivalent to Print() followed by a call to panic().
   335	func Panic(v ...interface{}) {
   336		s := fmt.Sprint(v...)
   337		std.Output(2, s)
   338		panic(s)
   339	}
   340	
   341	// Panicf is equivalent to Printf() followed by a call to panic().
   342	func Panicf(format string, v ...interface{}) {
   343		s := fmt.Sprintf(format, v...)
   344		std.Output(2, s)
   345		panic(s)
   346	}
   347	
   348	// Panicln is equivalent to Println() followed by a call to panic().
   349	func Panicln(v ...interface{}) {
   350		s := fmt.Sprintln(v...)
   351		std.Output(2, s)
   352		panic(s)
   353	}
   354	
   355	// Output writes the output for a logging event. The string s contains
   356	// the text to print after the prefix specified by the flags of the
   357	// Logger. A newline is appended if the last character of s is not
   358	// already a newline. Calldepth is the count of the number of
   359	// frames to skip when computing the file name and line number
   360	// if Llongfile or Lshortfile is set; a value of 1 will print the details
   361	// for the caller of Output.
   362	func Output(calldepth int, s string) error {
   363		return std.Output(calldepth+1, s) // +1 for this frame.
   364	}
   365	

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