log.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package glog implements a simple logging package. It defines a type, Logger,
// with methods for formatting output. It also has a predefined 'standard'
// Logger accessible through helper functions Print[f|ln], Fatal[f|ln], and
// Panic[f|ln], which are easier to use than creating a Logger manually.
// That logger writes to standard error and prints the date and time
// of each logged message.
// Helper functions (Error|Warn|Info|Debug)ln(), (Error|Warn|Info|Debug)f() and
// (Error|Warn|Info|Debug)() writes to log only if it meets the required loglevel (ErrorLevel,
// WarnLevel, InfoLevel, and DebugLevel).
// The Fatal functions call os.Exit(1) after writing the log message.
// The Panic functions call panic after writing the log message.
package glog

import (
	"fmt"
	"io"
	"os"
	"runtime"
	"sync"
	"time"
//	"bytes"
)

// These flags define which text to prefix to each log entry generated by the Logger.
const (
	// Bits or'ed together to control what's printed.
	// There is no control over the order they appear (the order listed
	// here) or the format they present (as described in the comments).
	// The prefix is followed by a colon only when Llongfile or Lshortfile
	// is specified.
	// For example, flags Ldate | Ltime (or LstdFlags) produce,
	//	2009/01/23 01:23:23 message
	// while flags Ldate | Ltime | Lmicroseconds | Llongfile produce,
	//	2009/01/23 01:23:23.123123 /a/b/c/d.go:23: message
	Ldate         = 1 << iota     // the date in the local time zone: 2009/01/23
	Ltime                         // the time in the local time zone: 01:23:23
	Lmicroseconds                 // microsecond resolution: 01:23:23.123123.  assumes Ltime.
	Llongfile                     // full file name and line number: /a/b/c/d.go:23
	Lshortfile                    // final file name element and line number: d.go:23. overrides Llongfile
	LUTC                          // if Ldate or Ltime is set, use UTC rather than the local time zone
	LstdFlags     = Ldate | Ltime // initial values for the standard logger
)

// Constants for defining loglevels
const (
	ErrorLevel uint = iota // 0
	WarnLevel // 1
	InfoLevel // 2
	DebugLevel // 3
)

var l uint = ErrorLevel
// standardLogLevel is the default loglevel checked when calling (Error|Warn|Info|Debug)ln(). This is
// set to ErrorLevel(0) by default.
var standardLogLevel *uint = &l

// SetStandardLogLevel changes the default standardLogLevel variable from ErrorLevel to any of
// (Warn|Info|Debug)Level. This will NOT change the loglevel inside type Logger struct.
func SetStandardLogLevel(loglevel *uint){

	standardLogLevel = loglevel
}

// A Logger represents an active logging object that generates lines of
// output to an io.Writer.  Each logging operation makes a single call to
// the Writer's Write method.  A Logger can be used simultaneously from
// multiple goroutines; it guarantees to serialize access to the Writer.
type Logger struct {
	mu     sync.Mutex // ensures atomic writes; protects the following fields
	prefix string     // prefix to write at beginning of each line
	flag   int        // properties
	out    io.Writer  // destination for output
	buf    []byte     // for accumulating text to write
	loglevel *uint	  // for defining a loglevel for filtering when logging.
}

// SetLogLevel overrides the default loglevel of 0 (ErrorLevel) set by the New() function. 
// This log level is used at runtime to determine if a log has to be printed.
func (l *Logger)SetLogLevel(loglevel *uint) {
	l.loglevel = loglevel
}
// New creates a new Logger.   The out variable sets the
// destination to which log data will be written.
// The prefix appears at the beginning of each generated log line.
// The flag argument defines the logging properties. Log level is
// set as ErrorLevel by default.
func New(out io.Writer, prefix string, flag int) *Logger {
	loglevel := ErrorLevel
	return &Logger{out: out, prefix: prefix, flag: flag, loglevel: &loglevel}
}

// SetOutput sets the output destination for the logger.
func (l *Logger) SetOutput(w io.Writer) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.out = w
}

var std = New(os.Stderr, "", LstdFlags)

// Cheap integer to fixed-width decimal ASCII.  Give a negative width to avoid zero-padding.
func itoa(buf *[]byte, i int, wid int) {
	// Assemble decimal in reverse order.
	var b [20]byte
	bp := len(b) - 1
	for i >= 10 || wid > 1 {
		wid--
		q := i / 10
		b[bp] = byte('0' + i - q*10)
		bp--
		i = q
	}
	// i < 10
	b[bp] = byte('0' + i)
	*buf = append(*buf, b[bp:]...)
}

func (l *Logger) formatHeader(buf *[]byte, t time.Time, file string, line int) {
	*buf = append(*buf, l.prefix...)
	if l.flag&LUTC != 0 {
		t = t.UTC()
	}
	if l.flag&(Ldate|Ltime|Lmicroseconds) != 0 {
		if l.flag&Ldate != 0 {
			year, month, day := t.Date()
			itoa(buf, year, 4)
			*buf = append(*buf, '/')
			itoa(buf, int(month), 2)
			*buf = append(*buf, '/')
			itoa(buf, day, 2)
			*buf = append(*buf, ' ')
		}
		if l.flag&(Ltime|Lmicroseconds) != 0 {
			hour, min, sec := t.Clock()
			itoa(buf, hour, 2)
			*buf = append(*buf, ':')
			itoa(buf, min, 2)
			*buf = append(*buf, ':')
			itoa(buf, sec, 2)
			if l.flag&Lmicroseconds != 0 {
				*buf = append(*buf, '.')
				itoa(buf, t.Nanosecond()/1e3, 6)
			}
			*buf = append(*buf, ' ')
		}
	}
	if l.flag&(Lshortfile|Llongfile) != 0 {
		if l.flag&Lshortfile != 0 {
			short := file
			for i := len(file) - 1; i > 0; i-- {
				if file[i] == '/' {
					short = file[i+1:]
					break
				}
			}
			file = short
		}
		*buf = append(*buf, file...)
		*buf = append(*buf, ':')
		itoa(buf, line, -1)
		*buf = append(*buf, ": "...)
	}
}

// Output writes the output for a logging event.  The string s contains
// the text to print after the prefix specified by the flags of the
// Logger.  A newline is appended if the last character of s is not
// already a newline.  Calldepth is used to recover the PC and is
// provided for generality, although at the moment on all pre-defined
// paths it will be 2.
func (l *Logger) Output(calldepth int, s string) error {
	now := time.Now() // get this early.
	var file string
	var line int
	l.mu.Lock()
	defer l.mu.Unlock()
	if l.flag&(Lshortfile|Llongfile) != 0 {
		// release lock while getting caller info - it's expensive.
		l.mu.Unlock()
		var ok bool
		_, file, line, ok = runtime.Caller(calldepth)
		if !ok {
			file = "???"
			line = 0
		}
		l.mu.Lock()
	}
	l.buf = l.buf[:0]
	l.formatHeader(&l.buf, now, file, line)
	l.buf = append(l.buf, s...)
	if len(s) == 0 || s[len(s)-1] != '\n' {
		l.buf = append(l.buf, '\n')
	}
	_, err := l.out.Write(l.buf)
	return err
}

// Printf calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Printf.
func (l *Logger) Printf(format string, v ...interface{}) {
	l.Output(2, fmt.Sprintf(format, v...))
}

// Errorf calls l.Output to print to the logger only if loglevel >= constant ErrorLevel.
// Arguments are handled in the manner of fmt.Printf.
func (l *Logger) Errorf(format string, v ...interface{}) {
	if *l.loglevel >= ErrorLevel {
		v = append([]interface{}{"ERROR:"}, v...)
		// Adding an extra %s to accommodate the "ERROR:" string.
		// Since it is only one prepend and format is already a string,
		// not using bytes.Buffer to concatenate format string.
		/*
		var buffer bytes.Buffer
		buffer.WriteString("%s ")
		buffer.WriteString(format)
		*/
		l.Output(2, fmt.Sprintf("%s " + format, v...))
	}
}

// Warnf calls l.Output to print to the logger only if loglevel >= constant WarnLevel.
// Arguments are handled in the manner of fmt.Printf.
func (l *Logger) Warnf(format string, v ...interface{}) {
	if *l.loglevel >= WarnLevel {
		v = append([]interface{}{"WARN:"}, v...)
		// Adding an extra %s to accommodate the "WARN:" string.
		l.Output(2, fmt.Sprintf("%s " + format, v...))
	}
}

// Infof calls l.Output to print to the logger only if loglevel >= constant InfoLevel.
// Arguments are handled in the manner of fmt.Printf.
func (l *Logger) Infof(format string, v ...interface{}) {
	if *l.loglevel >= InfoLevel {
		// Adding an extra %s to accommodate the "INFO:" string.
		v = append([]interface{}{"INFO:"}, v...)
		l.Output(2, fmt.Sprintf("%s " + format, v...))
	}
}

// Debugf calls l.Output to print to the logger only if loglevel >= constant DebugLevel.
// Arguments are handled in the manner of fmt.Printf.
func (l *Logger) Debugf(format string, v ...interface{}) {
	if *l.loglevel >= DebugLevel {
		v = append([]interface{}{"DEBUG:"}, v...)
		// Adding an extra %s to accommodate the "DEBUG:" string.
		l.Output(2, fmt.Sprintf("%s " + format, v...))
	}
}

// Print calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Print.
func (l *Logger) Print(v ...interface{}) { l.Output(2, fmt.Sprint(v...)) }

// Error calls l.Output to print to the logger only if loglevel >= constant ErrorLevel.
// Arguments are handled in the manner of fmt.Print.
func (l *Logger) Error(v ...interface{}) {
	if *l.loglevel >= ErrorLevel {
		v = append([]interface{}{"ERROR: "}, v...)
		l.Output(2, fmt.Sprint(v...))
	}
}

// Warn calls l.Output to print to the logger only if loglevel >= constant WarnLevel.
// Arguments are handled in the manner of fmt.Print.
func (l *Logger) Warn(v ...interface{}) {
	if *l.loglevel >= WarnLevel {
		v = append([]interface{}{"WARN: "}, v...)
		l.Output(2, fmt.Sprint(v...))
	}
}

// Info calls l.Output to print to the logger only if loglevel >= constant InfoLevel.
// Arguments are handled in the manner of fmt.Print.
func (l *Logger) Info(v ...interface{}) {
	if *l.loglevel >= InfoLevel {
		v = append([]interface{}{"INFO: "}, v...)
		l.Output(2, fmt.Sprint(v...))
	}
}

// Debug calls l.Output to print to the logger only if loglevel >= constant DebugLevel.
// Arguments are handled in the manner of fmt.Print.
func (l *Logger) Debug(v ...interface{}) {
	if *l.loglevel >= DebugLevel {
		v = append([]interface{}{"DEBUG: "}, v...)
		l.Output(2, fmt.Sprintln(v...))
	}
}


// Println calls l.Output to print to the logger.
// Arguments are handled in the manner of fmt.Println.
func (l *Logger) Println(v ...interface{}) {
	l.Output(2, fmt.Sprintln(v...))
}

// Errorln calls l.Output to print to the logger only if loglevel >= constant ErrorLevel.
// Arguments are handled in the manner of fmt.Println.
func (l *Logger) Errorln(v ...interface{}) {
	if *l.loglevel >= ErrorLevel {
		v = append([]interface{}{"ERROR:"}, v...)
		l.Output(2, fmt.Sprintln(v...))
	}
}

// Warnln calls l.Output to print to the logger only if loglevel >= constant WarnLevel.
// Arguments are handled in the manner of fmt.Println.
func (l *Logger) Warnln(v ...interface{}) {
	if *l.loglevel >= WarnLevel {
		v = append([]interface{}{"WARN:"}, v...)
		l.Output(2, fmt.Sprintln(v...))
	}
}

// Infoln calls l.Output to print to the logger only if loglevel >= constant InfoLevel.
// Arguments are handled in the manner of fmt.Println.
func (l *Logger) Infoln(v ...interface{}) {
	if *l.loglevel >= InfoLevel {
		v = append([]interface{}{"INFO:"}, v...)
		l.Output(2, fmt.Sprintln(v...))
	}
}

// Debugln calls l.Output to print to the logger only if loglevel >= constant DebugLevel.
// Arguments are handled in the manner of fmt.Println.
func (l *Logger) Debugln(v ...interface{}) {
	if *l.loglevel >= DebugLevel {
		v = append([]interface{}{"DEBUG:"}, v...)
		l.Output(2, fmt.Sprintln(v...))
	}
}

// Fatal is equivalent to l.Print() followed by a call to os.Exit(1).
func (l *Logger) Fatal(v ...interface{}) {
	l.Output(2, fmt.Sprint(v...))
	os.Exit(1)
}

// Fatalf is equivalent to l.Printf() followed by a call to os.Exit(1).
func (l *Logger) Fatalf(format string, v ...interface{}) {
	l.Output(2, fmt.Sprintf(format, v...))
	os.Exit(1)
}

// Fatalln is equivalent to l.Println() followed by a call to os.Exit(1).
func (l *Logger) Fatalln(v ...interface{}) {
	l.Output(2, fmt.Sprintln(v...))
	os.Exit(1)
}

// Panic is equivalent to l.Print() followed by a call to panic().
func (l *Logger) Panic(v ...interface{}) {
	s := fmt.Sprint(v...)
	l.Output(2, s)
	panic(s)
}

// Panicf is equivalent to l.Printf() followed by a call to panic().
func (l *Logger) Panicf(format string, v ...interface{}) {
	s := fmt.Sprintf(format, v...)
	l.Output(2, s)
	panic(s)
}

// Panicln is equivalent to l.Println() followed by a call to panic().
func (l *Logger) Panicln(v ...interface{}) {
	s := fmt.Sprintln(v...)
	l.Output(2, s)
	panic(s)
}

// Flags returns the output flags for the logger.
func (l *Logger) Flags() int {
	l.mu.Lock()
	defer l.mu.Unlock()
	return l.flag
}

// SetFlags sets the output flags for the logger.
func (l *Logger) SetFlags(flag int) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.flag = flag
}

// Prefix returns the output prefix for the logger.
func (l *Logger) Prefix() string {
	l.mu.Lock()
	defer l.mu.Unlock()
	return l.prefix
}

// SetPrefix sets the output prefix for the logger.
func (l *Logger) SetPrefix(prefix string) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.prefix = prefix
}

// SetOutput sets the output destination for the standard logger.
func SetOutput(w io.Writer) {
	std.mu.Lock()
	defer std.mu.Unlock()
	std.out = w
}

// Flags returns the output flags for the standard logger.
func Flags() int {
	return std.Flags()
}

// SetFlags sets the output flags for the standard logger.
func SetFlags(flag int) {
	std.SetFlags(flag)
}

// Prefix returns the output prefix for the standard logger.
func Prefix() string {
	return std.Prefix()
}

// SetPrefix sets the output prefix for the standard logger.
func SetPrefix(prefix string) {
	std.SetPrefix(prefix)
}

// These functions write to the standard logger.

// Print calls Output to print to the standard logger.
// Arguments are handled in the manner of fmt.Print.
func Print(v ...interface{}) {
	std.Output(2, fmt.Sprint(v...))
}

// Error calls Output to print to the standard logger only if standardLogLevel >= constant ErrorLevel.
// Arguments are handled in the manner of fmt.Print.
func Error(v ...interface{}) {
	if *standardLogLevel >= ErrorLevel {
		v = append([]interface{}{"ERROR:"}, v...)
		std.Output(2, fmt.Sprint(v...))
	}
}

// Warn calls Output to print to the standard logger only if standardLogLevel >= constant WarnLevel.
// Arguments are handled in the manner of fmt.Print.
func Warn(v ...interface{}) {
	if *standardLogLevel >= WarnLevel {
		v = append([]interface{}{"WARN:"}, v...)
		std.Output(2, fmt.Sprint(v...))
	}
}

// Info calls l.Output to print to the standard logger only if standardLogLevel >= constant InfoLevel.
// Arguments are handled in the manner of fmt.Print.
func Info(v ...interface{}) {
	if *standardLogLevel >= InfoLevel {
		v = append([]interface{}{"INFO:"}, v...)
		std.Output(2, fmt.Sprint(v...))
	}
}

// Debug calls l.Output to print to the standard logger only if standardLogLevel >= constant DebugLevel.
// Arguments are handled in the manner of fmt.Print.
func Debug(v ...interface{}) {
	if *standardLogLevel >= DebugLevel {
		v = append([]interface{}{"DEBUG:"}, v...)
		std.Output(2, fmt.Sprint(v...))	}
}

// Printf calls Output to print to the standard logger.
// Arguments are handled in the manner of fmt.Printf.
func Printf(format string, v ...interface{}) {
	std.Output(2, fmt.Sprintf(format, v...))
}

// Errorf calls Output to print to the standard logger only if standardLogLevel >= constant ErrorLevel.
// Arguments are handled in the manner of fmt.Printf.
func Errorf(format string, v ...interface{}) {
	if *standardLogLevel >= ErrorLevel {
		v = append([]interface{}{"ERROR:"}, v...)
		std.Output(2, fmt.Sprintf("%s " + format, v...))
	}
}

// Warnf calls Output to print to the standard logger only if standardLogLevel >= constant WarnLevel.
// Arguments are handled in the manner of fmt.Printf.
func Warnf(format string, v ...interface{}) {
	if *standardLogLevel >= WarnLevel {
		v = append([]interface{}{"WARN:"}, v...)
		std.Output(2, fmt.Sprintf("%s " + format, v...))
	}
}

// Infof calls l.Output to print to the standard logger only if standardLogLevel >= constant InfoLevel.
// Arguments are handled in the manner of fmt.Printf.
func Infof(format string, v ...interface{}) {
	if *standardLogLevel >= InfoLevel {
		v = append([]interface{}{"INFO:"}, v...)
		std.Output(2, fmt.Sprintf("%s " + format, v...))
	}
}

// Debugf calls l.Output to print to the standard logger only if standardLogLevel >= constant DebugLevel.
// Arguments are handled in the manner of fmt.Printf.
func Debugf(format string, v ...interface{}) {
	if *standardLogLevel >= DebugLevel {
		v = append([]interface{}{"DEBUG:"}, v...)
		std.Output(2, fmt.Sprintf("%s " + format, v...))	}
}

// Println calls Output to print to the standard logger.
// Arguments are handled in the manner of fmt.Println.
func Println(v ...interface{}) {
	std.Output(2, fmt.Sprintln(v...))
}

// Errorln calls Output to print to the standard logger only if standardLogLevel >= constant ErrorLevel.
// Arguments are handled in the manner of fmt.Println.
func Errorln(v ...interface{}) {
	if *standardLogLevel >= ErrorLevel {
		v = append([]interface{}{"ERROR:"}, v...)
		std.Output(2, fmt.Sprintln(v...))
	}
}

// Warnln calls Output to print to the standard logger only if standardLogLevel >= constant WarnLevel.
// Arguments are handled in the manner of fmt.Println.
func Warnln(v ...interface{}) {
	if *standardLogLevel >= WarnLevel {
		v = append([]interface{}{"WARN:"}, v...)
		std.Output(2, fmt.Sprintln(v...))
	}
}

// Infoln calls l.Output to print to the standard logger only if standardLogLevel >= constant InfoLevel.
// Arguments are handled in the manner of fmt.Println.
func Infoln(v ...interface{}) {
	if *standardLogLevel >= InfoLevel {
		v = append([]interface{}{"INFO:"}, v...)
		Output(2, fmt.Sprintln(v...))
	}
}

// Debugln calls l.Output to print to the standard logger only if standardLogLevel >= constant DebugLevel.
// Arguments are handled in the manner of fmt.Println.
func Debugln(v ...interface{}) {
	if *standardLogLevel >= DebugLevel {
		v = append([]interface{}{"DEBUG:"}, v...)
		Output(2, fmt.Sprintln(v...))
	}
}

// Fatal is equivalent to Print() followed by a call to os.Exit(1).
func Fatal(v ...interface{}) {
	std.Output(2, fmt.Sprint(v...))
	os.Exit(1)
}

// Fatalf is equivalent to Printf() followed by a call to os.Exit(1).
func Fatalf(format string, v ...interface{}) {
	std.Output(2, fmt.Sprintf(format, v...))
	os.Exit(1)
}

// Fatalln is equivalent to Println() followed by a call to os.Exit(1).
func Fatalln(v ...interface{}) {
	std.Output(2, fmt.Sprintln(v...))
	os.Exit(1)
}

// Panic is equivalent to Print() followed by a call to panic().
func Panic(v ...interface{}) {
	s := fmt.Sprint(v...)
	std.Output(2, s)
	panic(s)
}

// Panicf is equivalent to Printf() followed by a call to panic().
func Panicf(format string, v ...interface{}) {
	s := fmt.Sprintf(format, v...)
	std.Output(2, s)
	panic(s)
}

// Panicln is equivalent to Println() followed by a call to panic().
func Panicln(v ...interface{}) {
	s := fmt.Sprintln(v...)
	std.Output(2, s)
	panic(s)
}

// Output writes the output for a logging event.  The string s contains
// the text to print after the prefix specified by the flags of the
// Logger.  A newline is appended if the last character of s is not
// already a newline.  Calldepth is the count of the number of
// frames to skip when computing the file name and line number
// if Llongfile or Lshortfile is set; a value of 1 will print the details
// for the caller of Output.
func Output(calldepth int, s string) error {
	return std.Output(calldepth+1, s) // +1 for this frame.
}