You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: file_storage.go
    path of file: ./repos/ledisdb/vendor/github.com/syndtr/goleveldb/leveldb/storage
    
    the code of the file until where you have to start completion: // Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
// All rights reservefs.
//
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package storage

import (
	"errors"
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"time"
)

var (
	errFileOpen = errors.New("leveldb/storage: file still open")
	errReadOnly = errors.New("leveldb/storage: storage is read-o
    
func (fs *fileStorage) doLog(t time.Time, str string) {
	if fs.logSize > logSizeThreshold {
		// Rotate log file.
		fs.logw.Close()
		fs.logw = nil
		fs.logSize = 0
		rename(filepath.Join(fs.path, "LOG"), filepath.Join(fs.path, "LOG.old"))
	}
	if fs.logw == nil {
		var err error
		fs.logw, err = os.OpenFile(filepath.Join(fs.path, "LOG"), os.O_WRONLY|os.O_CREATE, 0644)
		if err != nil {
			return
		}
		// Force printDay on new log file.
		fs.day = 0
	}
	fs.printDay(t)
	hour, min, sec := t.Clock()
	msec := t.Nanosecond() / 1e3
	// time
	fs.buf = itoa(fs.buf[:0], hour, 2)
	fs.buf = append(fs.buf, ':')
	fs.buf = itoa(fs.buf, min, 2)
	fs.buf = append(fs.buf, ':')
	fs.buf = itoa(fs.buf, sec, 2)
	fs.buf = append(fs.buf, '.')
	fs.buf = itoa(fs.buf, msec, 6)
	fs.buf = append(fs.buf, ' ')
	// write
	fs.buf = append(fs.buf, []byte(str)...)
	fs.buf = append(fs.buf, '\n')
	fs.logw.Write(fs.buf)
}