mirror of
https://github.com/restic/restic.git
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241 lines
5.7 KiB
Go
241 lines
5.7 KiB
Go
package cache
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import (
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"fmt"
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"io"
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"os"
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"path/filepath"
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"runtime"
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"github.com/pkg/errors"
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"github.com/restic/restic/internal/backend"
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"github.com/restic/restic/internal/backend/util"
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"github.com/restic/restic/internal/crypto"
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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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func (c *Cache) filename(h backend.Handle) string {
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if len(h.Name) < 2 {
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panic("Name is empty or too short")
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}
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subdir := h.Name[:2]
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return filepath.Join(c.path, cacheLayoutPaths[h.Type], subdir, h.Name)
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}
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func (c *Cache) canBeCached(t backend.FileType) bool {
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if c == nil {
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return false
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}
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_, ok := cacheLayoutPaths[t]
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return ok
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}
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// load returns a reader that yields the contents of the file with the
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// given handle. rd must be closed after use. If an error is returned, the
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// ReadCloser is nil. The bool return value indicates whether the requested
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// file exists in the cache. It can be true even when no reader is returned
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// because length or offset are out of bounds
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func (c *Cache) load(h backend.Handle, length int, offset int64) (io.ReadCloser, bool, error) {
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debug.Log("Load(%v, %v, %v) from cache", h, length, offset)
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if !c.canBeCached(h.Type) {
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return nil, false, errors.New("cannot be cached")
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}
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f, err := fs.Open(c.filename(h))
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if err != nil {
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return nil, false, errors.WithStack(err)
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}
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fi, err := f.Stat()
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if err != nil {
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_ = f.Close()
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return nil, true, errors.WithStack(err)
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}
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size := fi.Size()
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if size <= int64(crypto.CiphertextLength(0)) {
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_ = f.Close()
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return nil, true, errors.Errorf("cached file %v is truncated", h)
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}
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if size < offset+int64(length) {
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_ = f.Close()
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return nil, true, errors.Errorf("cached file %v is too short", h)
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}
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if offset > 0 {
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if _, err = f.Seek(offset, io.SeekStart); err != nil {
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_ = f.Close()
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return nil, true, err
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}
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}
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if length <= 0 {
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return f, true, nil
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}
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return util.LimitReadCloser(f, int64(length)), true, nil
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}
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// save saves a file in the cache.
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func (c *Cache) save(h backend.Handle, rd io.Reader) error {
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debug.Log("Save to cache: %v", h)
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if rd == nil {
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return errors.New("Save() called with nil reader")
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}
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if !c.canBeCached(h.Type) {
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return errors.New("cannot be cached")
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}
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finalname := c.filename(h)
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dir := filepath.Dir(finalname)
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err := fs.Mkdir(dir, 0700)
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if err != nil && !errors.Is(err, os.ErrExist) {
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return err
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}
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// First save to a temporary location. This allows multiple concurrent
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// restics to use a single cache dir.
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f, err := os.CreateTemp(dir, "tmp-")
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if err != nil {
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return err
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}
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n, err := io.Copy(f, rd)
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if err != nil {
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_ = f.Close()
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_ = fs.Remove(f.Name())
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return errors.Wrap(err, "Copy")
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}
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if n <= int64(crypto.CiphertextLength(0)) {
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_ = f.Close()
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_ = fs.Remove(f.Name())
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debug.Log("trying to cache truncated file %v, removing", h)
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return nil
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}
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// Close, then rename. Windows doesn't like the reverse order.
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if err = f.Close(); err != nil {
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_ = fs.Remove(f.Name())
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return errors.WithStack(err)
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}
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err = fs.Rename(f.Name(), finalname)
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if err != nil {
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_ = fs.Remove(f.Name())
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}
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if runtime.GOOS == "windows" && errors.Is(err, os.ErrPermission) {
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// On Windows, renaming over an existing file is ok
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// (os.Rename is MoveFileExW with MOVEFILE_REPLACE_EXISTING
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// since Go 1.5), but not when someone else has the file open.
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//
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// When we get Access denied, we assume that's the case
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// and the other process has written the desired contents to f.
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err = nil
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}
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return errors.WithStack(err)
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}
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func (c *Cache) Forget(h backend.Handle) error {
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h.IsMetadata = false
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if _, ok := c.forgotten.Load(h); ok {
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// Delete a file at most once while restic runs.
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// This prevents repeatedly caching and forgetting broken files
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return fmt.Errorf("circuit breaker prevents repeated deletion of cached file %v", h)
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}
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removed, err := c.remove(h)
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if removed {
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c.forgotten.Store(h, struct{}{})
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}
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return err
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}
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// remove deletes a file. When the file is not cached, no error is returned.
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func (c *Cache) remove(h backend.Handle) (bool, error) {
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if !c.canBeCached(h.Type) {
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return false, nil
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}
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err := fs.Remove(c.filename(h))
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removed := err == nil
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if errors.Is(err, os.ErrNotExist) {
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err = nil
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}
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return removed, err
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}
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// Clear removes all files of type t from the cache that are not contained in
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// the set valid.
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func (c *Cache) Clear(t restic.FileType, valid restic.IDSet) error {
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debug.Log("Clearing cache for %v: %v valid files", t, len(valid))
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if !c.canBeCached(t) {
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return nil
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}
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list, err := c.list(t)
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if err != nil {
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return err
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}
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for id := range list {
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if valid.Has(id) {
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continue
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}
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// ignore ErrNotExist to gracefully handle multiple processes running Clear() concurrently
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if err = fs.Remove(c.filename(backend.Handle{Type: t, Name: id.String()})); err != nil && !errors.Is(err, os.ErrNotExist) {
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return err
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}
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}
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return nil
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}
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func isFile(fi os.FileInfo) bool {
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return fi.Mode()&(os.ModeType|os.ModeCharDevice) == 0
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}
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// list returns a list of all files of type T in the cache.
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func (c *Cache) list(t restic.FileType) (restic.IDSet, error) {
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if !c.canBeCached(t) {
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return nil, errors.New("cannot be cached")
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}
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list := restic.NewIDSet()
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dir := filepath.Join(c.path, cacheLayoutPaths[t])
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err := filepath.Walk(dir, func(name string, fi os.FileInfo, err error) error {
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if err != nil {
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return errors.Wrap(err, "Walk")
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}
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if !isFile(fi) {
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return nil
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}
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id, err := restic.ParseID(filepath.Base(name))
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if err != nil {
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return nil
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}
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list.Insert(id)
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return nil
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})
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return list, err
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}
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// Has returns true if the file is cached.
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func (c *Cache) Has(h backend.Handle) bool {
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if !c.canBeCached(h.Type) {
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return false
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}
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_, err := fs.Stat(c.filename(h))
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return err == nil
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}
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