glog_formatter.go

// Copyright 2015 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package capnslog

import (
	"bufio"
	"bytes"
	"io"
	"os"
	"runtime"
	"strconv"
	"strings"
	"time"
)

var pid = os.Getpid()

type GlogFormatter struct {
	StringFormatter
}

func NewGlogFormatter(w io.Writer) *GlogFormatter {
	g := &GlogFormatter{}
	g.w = bufio.NewWriter(w)
	return g
}

func (g GlogFormatter) Format(pkg string, level LogLevel, depth int, entries ...interface{}) {
	g.w.Write(GlogHeader(level, depth+1))
	g.StringFormatter.Format(pkg, level, depth+1, entries...)
}

func GlogHeader(level LogLevel, depth int) []byte {
	// Lmmdd hh:mm:ss.uuuuuu threadid file:line]
	now := time.Now().UTC()
	_, file, line, ok := runtime.Caller(depth) // It's always the same number of frames to the user's call.
	if !ok {
		file = "???"
		line = 1
	} else {
		slash := strings.LastIndex(file, "/")
		if slash >= 0 {
			file = file[slash+1:]
		}
	}
	if line < 0 {
		line = 0 // not a real line number
	}
	buf := &bytes.Buffer{}
	buf.Grow(30)
	_, month, day := now.Date()
	hour, minute, second := now.Clock()
	buf.WriteString(level.Char())
	twoDigits(buf, int(month))
	twoDigits(buf, day)
	buf.WriteByte(' ')
	twoDigits(buf, hour)
	buf.WriteByte(':')
	twoDigits(buf, minute)
	buf.WriteByte(':')
	twoDigits(buf, second)
	buf.WriteByte('.')
	buf.WriteString(strconv.Itoa(now.Nanosecond() / 1000))
	buf.WriteByte('Z')
	buf.WriteByte(' ')
	buf.WriteString(strconv.Itoa(pid))
	buf.WriteByte(' ')
	buf.WriteString(file)
	buf.WriteByte(':')
	buf.WriteString(strconv.Itoa(line))
	buf.WriteByte(']')
	buf.WriteByte(' ')
	return buf.Bytes()
}

const digits = "0123456789"

func twoDigits(b *bytes.Buffer, d int) {
	c2 := digits[d%10]
	d /= 10
	c1 := digits[d%10]
	b.WriteByte(c1)
	b.WriteByte(c2)
}