package cache import ( "fmt" "io/ioutil" "os" "path/filepath" "strconv" "github.com/pkg/errors" "github.com/restic/restic/internal/debug" "github.com/restic/restic/internal/fs" "github.com/restic/restic/internal/restic" ) // Cache manages a local cache. type Cache struct { Path string Base string PerformReadahead func(restic.Handle) bool } const dirMode = 0700 const fileMode = 0600 func readVersion(dir string) (v uint, err error) { buf, err := ioutil.ReadFile(filepath.Join(dir, "version")) if os.IsNotExist(err) { return 0, nil } if err != nil { return 0, errors.Wrap(err, "ReadFile") } ver, err := strconv.ParseUint(string(buf), 10, 32) if err != nil { return 0, errors.Wrap(err, "ParseUint") } return uint(ver), nil } const cacheVersion = 1 // ensure Cache implements restic.Cache var _ restic.Cache = &Cache{} var cacheLayoutPaths = map[restic.FileType]string{ restic.DataFile: "data", restic.SnapshotFile: "snapshots", restic.IndexFile: "index", } const cachedirTagSignature = "Signature: 8a477f597d28d172789f06886806bc55\n" func writeCachedirTag(dir string) error { if err := fs.MkdirAll(dir, dirMode); err != nil { return err } f, err := fs.OpenFile(filepath.Join(dir, "CACHEDIR.TAG"), os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0644) if err != nil { if os.IsExist(errors.Cause(err)) { return nil } return errors.Wrap(err, "OpenFile") } debug.Log("Create CACHEDIR.TAG at %v", dir) if _, err := f.Write([]byte(cachedirTagSignature)); err != nil { _ = f.Close() return errors.Wrap(err, "Write") } return f.Close() } // New returns a new cache for the repo ID at basedir. If basedir is the empty // string, the default cache location (according to the XDG standard) is used. // // For partial files, the complete file is loaded and stored in the cache when // performReadahead returns true. func New(id string, basedir string) (c *Cache, err error) { if basedir == "" { basedir, err = defaultCacheDir() if err != nil { return nil, err } } // create base dir and tag it as a cache directory if err = writeCachedirTag(basedir); err != nil { return nil, err } cachedir := filepath.Join(basedir, id) debug.Log("using cache dir %v", cachedir) v, err := readVersion(cachedir) if err != nil { return nil, err } if v > cacheVersion { return nil, errors.New("cache version is newer") } // create the repo cache dir if it does not exist yet if err = fs.MkdirAll(cachedir, dirMode); err != nil { return nil, err } if v < cacheVersion { err = ioutil.WriteFile(filepath.Join(cachedir, "version"), []byte(fmt.Sprintf("%d", cacheVersion)), 0644) if err != nil { return nil, errors.Wrap(err, "WriteFile") } } for _, p := range cacheLayoutPaths { if err = fs.MkdirAll(filepath.Join(cachedir, p), dirMode); err != nil { return nil, err } } c = &Cache{ Path: cachedir, Base: basedir, PerformReadahead: func(restic.Handle) bool { // do not perform readahead by default return false }, } return c, nil } // errNoSuchFile is returned when a file is not cached. type errNoSuchFile struct { Type string Name string } func (e errNoSuchFile) Error() string { return fmt.Sprintf("file %v (%v) is not cached", e.Name, e.Type) } // IsNotExist returns true if the error was caused by a non-existing file. func (c *Cache) IsNotExist(err error) bool { _, ok := errors.Cause(err).(errNoSuchFile) return ok } // Wrap returns a backend with a cache. func (c *Cache) Wrap(be restic.Backend) restic.Backend { return newBackend(be, c) } // BaseDir returns the base directory. func (c *Cache) BaseDir() string { return c.Base }