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mtimefs.go
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mtimefs.go
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// Copyright (C) 2016 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package fs
import (
"errors"
"time"
)
// The database is where we store the virtual mtimes
type database interface {
Bytes(key string) (data []byte, ok bool, err error)
PutBytes(key string, data []byte) error
Delete(key string) error
}
type mtimeFS struct {
Filesystem
chtimes func(string, time.Time, time.Time) error
db database
caseInsensitive bool
}
type MtimeFSOption func(*mtimeFS)
func WithCaseInsensitivity(v bool) MtimeFSOption {
return func(f *mtimeFS) {
f.caseInsensitive = v
}
}
type optionMtime struct {
db database
options []MtimeFSOption
}
// NewMtimeOption makes any filesystem provide nanosecond mtime precision,
// regardless of what shenanigans the underlying filesystem gets up to.
func NewMtimeOption(db database, options ...MtimeFSOption) Option {
return &optionMtime{
db: db,
options: options,
}
}
func (o *optionMtime) apply(fs Filesystem) Filesystem {
f := &mtimeFS{
Filesystem: fs,
chtimes: fs.Chtimes, // for mocking it out in the tests
db: o.db,
}
for _, opt := range o.options {
opt(f)
}
return f
}
func (*optionMtime) String() string {
return "mtime"
}
func (f *mtimeFS) Chtimes(name string, atime, mtime time.Time) error {
// Do a normal Chtimes call, don't care if it succeeds or not.
f.chtimes(name, atime, mtime)
// Stat the file to see what happened. Here we *do* return an error,
// because it might be "does not exist" or similar.
info, err := f.Filesystem.Lstat(name)
if err != nil {
return err
}
f.save(name, info.ModTime(), mtime)
return nil
}
func (f *mtimeFS) Stat(name string) (FileInfo, error) {
info, err := f.Filesystem.Stat(name)
if err != nil {
return nil, err
}
mtimeMapping, err := f.load(name)
if err != nil {
return nil, err
}
if mtimeMapping.Real.Equal(info.ModTime()) {
info = mtimeFileInfo{
FileInfo: info,
mtime: mtimeMapping.Virtual,
}
}
return info, nil
}
func (f *mtimeFS) Lstat(name string) (FileInfo, error) {
info, err := f.Filesystem.Lstat(name)
if err != nil {
return nil, err
}
mtimeMapping, err := f.load(name)
if err != nil {
return nil, err
}
if mtimeMapping.Real.Equal(info.ModTime()) {
info = mtimeFileInfo{
FileInfo: info,
mtime: mtimeMapping.Virtual,
}
}
return info, nil
}
func (f *mtimeFS) Create(name string) (File, error) {
fd, err := f.Filesystem.Create(name)
if err != nil {
return nil, err
}
return mtimeFile{fd, f}, nil
}
func (f *mtimeFS) Open(name string) (File, error) {
fd, err := f.Filesystem.Open(name)
if err != nil {
return nil, err
}
return mtimeFile{fd, f}, nil
}
func (f *mtimeFS) OpenFile(name string, flags int, mode FileMode) (File, error) {
fd, err := f.Filesystem.OpenFile(name, flags, mode)
if err != nil {
return nil, err
}
return mtimeFile{fd, f}, nil
}
func (f *mtimeFS) underlying() (Filesystem, bool) {
return f.Filesystem, true
}
func (*mtimeFS) wrapperType() filesystemWrapperType {
return filesystemWrapperTypeMtime
}
func (f *mtimeFS) save(name string, real, virtual time.Time) {
if f.caseInsensitive {
name = UnicodeLowercaseNormalized(name)
}
if real.Equal(virtual) {
// If the virtual time and the real on disk time are equal we don't
// need to store anything.
f.db.Delete(name)
return
}
mtime := MtimeMapping{
Real: real,
Virtual: virtual,
}
bs, _ := mtime.Marshal() // Can't fail
f.db.PutBytes(name, bs)
}
func (f *mtimeFS) load(name string) (MtimeMapping, error) {
if f.caseInsensitive {
name = UnicodeLowercaseNormalized(name)
}
data, exists, err := f.db.Bytes(name)
if err != nil {
return MtimeMapping{}, err
} else if !exists {
return MtimeMapping{}, nil
}
var mtime MtimeMapping
if err := mtime.Unmarshal(data); err != nil {
return MtimeMapping{}, err
}
return mtime, nil
}
// The mtimeFileInfo is an os.FileInfo that lies about the ModTime().
type mtimeFileInfo struct {
FileInfo
mtime time.Time
}
func (m mtimeFileInfo) ModTime() time.Time {
return m.mtime
}
type mtimeFile struct {
File
fs *mtimeFS
}
func (f mtimeFile) Stat() (FileInfo, error) {
info, err := f.File.Stat()
if err != nil {
return nil, err
}
mtimeMapping, err := f.fs.load(f.Name())
if err != nil {
return nil, err
}
if mtimeMapping.Real.Equal(info.ModTime()) {
info = mtimeFileInfo{
FileInfo: info,
mtime: mtimeMapping.Virtual,
}
}
return info, nil
}
// Used by copyRange to unwrap to the real file and access SyscallConn
func (f mtimeFile) unwrap() File {
return f.File
}
// MtimeMapping represents the mapping as stored in the database
type MtimeMapping struct {
// "Real" is the on disk timestamp
Real time.Time `json:"real"`
// "Virtual" is what want the timestamp to be
Virtual time.Time `json:"virtual"`
}
func (t *MtimeMapping) Marshal() ([]byte, error) {
bs0, _ := t.Real.MarshalBinary()
bs1, _ := t.Virtual.MarshalBinary()
return append(bs0, bs1...), nil
}
func (t *MtimeMapping) Unmarshal(bs []byte) error {
if err := t.Real.UnmarshalBinary(bs[:len(bs)/2]); err != nil {
return err
}
if err := t.Virtual.UnmarshalBinary(bs[len(bs)/2:]); err != nil {
return err
}
return nil
}
func GetMtimeMapping(fs Filesystem, file string) (MtimeMapping, error) {
fs, ok := unwrapFilesystem(fs, filesystemWrapperTypeMtime)
if !ok {
return MtimeMapping{}, errors.New("failed to unwrap")
}
mtimeFs, ok := fs.(*mtimeFS)
if !ok {
return MtimeMapping{}, errors.New("unwrapping failed")
}
return mtimeFs.load(file)
}