...
Run Format

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	const (
    28		// Bits or'ed together to control what's printed.
    29		// There is no control over the order they appear (the order listed
    30		// here) or the format they present (as described in the comments).
    31		// The prefix is followed by a colon only when Llongfile or Lshortfile
    32		// is specified.
    33		// For example, flags Ldate | Ltime (or LstdFlags) produce,
    34		//	2009/01/23 01:23:23 message
    35		// while flags Ldate | Ltime | Lmicroseconds | Llongfile produce,
    36		//	2009/01/23 01:23:23.123123 /a/b/c/d.go:23: message
    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	func (l *Logger) formatHeader(buf *[]byte, t time.Time, file string, line int) {
    93		*buf = append(*buf, l.prefix...)
    94		if l.flag&LUTC != 0 {
    95			t = t.UTC()
    96		}
    97		if l.flag&(Ldate|Ltime|Lmicroseconds) != 0 {
    98			if l.flag&Ldate != 0 {
    99				year, month, day := t.Date()
   100				itoa(buf, year, 4)
   101				*buf = append(*buf, '/')
   102				itoa(buf, int(month), 2)
   103				*buf = append(*buf, '/')
   104				itoa(buf, day, 2)
   105				*buf = append(*buf, ' ')
   106			}
   107			if l.flag&(Ltime|Lmicroseconds) != 0 {
   108				hour, min, sec := t.Clock()
   109				itoa(buf, hour, 2)
   110				*buf = append(*buf, ':')
   111				itoa(buf, min, 2)
   112				*buf = append(*buf, ':')
   113				itoa(buf, sec, 2)
   114				if l.flag&Lmicroseconds != 0 {
   115					*buf = append(*buf, '.')
   116					itoa(buf, t.Nanosecond()/1e3, 6)
   117				}
   118				*buf = append(*buf, ' ')
   119			}
   120		}
   121		if l.flag&(Lshortfile|Llongfile) != 0 {
   122			if l.flag&Lshortfile != 0 {
   123				short := file
   124				for i := len(file) - 1; i > 0; i-- {
   125					if file[i] == '/' {
   126						short = file[i+1:]
   127						break
   128					}
   129				}
   130				file = short
   131			}
   132			*buf = append(*buf, file...)
   133			*buf = append(*buf, ':')
   134			itoa(buf, line, -1)
   135			*buf = append(*buf, ": "...)
   136		}
   137	}
   138	
   139	// Output writes the output for a logging event. The string s contains
   140	// the text to print after the prefix specified by the flags of the
   141	// Logger. A newline is appended if the last character of s is not
   142	// already a newline. Calldepth is used to recover the PC and is
   143	// provided for generality, although at the moment on all pre-defined
   144	// paths it will be 2.
   145	func (l *Logger) Output(calldepth int, s string) error {
   146		now := time.Now() // get this early.
   147		var file string
   148		var line int
   149		l.mu.Lock()
   150		defer l.mu.Unlock()
   151		if l.flag&(Lshortfile|Llongfile) != 0 {
   152			// release lock while getting caller info - it's expensive.
   153			l.mu.Unlock()
   154			var ok bool
   155			_, file, line, ok = runtime.Caller(calldepth)
   156			if !ok {
   157				file = "???"
   158				line = 0
   159			}
   160			l.mu.Lock()
   161		}
   162		l.buf = l.buf[:0]
   163		l.formatHeader(&l.buf, now, file, line)
   164		l.buf = append(l.buf, s...)
   165		if len(s) == 0 || s[len(s)-1] != '\n' {
   166			l.buf = append(l.buf, '\n')
   167		}
   168		_, err := l.out.Write(l.buf)
   169		return err
   170	}
   171	
   172	// Printf calls l.Output to print to the logger.
   173	// Arguments are handled in the manner of fmt.Printf.
   174	func (l *Logger) Printf(format string, v ...interface{}) {
   175		l.Output(2, fmt.Sprintf(format, v...))
   176	}
   177	
   178	// Print calls l.Output to print to the logger.
   179	// Arguments are handled in the manner of fmt.Print.
   180	func (l *Logger) Print(v ...interface{}) { l.Output(2, fmt.Sprint(v...)) }
   181	
   182	// Println calls l.Output to print to the logger.
   183	// Arguments are handled in the manner of fmt.Println.
   184	func (l *Logger) Println(v ...interface{}) { l.Output(2, fmt.Sprintln(v...)) }
   185	
   186	// Fatal is equivalent to l.Print() followed by a call to os.Exit(1).
   187	func (l *Logger) Fatal(v ...interface{}) {
   188		l.Output(2, fmt.Sprint(v...))
   189		os.Exit(1)
   190	}
   191	
   192	// Fatalf is equivalent to l.Printf() followed by a call to os.Exit(1).
   193	func (l *Logger) Fatalf(format string, v ...interface{}) {
   194		l.Output(2, fmt.Sprintf(format, v...))
   195		os.Exit(1)
   196	}
   197	
   198	// Fatalln is equivalent to l.Println() followed by a call to os.Exit(1).
   199	func (l *Logger) Fatalln(v ...interface{}) {
   200		l.Output(2, fmt.Sprintln(v...))
   201		os.Exit(1)
   202	}
   203	
   204	// Panic is equivalent to l.Print() followed by a call to panic().
   205	func (l *Logger) Panic(v ...interface{}) {
   206		s := fmt.Sprint(v...)
   207		l.Output(2, s)
   208		panic(s)
   209	}
   210	
   211	// Panicf is equivalent to l.Printf() followed by a call to panic().
   212	func (l *Logger) Panicf(format string, v ...interface{}) {
   213		s := fmt.Sprintf(format, v...)
   214		l.Output(2, s)
   215		panic(s)
   216	}
   217	
   218	// Panicln is equivalent to l.Println() followed by a call to panic().
   219	func (l *Logger) Panicln(v ...interface{}) {
   220		s := fmt.Sprintln(v...)
   221		l.Output(2, s)
   222		panic(s)
   223	}
   224	
   225	// Flags returns the output flags for the logger.
   226	func (l *Logger) Flags() int {
   227		l.mu.Lock()
   228		defer l.mu.Unlock()
   229		return l.flag
   230	}
   231	
   232	// SetFlags sets the output flags for the logger.
   233	func (l *Logger) SetFlags(flag int) {
   234		l.mu.Lock()
   235		defer l.mu.Unlock()
   236		l.flag = flag
   237	}
   238	
   239	// Prefix returns the output prefix for the logger.
   240	func (l *Logger) Prefix() string {
   241		l.mu.Lock()
   242		defer l.mu.Unlock()
   243		return l.prefix
   244	}
   245	
   246	// SetPrefix sets the output prefix for the logger.
   247	func (l *Logger) SetPrefix(prefix string) {
   248		l.mu.Lock()
   249		defer l.mu.Unlock()
   250		l.prefix = prefix
   251	}
   252	
   253	// SetOutput sets the output destination for the standard logger.
   254	func SetOutput(w io.Writer) {
   255		std.mu.Lock()
   256		defer std.mu.Unlock()
   257		std.out = w
   258	}
   259	
   260	// Flags returns the output flags for the standard logger.
   261	func Flags() int {
   262		return std.Flags()
   263	}
   264	
   265	// SetFlags sets the output flags for the standard logger.
   266	func SetFlags(flag int) {
   267		std.SetFlags(flag)
   268	}
   269	
   270	// Prefix returns the output prefix for the standard logger.
   271	func Prefix() string {
   272		return std.Prefix()
   273	}
   274	
   275	// SetPrefix sets the output prefix for the standard logger.
   276	func SetPrefix(prefix string) {
   277		std.SetPrefix(prefix)
   278	}
   279	
   280	// These functions write to the standard logger.
   281	
   282	// Print calls Output to print to the standard logger.
   283	// Arguments are handled in the manner of fmt.Print.
   284	func Print(v ...interface{}) {
   285		std.Output(2, fmt.Sprint(v...))
   286	}
   287	
   288	// Printf calls Output to print to the standard logger.
   289	// Arguments are handled in the manner of fmt.Printf.
   290	func Printf(format string, v ...interface{}) {
   291		std.Output(2, fmt.Sprintf(format, v...))
   292	}
   293	
   294	// Println calls Output to print to the standard logger.
   295	// Arguments are handled in the manner of fmt.Println.
   296	func Println(v ...interface{}) {
   297		std.Output(2, fmt.Sprintln(v...))
   298	}
   299	
   300	// Fatal is equivalent to Print() followed by a call to os.Exit(1).
   301	func Fatal(v ...interface{}) {
   302		std.Output(2, fmt.Sprint(v...))
   303		os.Exit(1)
   304	}
   305	
   306	// Fatalf is equivalent to Printf() followed by a call to os.Exit(1).
   307	func Fatalf(format string, v ...interface{}) {
   308		std.Output(2, fmt.Sprintf(format, v...))
   309		os.Exit(1)
   310	}
   311	
   312	// Fatalln is equivalent to Println() followed by a call to os.Exit(1).
   313	func Fatalln(v ...interface{}) {
   314		std.Output(2, fmt.Sprintln(v...))
   315		os.Exit(1)
   316	}
   317	
   318	// Panic is equivalent to Print() followed by a call to panic().
   319	func Panic(v ...interface{}) {
   320		s := fmt.Sprint(v...)
   321		std.Output(2, s)
   322		panic(s)
   323	}
   324	
   325	// Panicf is equivalent to Printf() followed by a call to panic().
   326	func Panicf(format string, v ...interface{}) {
   327		s := fmt.Sprintf(format, v...)
   328		std.Output(2, s)
   329		panic(s)
   330	}
   331	
   332	// Panicln is equivalent to Println() followed by a call to panic().
   333	func Panicln(v ...interface{}) {
   334		s := fmt.Sprintln(v...)
   335		std.Output(2, s)
   336		panic(s)
   337	}
   338	
   339	// Output writes the output for a logging event. The string s contains
   340	// the text to print after the prefix specified by the flags of the
   341	// Logger. A newline is appended if the last character of s is not
   342	// already a newline. Calldepth is the count of the number of
   343	// frames to skip when computing the file name and line number
   344	// if Llongfile or Lshortfile is set; a value of 1 will print the details
   345	// for the caller of Output.
   346	func Output(calldepth int, s string) error {
   347		return std.Output(calldepth+1, s) // +1 for this frame.
   348	}
   349	

View as plain text