extend virtual folders support to all storage backends

Fixes #241

vfs/gcsfs.go

@@ -35,8 +35,10 @@ var (
 
 // GCSFs is a Fs implementation for Google Cloud Storage.
 type GCSFs struct {
-	connectionID   string
-	localTempDir   string
+	connectionID string
+	localTempDir string
+	// if not empty this fs is mouted as virtual folder in the specified path
+	mountPath      string
 	config         *GCSFsConfig
 	svc            *storage.Client
 	ctxTimeout     time.Duration
@@ -48,11 +50,16 @@ func init() {
 }
 
 // NewGCSFs returns an GCSFs object that allows to interact with Google Cloud Storage
-func NewGCSFs(connectionID, localTempDir string, config GCSFsConfig) (Fs, error) {
+func NewGCSFs(connectionID, localTempDir, mountPath string, config GCSFsConfig) (Fs, error) {
+	if localTempDir == "" {
+		localTempDir = filepath.Clean(os.TempDir())
+	}
+
 	var err error
 	fs := &GCSFs{
 		connectionID:   connectionID,
 		localTempDir:   localTempDir,
+		mountPath:      mountPath,
 		config:         &config,
 		ctxTimeout:     30 * time.Second,
 		ctxLongTimeout: 300 * time.Second,
@@ -152,7 +159,7 @@ func (fs *GCSFs) Open(name string, offset int64) (File, *pipeat.PipeReaderAt, fu
 	ctx, cancelFn := context.WithCancel(context.Background())
 	objectReader, err := obj.NewRangeReader(ctx, offset, -1)
 	if err == nil && offset > 0 && objectReader.Attrs.ContentEncoding == "gzip" {
-		err = fmt.Errorf("Range request is not possible for gzip content encoding, requested offset %v", offset)
+		err = fmt.Errorf("range request is not possible for gzip content encoding, requested offset %v", offset)
 		objectReader.Close()
 	}
 	if err != nil {
@@ -230,7 +237,7 @@ func (fs *GCSFs) Rename(source, target string) error {
 			return err
 		}
 		if hasContents {
-			return fmt.Errorf("Cannot rename non empty directory: %#v", source)
+			return fmt.Errorf("cannot rename non empty directory: %#v", source)
 		}
 	}
 	src := fs.svc.Bucket(fs.config.Bucket).Object(source)
@@ -266,7 +273,7 @@ func (fs *GCSFs) Remove(name string, isDir bool) error {
 			return err
 		}
 		if hasContents {
-			return fmt.Errorf("Cannot remove non empty directory: %#v", name)
+			return fmt.Errorf("cannot remove non empty directory: %#v", name)
 		}
 	}
 	ctx, cancelFn := context.WithDeadline(context.Background(), time.Now().Add(fs.ctxTimeout))
@@ -290,6 +297,11 @@ func (fs *GCSFs) Mkdir(name string) error {
 	return w.Close()
 }
 
+// MkdirAll does nothing, we don't have folder
+func (*GCSFs) MkdirAll(name string, uid int, gid int) error {
+	return nil
+}
+
 // Symlink creates source as a symbolic link to target.
 func (*GCSFs) Symlink(source, target string) error {
 	return ErrVfsUnsupported
@@ -441,7 +453,7 @@ func (*GCSFs) IsNotSupported(err error) bool {
 // CheckRootPath creates the specified local root directory if it does not exists
 func (fs *GCSFs) CheckRootPath(username string, uid int, gid int) bool {
 	// we need a local directory for temporary files
-	osFs := NewOsFs(fs.ConnectionID(), fs.localTempDir, nil)
+	osFs := NewOsFs(fs.ConnectionID(), fs.localTempDir, "")
 	return osFs.CheckRootPath(username, uid, gid)
 }
 
@@ -510,6 +522,9 @@ func (fs *GCSFs) GetRelativePath(name string) string {
 		}
 		rel = path.Clean("/" + strings.TrimPrefix(rel, "/"+fs.config.KeyPrefix))
 	}
+	if fs.mountPath != "" {
+		rel = path.Join(fs.mountPath, rel)
+	}
 	return rel
 }
 
@@ -578,6 +593,9 @@ func (GCSFs) HasVirtualFolders() bool {
 
 // ResolvePath returns the matching filesystem path for the specified virtual path
 func (fs *GCSFs) ResolvePath(virtualPath string) (string, error) {
+	if fs.mountPath != "" {
+		virtualPath = strings.TrimPrefix(virtualPath, fs.mountPath)
+	}
 	if !path.IsAbs(virtualPath) {
 		virtualPath = path.Clean("/" + virtualPath)
 	}