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