Source file src/pkg/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	}

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