backend/cache: use backend types not restic types (#21860)

internal/backend/cache/file.go

@@ -12,7 +12,6 @@ import (
 	"github.com/restic/restic/internal/backend/util"
 	"github.com/restic/restic/internal/crypto"
 	"github.com/restic/restic/internal/debug"
-	"github.com/restic/restic/internal/restic"
 )
 
 func (c *Cache) filename(h backend.Handle) string {
@@ -171,7 +170,7 @@ func (c *Cache) remove(h backend.Handle) (bool, error) {
 
 // Clear removes all files of type t from the cache that are not contained in
 // the set valid.
-func (c *Cache) Clear(t restic.FileType, valid restic.IDSet) error {
+func (c *Cache) Clear(t backend.FileType, valid map[string]struct{}) error {
 	debug.Log("Clearing cache for %v: %v valid files", t, len(valid))
 	if !c.canBeCached(t) {
 		return nil
@@ -183,12 +182,12 @@ func (c *Cache) Clear(t restic.FileType, valid restic.IDSet) error {
 	}
 
 	for id := range list {
-		if valid.Has(id) {
+		if _, ok := valid[id]; ok {
 			continue
 		}
 
 		// ignore ErrNotExist to gracefully handle multiple processes running Clear() concurrently
-		if err = os.Remove(c.filename(backend.Handle{Type: t, Name: id.String()})); err != nil && !errors.Is(err, os.ErrNotExist) {
+		if err = os.Remove(c.filename(backend.Handle{Type: t, Name: id})); err != nil && !errors.Is(err, os.ErrNotExist) {
 			return err
 		}
 	}
@@ -201,12 +200,12 @@ func isFile(fi os.FileInfo) bool {
 }
 
 // list returns a list of all files of type T in the cache.
-func (c *Cache) list(t restic.FileType) (restic.IDSet, error) {
+func (c *Cache) list(t backend.FileType) (map[string]struct{}, error) {
 	if !c.canBeCached(t) {
 		return nil, errors.New("cannot be cached")
 	}
 
-	list := restic.NewIDSet()
+	list := make(map[string]struct{})
 	dir := filepath.Join(c.path, cacheLayoutPaths[t])
 	err := filepath.Walk(dir, func(name string, fi os.FileInfo, err error) error {
 		if err != nil {
@@ -221,12 +220,8 @@ func (c *Cache) list(t restic.FileType) (restic.IDSet, error) {
 			return nil
 		}
 
-		id, err := restic.ParseID(filepath.Base(name))
-		if err != nil {
-			return nil
-		}
-
-		list.Insert(id)
+		id := filepath.Base(name)
+		list[id] = struct{}{}
 		return nil
 	})