nametransform: add Dir() function

Dir is like filepath.Dir but returns "" instead of ".".
This was already implemented in fusefrontend_reverse as saneDir().

We will need it in nametransform for the improved diriv caching.

internal/fusefrontend_reverse/reverse_longnames.go

@@ -86,7 +86,7 @@ func (rfs *ReverseFS) newNameFile(relPath string) (nodefs.File, fuse.Status) {
 	dotName := filepath.Base(relPath)                                    // gocryptfs.longname.XYZ.name
 	longname := dotName[:len(dotName)-len(nametransform.LongNameSuffix)] // gocryptfs.longname.XYZ
 	// cipher directory
-	cDir := saneDir(relPath)
+	cDir := nametransform.Dir(relPath)
 	// plain directory
 	pDir, err := rfs.decryptPath(cDir)
 	if err != nil {

internal/fusefrontend_reverse/rpath.go

@@ -11,15 +11,6 @@ import (
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
-// saneDir is like filepath.Dir but returns "" instead of "."
-func saneDir(path string) string {
-	d := filepath.Dir(path)
-	if d == "." {
-		return ""
-	}
-	return d
-}
-
 // abs basically returns storage dir + "/" + relPath.
 // It takes an error parameter so it can directly wrap decryptPath like this:
 // a, err := rfs.abs(rfs.decryptPath(relPath))
@@ -71,7 +62,7 @@ func (rfs *ReverseFS) decryptPath(relPath string) (string, error) {
 		return relPath, nil
 	}
 	// Check if the parent dir is in the cache
-	cDir := saneDir(relPath)
+	cDir := nametransform.Dir(relPath)
 	dirIV, pDir := rPathCache.lookup(cDir)
 	if dirIV != nil {
 		cName := filepath.Base(relPath)
@@ -95,6 +86,6 @@ func (rfs *ReverseFS) decryptPath(relPath string) (string, error) {
 		transformedParts = append(transformedParts, transformedPart)
 	}
 	pRelPath := filepath.Join(transformedParts...)
-	rPathCache.store(cDir, dirIV, saneDir(pRelPath))
+	rPathCache.store(cDir, dirIV, nametransform.Dir(pRelPath))
 	return pRelPath, nil
 }

internal/fusefrontend_reverse/virtualfile.go

@@ -7,6 +7,7 @@ import (
 	"github.com/hanwen/go-fuse/fuse"
 	"github.com/hanwen/go-fuse/fuse/nodefs"
 
+	"github.com/rfjakob/gocryptfs/internal/nametransform"
 	"github.com/rfjakob/gocryptfs/internal/pathiv"
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
@@ -31,7 +32,7 @@ const (
 )
 
 func (rfs *ReverseFS) newDirIVFile(cRelPath string) (nodefs.File, fuse.Status) {
-	cDir := saneDir(cRelPath)
+	cDir := nametransform.Dir(cRelPath)
 	absDir, err := rfs.abs(rfs.decryptPath(cDir))
 	if err != nil {
 		return nil, fuse.ToStatus(err)

internal/nametransform/diriv.go

@@ -162,3 +162,12 @@ func (be *NameTransform) EncryptPathDirIV(plainPath string, rootDir string) (cip
 	be.DirIVCache.Store(parentDir, iv, cParentDir)
 	return cipherPath, nil
 }
+
+// Dir is like filepath.Dir but returns "" instead of ".".
+func Dir(path string) string {
+	d := filepath.Dir(path)
+	if d == "." {
+		return ""
+	}
+	return d
+}