// cleanConfigDirectory removes old, unused configuration and index formats, a
// suitable time after they have gone out of fashion.
func cleanConfigDirectory() {
	patterns := map[string]time.Duration{
		"panic-*.log":    7 * 24 * time.Hour,  // keep panic logs for a week
		"audit-*.log":    7 * 24 * time.Hour,  // keep audit logs for a week
		"index":          14 * 24 * time.Hour, // keep old index format for two weeks
		"config.xml.v*":  30 * 24 * time.Hour, // old config versions for a month
		"*.idx.gz":       30 * 24 * time.Hour, // these should for sure no longer exist
		"backup-of-v0.8": 30 * 24 * time.Hour, // these neither
	}

	for pat, dur := range patterns {
		pat = filepath.Join(baseDirs["config"], pat)
		files, err := osutil.Glob(pat)
		if err != nil {
			l.Infoln("Cleaning:", err)
			continue
		}

		for _, file := range files {
			info, err := osutil.Lstat(file)
			if err != nil {
				l.Infoln("Cleaning:", err)
				continue
			}

			if time.Since(info.ModTime()) > dur {
				if err = os.RemoveAll(file); err != nil {
					l.Infoln("Cleaning:", err)
				} else {
					l.Infoln("Cleaned away old file", filepath.Base(file))
				}
			}
		}
	}
}

func init() {
	defer func() {
		if err := recover(); err != nil {
			// Ensure that the supported flag is disabled when we hit an
			// error, even though it should already be. Also, silently swallow
			// the error since it's fine for a system not to support symlinks.
			Supported = false
		}
	}()

	// Needs administrator privileges.
	// Let's check that everything works.
	// This could be done more officially:
	// http://stackoverflow.com/questions/2094663/determine-if-windows-process-has-privilege-to-create-symbolic-link
	// But I don't want to define 10 more structs just to look this up.
	base := os.TempDir()
	path := filepath.Join(base, "symlinktest")
	defer os.Remove(path)

	err := Create(path, base, protocol.FlagDirectory)
	if err != nil {
		return
	}

	stat, err := osutil.Lstat(path)
	if err != nil || stat.Mode()&os.ModeSymlink == 0 {
		return
	}

	target, flags, err := Read(path)
	if err != nil || osutil.NativeFilename(target) != base || flags&protocol.FlagDirectory == 0 {
		return
	}
	Supported = true
}

// Archive moves the named file away to a version archive. If this function
// returns nil, the named file does not exist any more (has been archived).
func (v External) Archive(filePath string) error {
	_, err := osutil.Lstat(filePath)
	if os.IsNotExist(err) {
		if debug {
			l.Debugln("not archiving nonexistent file", filePath)
		}
		return nil
	} else if err != nil {
		return err
	}

	if debug {
		l.Debugln("archiving", filePath)
	}

	inFolderPath, err := filepath.Rel(v.folderPath, filePath)
	if err != nil {
		return err
	}

	if v.command == "" {
		return errors.New("Versioner: command is empty, please enter a valid command")
	}

	cmd := exec.Command(v.command, v.folderPath, inFolderPath)
	env := os.Environ()
	// filter STGUIAUTH and STGUIAPIKEY from environment variables
	filteredEnv := []string{}
	for _, x := range env {
		if !strings.HasPrefix(x, "STGUIAUTH=") && !strings.HasPrefix(x, "STGUIAPIKEY=") {
			filteredEnv = append(filteredEnv, x)
		}
	}
	cmd.Env = filteredEnv
	err = cmd.Run()
	if err != nil {
		return err
	}

	// return error if the file was not removed
	if _, err = osutil.Lstat(filePath); os.IsNotExist(err) {
		return nil
	}
	return errors.New("Versioner: file was not removed by external script")
}

func checkDir(dir string) error {
	if info, err := osutil.Lstat(dir); err != nil {
		return err
	} else if !info.IsDir() {
		return errors.New(dir + ": not a directory")
	} else if debug {
		l.Debugln("checkDir", dir, info)
	}
	return nil
}

// Archive moves the named file away to a version archive. If this function
// returns nil, the named file does not exist any more (has been archived).
func (t *Trashcan) Archive(filePath string) error {
	_, err := osutil.Lstat(filePath)
	if os.IsNotExist(err) {
		if debug {
			l.Debugln("not archiving nonexistent file", filePath)
		}
		return nil
	} else if err != nil {
		return err
	}

	versionsDir := filepath.Join(t.folderPath, ".stversions")
	if _, err := os.Stat(versionsDir); err != nil {
		if !os.IsNotExist(err) {
			return err
		}

		if debug {
			l.Debugln("creating versions dir", versionsDir)
		}
		if err := osutil.MkdirAll(versionsDir, 0777); err != nil {
			return err
		}
		osutil.HideFile(versionsDir)
	}

	if debug {
		l.Debugln("archiving", filePath)
	}

	relativePath, err := filepath.Rel(t.folderPath, filePath)
	if err != nil {
		return err
	}

	archivedPath := filepath.Join(versionsDir, relativePath)
	if err := osutil.MkdirAll(filepath.Dir(archivedPath), 0777); err != nil && !os.IsExist(err) {
		return err
	}

	if debug {
		l.Debugln("moving to", archivedPath)
	}

	if err := osutil.Rename(filePath, archivedPath); err != nil {
		return err
	}

	// Set the mtime to the time the file was deleted. This is used by the
	// cleanout routine. If this fails things won't work optimally but there's
	// not much we can do about it so we ignore the error.
	os.Chtimes(archivedPath, time.Now(), time.Now())

	return nil
}

func (t *Trashcan) cleanoutArchive() error {
	versionsDir := filepath.Join(t.folderPath, ".stversions")
	if _, err := osutil.Lstat(versionsDir); os.IsNotExist(err) {
		return nil
	}

	cutoff := time.Now().Add(time.Duration(-24*t.cleanoutDays) * time.Hour)
	currentDir := ""
	filesInDir := 0
	walkFn := func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if info.IsDir() {
			// We have entered a new directory. Lets check if the previous
			// directory was empty and try to remove it. We ignore failure for
			// the time being.
			if currentDir != "" && filesInDir == 0 {
				osutil.Remove(currentDir)
			}
			currentDir = path
			filesInDir = 0
			return nil
		}

		if info.ModTime().Before(cutoff) {
			// The file is too old; remove it.
			osutil.Remove(path)
		} else {
			// Keep this file, and remember it so we don't unnecessarily try
			// to remove this directory.
			filesInDir++
		}
		return nil
	}

	if err := filepath.Walk(versionsDir, walkFn); err != nil {
		return err
	}

	// The last directory seen by the walkFn may not have been removed as it
	// should be.
	if currentDir != "" && filesInDir == 0 {
		osutil.Remove(currentDir)
	}
	return nil
}

//.........这里部分代码省略.........
			}
			m.updateLocals(folder, batch)
			batch = batch[:0]
			blocksHandled = 0
		}
		batch = append(batch, f)
		blocksHandled += len(f.Blocks)
	}

	if err := m.CheckFolderHealth(folder); err != nil {
		l.Infof("Stopping folder %s mid-scan due to folder error: %s", folder, err)
		return err
	} else if len(batch) > 0 {
		m.updateLocals(folder, batch)
	}

	batch = batch[:0]
	// TODO: We should limit the Have scanning to start at sub
	seenPrefix := false
	var iterError error
	fs.WithHaveTruncated(protocol.LocalDeviceID, func(fi db.FileIntf) bool {
		f := fi.(db.FileInfoTruncated)
		hasPrefix := len(subs) == 0
		for _, sub := range subs {
			if strings.HasPrefix(f.Name, sub) {
				hasPrefix = true
				break
			}
		}
		// Return true so that we keep iterating, until we get to the part
		// of the tree we are interested in. Then return false so we stop
		// iterating when we've passed the end of the subtree.
		if !hasPrefix {
			return !seenPrefix
		}

		seenPrefix = true
		if !f.IsDeleted() {
			if f.IsInvalid() {
				return true
			}

			if len(batch) == batchSizeFiles {
				if err := m.CheckFolderHealth(folder); err != nil {
					iterError = err
					return false
				}
				m.updateLocals(folder, batch)
				batch = batch[:0]
			}

			if ignores.Match(f.Name) || symlinkInvalid(folder, f) {
				// File has been ignored or an unsupported symlink. Set invalid bit.
				if debug {
					l.Debugln("setting invalid bit on ignored", f)
				}
				nf := protocol.FileInfo{
					Name:     f.Name,
					Flags:    f.Flags | protocol.FlagInvalid,
					Modified: f.Modified,
					Version:  f.Version, // The file is still the same, so don't bump version
				}
				batch = append(batch, nf)
			} else if _, err := osutil.Lstat(filepath.Join(folderCfg.Path(), f.Name)); err != nil {
				// File has been deleted.

				// We don't specifically verify that the error is
				// os.IsNotExist because there is a corner case when a
				// directory is suddenly transformed into a file. When that
				// happens, files that were in the directory (that is now a
				// file) are deleted but will return a confusing error ("not a
				// directory") when we try to Lstat() them.

				nf := protocol.FileInfo{
					Name:     f.Name,
					Flags:    f.Flags | protocol.FlagDeleted,
					Modified: f.Modified,
					Version:  f.Version.Update(m.shortID),
				}
				batch = append(batch, nf)
			}
		}
		return true
	})

	if iterError != nil {
		l.Infof("Stopping folder %s mid-scan due to folder error: %s", folder, iterError)
		return iterError
	}

	if err := m.CheckFolderHealth(folder); err != nil {
		l.Infof("Stopping folder %s mid-scan due to folder error: %s", folder, err)
		return err
	} else if len(batch) > 0 {
		m.updateLocals(folder, batch)
	}

	runner.setState(FolderIdle)
	return nil
}

// Archive moves the named file away to a version archive. If this function
// returns nil, the named file does not exist any more (has been archived).
func (v Simple) Archive(filePath string) error {
	fileInfo, err := osutil.Lstat(filePath)
	if os.IsNotExist(err) {
		if debug {
			l.Debugln("not archiving nonexistent file", filePath)
		}
		return nil
	} else if err != nil {
		return err
	}

	versionsDir := filepath.Join(v.folderPath, ".stversions")
	_, err = os.Stat(versionsDir)
	if err != nil {
		if os.IsNotExist(err) {
			if debug {
				l.Debugln("creating versions dir", versionsDir)
			}
			osutil.MkdirAll(versionsDir, 0755)
			osutil.HideFile(versionsDir)
		} else {
			return err
		}
	}

	if debug {
		l.Debugln("archiving", filePath)
	}

	file := filepath.Base(filePath)
	inFolderPath, err := filepath.Rel(v.folderPath, filepath.Dir(filePath))
	if err != nil {
		return err
	}

	dir := filepath.Join(versionsDir, inFolderPath)
	err = osutil.MkdirAll(dir, 0755)
	if err != nil && !os.IsExist(err) {
		return err
	}

	ver := taggedFilename(file, fileInfo.ModTime().Format(TimeFormat))
	dst := filepath.Join(dir, ver)
	if debug {
		l.Debugln("moving to", dst)
	}
	err = osutil.Rename(filePath, dst)
	if err != nil {
		return err
	}

	// Glob according to the new file~timestamp.ext pattern.
	newVersions, err := osutil.Glob(filepath.Join(dir, taggedFilename(file, TimeGlob)))
	if err != nil {
		l.Warnln("globbing:", err)
		return nil
	}

	// Also according to the old file.ext~timestamp pattern.
	oldVersions, err := osutil.Glob(filepath.Join(dir, file+"~"+TimeGlob))
	if err != nil {
		l.Warnln("globbing:", err)
		return nil
	}

	// Use all the found filenames. "~" sorts after "." so all old pattern
	// files will be deleted before any new, which is as it should be.
	versions := uniqueSortedStrings(append(oldVersions, newVersions...))

	if len(versions) > v.keep {
		for _, toRemove := range versions[:len(versions)-v.keep] {
			if debug {
				l.Debugln("cleaning out", toRemove)
			}
			err = os.Remove(toRemove)
			if err != nil {
				l.Warnln("removing old version:", err)
			}
		}
	}

	return nil
}

// Archive moves the named file away to a version archive. If this function
// returns nil, the named file does not exist any more (has been archived).
func (v Staggered) Archive(filePath string) error {
	if debug {
		l.Debugln("Waiting for lock on ", v.versionsPath)
	}
	v.mutex.Lock()
	defer v.mutex.Unlock()

	_, err := osutil.Lstat(filePath)
	if os.IsNotExist(err) {
		if debug {
			l.Debugln("not archiving nonexistent file", filePath)
		}
		return nil
	} else if err != nil {
		return err
	}

	if _, err := os.Stat(v.versionsPath); err != nil {
		if os.IsNotExist(err) {
			if debug {
				l.Debugln("creating versions dir", v.versionsPath)
			}
			osutil.MkdirAll(v.versionsPath, 0755)
			osutil.HideFile(v.versionsPath)
		} else {
			return err
		}
	}

	if debug {
		l.Debugln("archiving", filePath)
	}

	file := filepath.Base(filePath)
	inFolderPath, err := filepath.Rel(v.folderPath, filepath.Dir(filePath))
	if err != nil {
		return err
	}

	dir := filepath.Join(v.versionsPath, inFolderPath)
	err = osutil.MkdirAll(dir, 0755)
	if err != nil && !os.IsExist(err) {
		return err
	}

	ver := taggedFilename(file, time.Now().Format(TimeFormat))
	dst := filepath.Join(dir, ver)
	if debug {
		l.Debugln("moving to", dst)
	}
	err = osutil.Rename(filePath, dst)
	if err != nil {
		return err
	}

	// Glob according to the new file~timestamp.ext pattern.
	newVersions, err := osutil.Glob(filepath.Join(dir, taggedFilename(file, TimeGlob)))
	if err != nil {
		l.Warnln("globbing:", err)
		return nil
	}

	// Also according to the old file.ext~timestamp pattern.
	oldVersions, err := osutil.Glob(filepath.Join(dir, file+"~"+TimeGlob))
	if err != nil {
		l.Warnln("globbing:", err)
		return nil
	}

	// Use all the found filenames.
	versions := append(oldVersions, newVersions...)
	v.expire(uniqueSortedStrings(versions))

	return nil
}

func (v Staggered) expire(versions []string) {
	if debug {
		l.Debugln("Versioner: Expiring versions", versions)
	}
	var prevAge int64
	firstFile := true
	for _, file := range versions {
		fi, err := osutil.Lstat(file)
		if err != nil {
			l.Warnln("versioner:", err)
			continue
		}

		if fi.IsDir() {
			l.Infof("non-file %q is named like a file version", file)
			continue
		}

		versionTime, err := time.Parse(TimeFormat, filenameTag(file))
		if err != nil {
			if debug {
				l.Debugf("Versioner: file name %q is invalid: %v", file, err)
			}
			continue
		}
		age := int64(time.Since(versionTime).Seconds())

		// If the file is older than the max age of the last interval, remove it
		if lastIntv := v.interval[len(v.interval)-1]; lastIntv.end > 0 && age > lastIntv.end {
			if debug {
				l.Debugln("Versioner: File over maximum age -> delete ", file)
			}
			err = os.Remove(file)
			if err != nil {
				l.Warnf("Versioner: can't remove %q: %v", file, err)
			}
			continue
		}

		// If it's the first (oldest) file in the list we can skip the interval checks
		if firstFile {
			prevAge = age
			firstFile = false
			continue
		}

		// Find the interval the file fits in
		var usedInterval Interval
		for _, usedInterval = range v.interval {
			if age < usedInterval.end {
				break
			}
		}

		if prevAge-age < usedInterval.step {
			if debug {
				l.Debugln("too many files in step -> delete", file)
			}
			err = os.Remove(file)
			if err != nil {
				l.Warnf("Versioner: can't remove %q: %v", file, err)
			}
			continue
		}

		prevAge = age
	}
}

// handleDir creates or updates the given directory
func (p *rwFolder) handleDir(file protocol.FileInfo) {
	var err error
	events.Default.Log(events.ItemStarted, map[string]string{
		"folder": p.folder,
		"item":   file.Name,
		"type":   "dir",
		"action": "update",
	})

	defer func() {
		events.Default.Log(events.ItemFinished, map[string]interface{}{
			"folder": p.folder,
			"item":   file.Name,
			"error":  events.Error(err),
			"type":   "dir",
			"action": "update",
		})
	}()

	realName := filepath.Join(p.dir, file.Name)
	mode := os.FileMode(file.Flags & 0777)
	if p.ignorePermissions(file) {
		mode = 0777
	}

	if debug {
		curFile, _ := p.model.CurrentFolderFile(p.folder, file.Name)
		l.Debugf("need dir\n\t%v\n\t%v", file, curFile)
	}

	info, err := osutil.Lstat(realName)
	switch {
	// There is already something under that name, but it's a file/link.
	// Most likely a file/link is getting replaced with a directory.
	// Remove the file/link and fall through to directory creation.
	case err == nil && (!info.IsDir() || info.Mode()&os.ModeSymlink != 0):
		err = osutil.InWritableDir(osutil.Remove, realName)
		if err != nil {
			l.Infof("Puller (folder %q, dir %q): %v", p.folder, file.Name, err)
			p.newError(file.Name, err)
			return
		}
		fallthrough
	// The directory doesn't exist, so we create it with the right
	// mode bits from the start.
	case err != nil && os.IsNotExist(err):
		// We declare a function that acts on only the path name, so
		// we can pass it to InWritableDir. We use a regular Mkdir and
		// not MkdirAll because the parent should already exist.
		mkdir := func(path string) error {
			err = os.Mkdir(path, mode)
			if err != nil || p.ignorePermissions(file) {
				return err
			}

			// Stat the directory so we can check its permissions.
			info, err := osutil.Lstat(path)
			if err != nil {
				return err
			}

			// Mask for the bits we want to preserve and add them in to the
			// directories permissions.
			return os.Chmod(path, mode|(info.Mode()&retainBits))
		}

		if err = osutil.InWritableDir(mkdir, realName); err == nil {
			p.dbUpdates <- dbUpdateJob{file, dbUpdateHandleDir}
		} else {
			l.Infof("Puller (folder %q, dir %q): %v", p.folder, file.Name, err)
			p.newError(file.Name, err)
		}
		return
	// Weird error when stat()'ing the dir. Probably won't work to do
	// anything else with it if we can't even stat() it.
	case err != nil:
		l.Infof("Puller (folder %q, dir %q): %v", p.folder, file.Name, err)
		p.newError(file.Name, err)
		return
	}

	// The directory already exists, so we just correct the mode bits. (We
	// don't handle modification times on directories, because that sucks...)
	// It's OK to change mode bits on stuff within non-writable directories.
	if p.ignorePermissions(file) {
		p.dbUpdates <- dbUpdateJob{file, dbUpdateHandleDir}
	} else if err := os.Chmod(realName, mode|(info.Mode()&retainBits)); err == nil {
		p.dbUpdates <- dbUpdateJob{file, dbUpdateHandleDir}
	} else {
		l.Infof("Puller (folder %q, dir %q): %v", p.folder, file.Name, err)
		p.newError(file.Name, err)
	}
}

func (p *rwFolder) performFinish(state *sharedPullerState) error {
	// Set the correct permission bits on the new file
	if !p.ignorePermissions(state.file) {
		if err := os.Chmod(state.tempName, os.FileMode(state.file.Flags&0777)); err != nil {
			return err
		}
	}

	// Set the correct timestamp on the new file
	t := time.Unix(state.file.Modified, 0)
	if err := os.Chtimes(state.tempName, t, t); err != nil {
		// Try using virtual mtimes instead
		info, err := os.Stat(state.tempName)
		if err != nil {
			return err
		}
		p.virtualMtimeRepo.UpdateMtime(state.file.Name, info.ModTime(), t)
	}

	var err error
	if p.inConflict(state.version, state.file.Version) {
		// The new file has been changed in conflict with the existing one. We
		// should file it away as a conflict instead of just removing or
		// archiving. Also merge with the version vector we had, to indicate
		// we have resolved the conflict.
		state.file.Version = state.file.Version.Merge(state.version)
		err = osutil.InWritableDir(moveForConflict, state.realName)
	} else if p.versioner != nil {
		// If we should use versioning, let the versioner archive the old
		// file before we replace it. Archiving a non-existent file is not
		// an error.
		err = p.versioner.Archive(state.realName)
	} else {
		err = nil
	}
	if err != nil {
		return err
	}

	// If the target path is a symlink or a directory, we cannot copy
	// over it, hence remove it before proceeding.
	stat, err := osutil.Lstat(state.realName)
	if err == nil && (stat.IsDir() || stat.Mode()&os.ModeSymlink != 0) {
		osutil.InWritableDir(osutil.Remove, state.realName)
	}
	// Replace the original content with the new one
	if err = osutil.Rename(state.tempName, state.realName); err != nil {
		return err
	}

	// If it's a symlink, the target of the symlink is inside the file.
	if state.file.IsSymlink() {
		content, err := ioutil.ReadFile(state.realName)
		if err != nil {
			return err
		}

		// Remove the file, and replace it with a symlink.
		err = osutil.InWritableDir(func(path string) error {
			os.Remove(path)
			return symlinks.Create(path, string(content), state.file.Flags)
		}, state.realName)
		if err != nil {
			return err
		}
	}

	// Record the updated file in the index
	p.dbUpdates <- dbUpdateJob{state.file, dbUpdateHandleFile}
	return nil
}

func (w *Walker) walkAndHashFiles(fchan chan protocol.FileInfo) filepath.WalkFunc {
	now := time.Now()
	return func(p string, info os.FileInfo, err error) error {
		// Return value used when we are returning early and don't want to
		// process the item. For directories, this means do-not-descend.
		var skip error // nil
		// info nil when error is not nil
		if info != nil && info.IsDir() {
			skip = filepath.SkipDir
		}

		if err != nil {
			if debug {
				l.Debugln("error:", p, info, err)
			}
			return skip
		}

		rn, err := filepath.Rel(w.Dir, p)
		if err != nil {
			if debug {
				l.Debugln("rel error:", p, err)
			}
			return skip
		}

		if rn == "." {
			return nil
		}

		mtime := info.ModTime()
		if w.MtimeRepo != nil {
			mtime = w.MtimeRepo.GetMtime(rn, mtime)
		}

		if w.TempNamer != nil && w.TempNamer.IsTemporary(rn) {
			// A temporary file
			if debug {
				l.Debugln("temporary:", rn)
			}
			if info.Mode().IsRegular() && mtime.Add(w.TempLifetime).Before(now) {
				os.Remove(p)
				if debug {
					l.Debugln("removing temporary:", rn, mtime)
				}
			}
			return nil
		}

		if sn := filepath.Base(rn); sn == ".stignore" || sn == ".stfolder" ||
			strings.HasPrefix(rn, ".stversions") || w.Matcher.Match(rn) {
			// An ignored file
			if debug {
				l.Debugln("ignored:", rn)
			}
			return skip
		}

		if !utf8.ValidString(rn) {
			l.Warnf("File name %q is not in UTF8 encoding; skipping.", rn)
			return skip
		}

		var normalizedRn string
		if runtime.GOOS == "darwin" {
			// Mac OS X file names should always be NFD normalized.
			normalizedRn = norm.NFD.String(rn)
		} else {
			// Every other OS in the known universe uses NFC or just plain
			// doesn't bother to define an encoding. In our case *we* do care,
			// so we enforce NFC regardless.
			normalizedRn = norm.NFC.String(rn)
		}

		if rn != normalizedRn {
			// The file name was not normalized.

			if !w.AutoNormalize {
				// We're not authorized to do anything about it, so complain and skip.

				l.Warnf("File name %q is not in the correct UTF8 normalization form; skipping.", rn)
				return skip
			}

			// We will attempt to normalize it.
			normalizedPath := filepath.Join(w.Dir, normalizedRn)
			if _, err := osutil.Lstat(normalizedPath); os.IsNotExist(err) {
				// Nothing exists with the normalized filename. Good.
				if err = os.Rename(p, normalizedPath); err != nil {
					l.Infof(`Error normalizing UTF8 encoding of file "%s": %v`, rn, err)
					return skip
				}
				l.Infof(`Normalized UTF8 encoding of file name "%s".`, rn)
			} else {
				// There is something already in the way at the normalized
				// file name.
				l.Infof(`File "%s" has UTF8 encoding conflict with another file; ignoring.`, rn)
				return skip
			}

//.........这里部分代码省略.........