func dump(ldb *db.Instance) {
	it := ldb.NewIterator(nil, nil)
	for it.Next() {
		key := it.Key()
		switch key[0] {
		case db.KeyTypeDevice:
			folder := binary.BigEndian.Uint32(key[1:])
			device := binary.BigEndian.Uint32(key[1+4:])
			name := nulString(key[1+4+4:])
			fmt.Printf("[device] F:%d D:%d N:%q", folder, device, name)

			var f protocol.FileInfo
			err := f.Unmarshal(it.Value())
			if err != nil {
				log.Fatal(err)
			}
			fmt.Printf(" V:%v\n", f)

		case db.KeyTypeGlobal:
			folder := binary.BigEndian.Uint32(key[1:])
			name := nulString(key[1+4:])
			var flv db.VersionList
			flv.Unmarshal(it.Value())
			fmt.Printf("[global] F:%d N:%q V:%s\n", folder, name, flv)

		case db.KeyTypeBlock:
			folder := binary.BigEndian.Uint32(key[1:])
			hash := key[1+4 : 1+4+32]
			name := nulString(key[1+4+32:])
			fmt.Printf("[block] F:%d H:%x N:%q I:%d\n", folder, hash, name, binary.BigEndian.Uint32(it.Value()))

		case db.KeyTypeDeviceStatistic:
			fmt.Printf("[dstat] K:%x V:%x\n", it.Key(), it.Value())

		case db.KeyTypeFolderStatistic:
			fmt.Printf("[fstat] K:%x V:%x\n", it.Key(), it.Value())

		case db.KeyTypeVirtualMtime:
			fmt.Printf("[mtime] K:%x V:%x\n", it.Key(), it.Value())

		case db.KeyTypeFolderIdx:
			key := binary.BigEndian.Uint32(it.Key()[1:])
			fmt.Printf("[folderidx] K:%d V:%q\n", key, it.Value())

		case db.KeyTypeDeviceIdx:
			key := binary.BigEndian.Uint32(it.Key()[1:])
			val := it.Value()
			if len(val) == 0 {
				fmt.Printf("[deviceidx] K:%d V:<nil>\n", key)
			} else {
				dev := protocol.DeviceIDFromBytes(val)
				fmt.Printf("[deviceidx] K:%d V:%s\n", key, dev)
			}

		default:
			fmt.Printf("[???]\n  %x\n  %x\n", it.Key(), it.Value())
		}
	}
}

func main() {
	log.SetFlags(0)
	log.SetOutput(os.Stdout)

	flag.Parse()

	ldb, err := leveldb.OpenFile(flag.Arg(0), &opt.Options{
		ErrorIfMissing:         true,
		Strict:                 opt.StrictAll,
		OpenFilesCacheCapacity: 100,
	})
	if err != nil {
		log.Fatal(err)
	}

	it := ldb.NewIterator(nil, nil)
	var dev protocol.DeviceID
	for it.Next() {
		key := it.Key()
		switch key[0] {
		case db.KeyTypeDevice:
			folder := nulString(key[1 : 1+64])
			devBytes := key[1+64 : 1+64+32]
			name := nulString(key[1+64+32:])
			copy(dev[:], devBytes)
			fmt.Printf("[device] F:%q N:%q D:%v\n", folder, name, dev)

			var f protocol.FileInfo
			err := f.UnmarshalXDR(it.Value())
			if err != nil {
				log.Fatal(err)
			}
			fmt.Printf("  N:%q\n  F:%#o\n  M:%d\n  V:%v\n  S:%d\n  B:%d\n", f.Name, f.Flags, f.Modified, f.Version, f.Size(), len(f.Blocks))

		case db.KeyTypeGlobal:
			folder := nulString(key[1 : 1+64])
			name := nulString(key[1+64:])
			fmt.Printf("[global] F:%q N:%q V:%x\n", folder, name, it.Value())

		case db.KeyTypeBlock:
			folder := nulString(key[1 : 1+64])
			hash := key[1+64 : 1+64+32]
			name := nulString(key[1+64+32:])
			fmt.Printf("[block] F:%q H:%x N:%q I:%d\n", folder, hash, name, binary.BigEndian.Uint32(it.Value()))

		case db.KeyTypeDeviceStatistic:
			fmt.Printf("[dstat]\n  %x\n  %x\n", it.Key(), it.Value())

		case db.KeyTypeFolderStatistic:
			fmt.Printf("[fstat]\n  %x\n  %x\n", it.Key(), it.Value())

		default:
			fmt.Printf("[???]\n  %x\n  %x\n", it.Key(), it.Value())
		}
	}
}

func unmarshalTrunc(bs []byte, truncate bool) (FileIntf, error) {
	if truncate {
		var tf FileInfoTruncated
		err := tf.UnmarshalXDR(bs)
		return tf, err
	}

	var tf protocol.FileInfo
	err := tf.UnmarshalXDR(bs)
	return tf, err
}

// shortcutSymlink changes the symlinks type if necessary.
func (p *rwFolder) shortcutSymlink(file protocol.FileInfo) (err error) {
	tt := symlinks.TargetFile
	if file.IsDirectory() {
		tt = symlinks.TargetDirectory
	}
	err = symlinks.ChangeType(filepath.Join(p.dir, file.Name), tt)
	if err != nil {
		l.Infof("Puller (folder %q, file %q): symlink shortcut: %v", p.folder, file.Name, err)
		p.newError(file.Name, err)
	}
	return
}

func (t readWriteTransaction) insertFile(folder, device []byte, file protocol.FileInfo) int64 {
	l.Debugf("insert; folder=%q device=%v %v", folder, protocol.DeviceIDFromBytes(device), file)

	if file.LocalVersion == 0 {
		file.LocalVersion = clock(0)
	}

	name := []byte(file.Name)
	nk := deviceKey(folder, device, name)
	t.Put(nk, file.MustMarshalXDR())

	return file.LocalVersion
}

func ldbInsert(batch dbWriter, folder, device []byte, file protocol.FileInfo) int64 {
	l.Debugf("insert; folder=%q device=%v %v", folder, protocol.DeviceIDFromBytes(device), file)

	if file.LocalVersion == 0 {
		file.LocalVersion = clock(0)
	}

	name := []byte(file.Name)
	nk := deviceKey(folder, device, name)
	l.Debugf("batch.Put %p %x", batch, nk)
	batch.Put(nk, file.MustMarshalXDR())

	return file.LocalVersion
}

// requires write lock on model.fmut before entry
// requires file does not exist in local model
func (m *Model) addToLocalModel(deviceID protocol.DeviceID, folder string, file protocol.FileInfo) {
	if file.IsDeleted() {
		if debug {
			l.Debugln("peer", deviceID.String(), "has deleted file, doing nothing", file.Name)
		}
		return
	}
	if file.IsInvalid() {
		if debug {
			l.Debugln("peer", deviceID.String(), "has invalid file, doing nothing", file.Name)
		}
		return
	}
	if file.IsSymlink() {
		if debug {
			l.Debugln("peer", deviceID.String(), "has symlink, doing nothing", file.Name)
		}
		return
	}

	if debug && file.IsDirectory() {
		l.Debugln("peer", deviceID.String(), "has directory, adding", file.Name)
	} else if debug {
		l.Debugln("peer", deviceID.String(), "has file, adding", file.Name)
	}

	m.treeCaches[folder].AddEntry(file)

	m.addPeerForEntry(deviceID, folder, file)
}

// Test that updating a file removes it's old blocks from the blockmap
func TestCopierCleanup(t *testing.T) {
	iterFn := func(folder, file string, index int32) bool {
		return true
	}

	db, _ := leveldb.Open(storage.NewMemStorage(), nil)
	m := NewModel(defaultConfig, protocol.LocalDeviceID, "device", "syncthing", "dev", db)
	m.AddFolder(defaultFolderConfig)

	// Create a file
	file := protocol.FileInfo{
		Name:     "test",
		Flags:    0,
		Modified: 0,
		Blocks:   []protocol.BlockInfo{blocks[0]},
	}

	// Add file to index
	m.updateLocals("default", []protocol.FileInfo{file})

	if !m.finder.Iterate(folders, blocks[0].Hash, iterFn) {
		t.Error("Expected block not found")
	}

	file.Blocks = []protocol.BlockInfo{blocks[1]}
	file.Version = file.Version.Update(protocol.LocalDeviceID.Short())
	// Update index (removing old blocks)
	m.updateLocals("default", []protocol.FileInfo{file})

	if m.finder.Iterate(folders, blocks[0].Hash, iterFn) {
		t.Error("Unexpected block found")
	}

	if !m.finder.Iterate(folders, blocks[1].Hash, iterFn) {
		t.Error("Expected block not found")
	}

	file.Blocks = []protocol.BlockInfo{blocks[0]}
	file.Version = file.Version.Update(protocol.LocalDeviceID.Short())
	// Update index (removing old blocks)
	m.updateLocals("default", []protocol.FileInfo{file})

	if !m.finder.Iterate(folders, blocks[0].Hash, iterFn) {
		t.Error("Unexpected block found")
	}

	if m.finder.Iterate(folders, blocks[1].Hash, iterFn) {
		t.Error("Expected block not found")
	}
}

// shortcutFile sets file mode and modification time, when that's the only
// thing that has changed.
func (p *rwFolder) shortcutFile(file protocol.FileInfo) error {
	realName := filepath.Join(p.dir, file.Name)
	if !p.ignorePermissions(file) {
		if err := os.Chmod(realName, os.FileMode(file.Flags&0777)); err != nil {
			l.Infof("Puller (folder %q, file %q): shortcut: chmod: %v", p.folder, file.Name, err)
			p.newError(file.Name, err)
			return err
		}
	}

	t := time.Unix(file.Modified, 0)
	if err := os.Chtimes(realName, t, t); err != nil {
		// Try using virtual mtimes
		info, err := os.Stat(realName)
		if err != nil {
			l.Infof("Puller (folder %q, file %q): shortcut: unable to stat file: %v", p.folder, file.Name, err)
			p.newError(file.Name, err)
			return err
		}

		p.virtualMtimeRepo.UpdateMtime(file.Name, info.ModTime(), t)
	}

	// This may have been a conflict. We should merge the version vectors so
	// that our clock doesn't move backwards.
	if cur, ok := p.model.CurrentFolderFile(p.folder, file.Name); ok {
		file.Version = file.Version.Merge(cur.Version)
	}

	return nil
}

func getFile(db dbReader, key []byte) (protocol.FileInfo, bool) {
	bs, err := db.Get(key, nil)
	if err == leveldb.ErrNotFound {
		return protocol.FileInfo{}, false
	}
	if err != nil {
		panic(err)
	}

	var f protocol.FileInfo
	err = f.UnmarshalXDR(bs)
	if err != nil {
		panic(err)
	}
	return f, true
}

func dump(ldb *leveldb.DB) {
	it := ldb.NewIterator(nil, nil)
	var dev protocol.DeviceID
	for it.Next() {
		key := it.Key()
		switch key[0] {
		case db.KeyTypeDevice:
			folder := nulString(key[1 : 1+64])
			devBytes := key[1+64 : 1+64+32]
			name := nulString(key[1+64+32:])
			copy(dev[:], devBytes)
			fmt.Printf("[device] F:%q N:%q D:%v\n", folder, name, dev)

			var f protocol.FileInfo
			err := f.UnmarshalXDR(it.Value())
			if err != nil {
				log.Fatal(err)
			}
			fmt.Printf("  N:%q\n  F:%#o\n  M:%d\n  V:%v\n  S:%d\n  B:%d\n", f.Name, f.Flags, f.Modified, f.Version, f.Size(), len(f.Blocks))

		case db.KeyTypeGlobal:
			folder := nulString(key[1 : 1+64])
			name := nulString(key[1+64:])
			var flv db.VersionList
			flv.UnmarshalXDR(it.Value())
			fmt.Printf("[global] F:%q N:%q V: %s\n", folder, name, flv)

		case db.KeyTypeBlock:
			folder := nulString(key[1 : 1+64])
			hash := key[1+64 : 1+64+32]
			name := nulString(key[1+64+32:])
			fmt.Printf("[block] F:%q H:%x N:%q I:%d\n", folder, hash, name, binary.BigEndian.Uint32(it.Value()))

		case db.KeyTypeDeviceStatistic:
			fmt.Printf("[dstat]\n  %x\n  %x\n", it.Key(), it.Value())

		case db.KeyTypeFolderStatistic:
			fmt.Printf("[fstat]\n  %x\n  %x\n", it.Key(), it.Value())

		case db.KeyTypeVirtualMtime:
			fmt.Printf("[mtime]\n  %x\n  %x\n", it.Key(), it.Value())

		default:
			fmt.Printf("[???]\n  %x\n  %x\n", it.Key(), it.Value())
		}
	}
}

func ldbGet(db dbReader, folder, device, file []byte) (protocol.FileInfo, bool) {
	nk := deviceKey(folder, device, file)
	bs, err := db.Get(nk, nil)
	if err == leveldb.ErrNotFound {
		return protocol.FileInfo{}, false
	}
	if err != nil {
		panic(err)
	}

	var f protocol.FileInfo
	err = f.UnmarshalXDR(bs)
	if err != nil {
		panic(err)
	}
	return f, true
}

func SymlinkTypeEqual(disk symlinks.TargetType, f protocol.FileInfo) bool {
	// If the target is missing, Unix never knows what type of symlink it is
	// and Windows always knows even if there is no target. Which means that
	// without this special check a Unix node would be fighting with a Windows
	// node about whether or not the target is known. Basically, if you don't
	// know and someone else knows, just accept it. The fact that you don't
	// know means you are on Unix, and on Unix you don't really care what the
	// target type is. The moment you do know, and if something doesn't match,
	// that will propagate through the cluster.
	switch disk {
	case symlinks.TargetUnknown:
		return true
	case symlinks.TargetDirectory:
		return f.IsDirectory() && f.Flags&protocol.FlagSymlinkMissingTarget == 0
	case symlinks.TargetFile:
		return !f.IsDirectory() && f.Flags&protocol.FlagSymlinkMissingTarget == 0
	}
	panic("unknown symlink TargetType")
}

// deleteFile attempts to delete the given file
func (f *rwFolder) deleteFile(file protocol.FileInfo) {
	// Used in the defer closure below, updated by the function body. Take
	// care not declare another err.
	var err error

	events.Default.Log(events.ItemStarted, map[string]string{
		"folder": f.folderID,
		"item":   file.Name,
		"type":   "file",
		"action": "delete",
	})

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

	realName, err := rootedJoinedPath(f.dir, file.Name)
	if err != nil {
		f.newError(file.Name, err)
		return
	}

	cur, ok := f.model.CurrentFolderFile(f.folderID, file.Name)
	if ok && f.inConflict(cur.Version, file.Version) {
		// There is a conflict here. Move the file to a conflict copy instead
		// of deleting. Also merge with the version vector we had, to indicate
		// we have resolved the conflict.
		file.Version = file.Version.Merge(cur.Version)
		err = osutil.InWritableDir(f.moveForConflict, realName)
	} else if f.versioner != nil {
		err = osutil.InWritableDir(f.versioner.Archive, realName)
	} else {
		err = osutil.InWritableDir(os.Remove, realName)
	}

	if err == nil || os.IsNotExist(err) {
		// It was removed or it doesn't exist to start with
		f.dbUpdates <- dbUpdateJob{file, dbUpdateDeleteFile}
	} else if _, serr := f.mtimeFS.Lstat(realName); serr != nil && !os.IsPermission(serr) {
		// We get an error just looking at the file, and it's not a permission
		// problem. Lets assume the error is in fact some variant of "file
		// does not exist" (possibly expressed as some parent being a file and
		// not a directory etc) and that the delete is handled.
		f.dbUpdates <- dbUpdateJob{file, dbUpdateDeleteFile}
	} else {
		l.Infof("Puller (folder %q, file %q): delete: %v", f.folderID, file.Name, err)
		f.newError(file.Name, err)
	}
}

// shortcutFile sets file mode and modification time, when that's the only
// thing that has changed.
func (f *rwFolder) shortcutFile(file protocol.FileInfo) error {
	realName := filepath.Join(f.dir, file.Name)
	if !f.ignorePermissions(file) {
		if err := os.Chmod(realName, os.FileMode(file.Permissions&0777)); err != nil {
			l.Infof("Puller (folder %q, file %q): shortcut: chmod: %v", f.folderID, file.Name, err)
			f.newError(file.Name, err)
			return err
		}
	}

	f.mtimeFS.Chtimes(realName, file.ModTime(), file.ModTime()) // never fails

	// This may have been a conflict. We should merge the version vectors so
	// that our clock doesn't move backwards.
	if cur, ok := f.model.CurrentFolderFile(f.folderID, file.Name); ok {
		file.Version = file.Version.Merge(cur.Version)
	}

	return nil
}

// ldbUpdateGlobal adds this device+version to the version list for the given
// file. If the device is already present in the list, the version is updated.
// If the file does not have an entry in the global list, it is created.
func ldbUpdateGlobal(db dbReader, batch dbWriter, folder, device []byte, file protocol.FileInfo) bool {
	if debugDB {
		l.Debugf("update global; folder=%q device=%v file=%q version=%d", folder, protocol.DeviceIDFromBytes(device), file.Name, file.Version)
	}
	name := []byte(file.Name)
	gk := globalKey(folder, name)
	svl, err := db.Get(gk, nil)
	if err != nil && err != leveldb.ErrNotFound {
		panic(err)
	}

	var fl versionList

	// Remove the device from the current version list
	if svl != nil {
		err = fl.UnmarshalXDR(svl)
		if err != nil {
			panic(err)
		}

		for i := range fl.versions {
			if bytes.Compare(fl.versions[i].device, device) == 0 {
				if fl.versions[i].version.Equal(file.Version) {
					// No need to do anything
					return false
				}
				fl.versions = append(fl.versions[:i], fl.versions[i+1:]...)
				break
			}
		}
	}

	nv := fileVersion{
		device:  device,
		version: file.Version,
	}

	// Find a position in the list to insert this file. The file at the front
	// of the list is the newer, the "global".
	for i := range fl.versions {
		switch fl.versions[i].version.Compare(file.Version) {
		case protocol.Equal, protocol.Lesser:
			// The version at this point in the list is equal to or lesser
			// ("older") than us. We insert ourselves in front of it.
			fl.versions = insertVersion(fl.versions, i, nv)
			goto done

		case protocol.ConcurrentLesser, protocol.ConcurrentGreater:
			// The version at this point is in conflict with us. We must pull
			// the actual file metadata to determine who wins. If we win, we
			// insert ourselves in front of the loser here. (The "Lesser" and
			// "Greater" in the condition above is just based on the device
			// IDs in the version vector, which is not the only thing we use
			// to determine the winner.)
			of, ok := ldbGet(db, folder, fl.versions[i].device, name)
			if !ok {
				panic("file referenced in version list does not exist")
			}
			if file.WinsConflict(of) {
				fl.versions = insertVersion(fl.versions, i, nv)
				goto done
			}
		}
	}

	// We didn't find a position for an insert above, so append to the end.
	fl.versions = append(fl.versions, nv)

done:
	if debugDB {
		l.Debugf("batch.Put %p %x", batch, gk)
		l.Debugf("new global after update: %v", fl)
	}
	batch.Put(gk, fl.MustMarshalXDR())

	return true
}

// handleSymlink creates or updates the given symlink
func (f *rwFolder) handleSymlink(file protocol.FileInfo) {
	// Used in the defer closure below, updated by the function body. Take
	// care not declare another err.
	var err error

	events.Default.Log(events.ItemStarted, map[string]string{
		"folder": f.folderID,
		"item":   file.Name,
		"type":   "symlink",
		"action": "update",
	})

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

	realName, err := rootedJoinedPath(f.dir, file.Name)
	if err != nil {
		f.newError(file.Name, err)
		return
	}

	if shouldDebug() {
		curFile, _ := f.model.CurrentFolderFile(f.folderID, file.Name)
		l.Debugf("need symlink\n\t%v\n\t%v", file, curFile)
	}

	if len(file.SymlinkTarget) == 0 {
		// Index entry from a Syncthing predating the support for including
		// the link target in the index entry. We log this as an error.
		err = errors.New("incompatible symlink entry; rescan with newer Syncthing on source")
		l.Infof("Puller (folder %q, dir %q): %v", f.folderID, file.Name, err)
		f.newError(file.Name, err)
		return
	}

	if _, err = f.mtimeFS.Lstat(realName); err == nil {
		// There is already something under that name. Remove it to replace
		// with the symlink. This also handles the "change symlink type"
		// path.
		err = osutil.InWritableDir(os.Remove, realName)
		if err != nil {
			l.Infof("Puller (folder %q, dir %q): %v", f.folderID, file.Name, err)
			f.newError(file.Name, err)
			return
		}
	}

	tt := symlinks.TargetFile
	if file.IsDirectory() {
		tt = symlinks.TargetDirectory
	}

	// We declare a function that acts on only the path name, so
	// we can pass it to InWritableDir.
	createLink := func(path string) error {
		return symlinks.Create(path, file.SymlinkTarget, tt)
	}

	if err = osutil.InWritableDir(createLink, realName); err == nil {
		f.dbUpdates <- dbUpdateJob{file, dbUpdateHandleSymlink}
	} else {
		l.Infof("Puller (folder %q, dir %q): %v", f.folderID, file.Name, err)
		f.newError(file.Name, err)
	}
}

// Make sure that the copier routine hashes the content when asked, and pulls
// if it fails to find the block.
func TestLastResortPulling(t *testing.T) {
	db, _ := leveldb.Open(storage.NewMemStorage(), nil)
	m := NewModel(defaultConfig, protocol.LocalDeviceID, "device", "syncthing", "dev", db)
	m.AddFolder(defaultFolderConfig)

	// Add a file to index (with the incorrect block representation, as content
	// doesn't actually match the block list)
	file := protocol.FileInfo{
		Name:     "empty",
		Flags:    0,
		Modified: 0,
		Blocks:   []protocol.BlockInfo{blocks[0]},
	}
	m.updateLocals("default", []protocol.FileInfo{file})

	// Pretend that we are handling a new file of the same content but
	// with a different name (causing to copy that particular block)
	file.Name = "newfile"

	iterFn := func(folder, file string, index int32) bool {
		return true
	}

	// Check that that particular block is there
	if !m.finder.Iterate(folders, blocks[0].Hash, iterFn) {
		t.Error("Expected block not found")
	}

	p := rwFolder{
		folder:    "default",
		dir:       "testdata",
		model:     m,
		errors:    make(map[string]string),
		errorsMut: sync.NewMutex(),
	}

	copyChan := make(chan copyBlocksState)
	pullChan := make(chan pullBlockState, 1)
	finisherChan := make(chan *sharedPullerState, 1)

	// Run a single copier routine
	go p.copierRoutine(copyChan, pullChan, finisherChan)

	p.handleFile(file, copyChan, finisherChan)

	// Copier should hash empty file, realise that the region it has read
	// doesn't match the hash which was advertised by the block map, fix it
	// and ask to pull the block.
	<-pullChan

	// Verify that it did fix the incorrect hash.
	if m.finder.Iterate(folders, blocks[0].Hash, iterFn) {
		t.Error("Found unexpected block")
	}

	if !m.finder.Iterate(folders, scanner.SHA256OfNothing, iterFn) {
		t.Error("Expected block not found")
	}

	(<-finisherChan).fd.Close()
	os.Remove(filepath.Join("testdata", defTempNamer.TempName("newfile")))
}

// handleFile queues the copies and pulls as necessary for a single new or
// changed file.
func (p *rwFolder) handleFile(file protocol.FileInfo, copyChan chan<- copyBlocksState, finisherChan chan<- *sharedPullerState) {
	curFile, ok := p.model.CurrentFolderFile(p.folder, file.Name)

	if ok && len(curFile.Blocks) == len(file.Blocks) && scanner.BlocksEqual(curFile.Blocks, file.Blocks) {
		// We are supposed to copy the entire file, and then fetch nothing. We
		// are only updating metadata, so we don't actually *need* to make the
		// copy.
		l.Debugln(p, "taking shortcut on", file.Name)

		events.Default.Log(events.ItemStarted, map[string]string{
			"folder": p.folder,
			"item":   file.Name,
			"type":   "file",
			"action": "metadata",
		})

		p.queue.Done(file.Name)

		var err error
		if file.IsSymlink() {
			err = p.shortcutSymlink(file)
		} else {
			err = p.shortcutFile(file)
		}

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

		if err != nil {
			l.Infoln("Puller: shortcut:", err)
			p.newError(file.Name, err)
		} else {
			p.dbUpdates <- dbUpdateJob{file, dbUpdateShortcutFile}
		}

		return
	}

	if free, err := osutil.DiskFreeBytes(p.dir); err == nil && free < file.Size() {
		l.Warnf(`Folder "%s": insufficient disk space in %s for %s: have %.2f MiB, need %.2f MiB`, p.folder, p.dir, file.Name, float64(free)/1024/1024, float64(file.Size())/1024/1024)
		p.newError(file.Name, errors.New("insufficient space"))
		return
	}

	events.Default.Log(events.ItemStarted, map[string]string{
		"folder": p.folder,
		"item":   file.Name,
		"type":   "file",
		"action": "update",
	})

	scanner.PopulateOffsets(file.Blocks)

	// Figure out the absolute filenames we need once and for all
	tempName := filepath.Join(p.dir, defTempNamer.TempName(file.Name))
	realName := filepath.Join(p.dir, file.Name)

	reused := 0
	var blocks []protocol.BlockInfo

	// Check for an old temporary file which might have some blocks we could
	// reuse.
	tempBlocks, err := scanner.HashFile(tempName, protocol.BlockSize, 0, nil)
	if err == nil {
		// Check for any reusable blocks in the temp file
		tempCopyBlocks, _ := scanner.BlockDiff(tempBlocks, file.Blocks)

		// block.String() returns a string unique to the block
		existingBlocks := make(map[string]struct{}, len(tempCopyBlocks))
		for _, block := range tempCopyBlocks {
			existingBlocks[block.String()] = struct{}{}
		}

		// Since the blocks are already there, we don't need to get them.
		for _, block := range file.Blocks {
			_, ok := existingBlocks[block.String()]
			if !ok {
				blocks = append(blocks, block)
			}
		}

		// The sharedpullerstate will know which flags to use when opening the
		// temp file depending if we are reusing any blocks or not.
		reused = len(file.Blocks) - len(blocks)
		if reused == 0 {
			// Otherwise, discard the file ourselves in order for the
			// sharedpuller not to panic when it fails to exclusively create a
			// file which already exists
			osutil.InWritableDir(osutil.Remove, tempName)
		}
	} else {
		blocks = file.Blocks
	}
//.........这里部分代码省略.........

// handleFile queues the copies and pulls as necessary for a single new or
// changed file.
func (p *rwFolder) handleFile(file protocol.FileInfo, copyChan chan<- copyBlocksState, finisherChan chan<- *sharedPullerState) {
	curFile, hasCurFile := p.model.CurrentFolderFile(p.folder, file.Name)

	if hasCurFile && len(curFile.Blocks) == len(file.Blocks) && scanner.BlocksEqual(curFile.Blocks, file.Blocks) {
		// We are supposed to copy the entire file, and then fetch nothing. We
		// are only updating metadata, so we don't actually *need* to make the
		// copy.
		l.Debugln(p, "taking shortcut on", file.Name)

		events.Default.Log(events.ItemStarted, map[string]string{
			"folder": p.folder,
			"item":   file.Name,
			"type":   "file",
			"action": "metadata",
		})

		p.queue.Done(file.Name)

		var err error
		if file.IsSymlink() {
			err = p.shortcutSymlink(file)
		} else {
			err = p.shortcutFile(file)
		}

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

		if err != nil {
			l.Infoln("Puller: shortcut:", err)
			p.newError(file.Name, err)
		} else {
			p.dbUpdates <- dbUpdateJob{file, dbUpdateShortcutFile}
		}

		return
	}

	// Figure out the absolute filenames we need once and for all
	tempName := filepath.Join(p.dir, defTempNamer.TempName(file.Name))
	realName := filepath.Join(p.dir, file.Name)

	if hasCurFile && !curFile.IsDirectory() && !curFile.IsSymlink() {
		// Check that the file on disk is what we expect it to be according to
		// the database. If there's a mismatch here, there might be local
		// changes that we don't know about yet and we should scan before
		// touching the file. If we can't stat the file we'll just pull it.
		if info, err := osutil.Lstat(realName); err == nil {
			mtime := p.virtualMtimeRepo.GetMtime(file.Name, info.ModTime())
			if mtime.Unix() != curFile.Modified || info.Size() != curFile.Size() {
				l.Debugln("file modified but not rescanned; not pulling:", realName)
				// Scan() is synchronous (i.e. blocks until the scan is
				// completed and returns an error), but a scan can't happen
				// while we're in the puller routine. Request the scan in the
				// background and it'll be handled when the current pulling
				// sweep is complete. As we do retries, we'll queue the scan
				// for this file up to ten times, but the last nine of those
				// scans will be cheap...
				go p.Scan([]string{file.Name})
				return
			}
		}
	}

	scanner.PopulateOffsets(file.Blocks)

	reused := 0
	var blocks []protocol.BlockInfo
	var blocksSize int64

	// Check for an old temporary file which might have some blocks we could
	// reuse.
	tempBlocks, err := scanner.HashFile(tempName, protocol.BlockSize, 0, nil)
	if err == nil {
		// Check for any reusable blocks in the temp file
		tempCopyBlocks, _ := scanner.BlockDiff(tempBlocks, file.Blocks)

		// block.String() returns a string unique to the block
		existingBlocks := make(map[string]struct{}, len(tempCopyBlocks))
		for _, block := range tempCopyBlocks {
			existingBlocks[block.String()] = struct{}{}
		}

		// Since the blocks are already there, we don't need to get them.
		for _, block := range file.Blocks {
			_, ok := existingBlocks[block.String()]
			if !ok {
				blocks = append(blocks, block)
				blocksSize += int64(block.Size)
			}
		}

		// The sharedpullerstate will know which flags to use when opening the
//.........这里部分代码省略.........