swift: add ListP interface - #4788

backend/swift/swift.go

@@ -773,21 +773,20 @@ func (f *Fs) list(ctx context.Context, container, directory, prefix string, addC
 }
 
 // listDir lists a single directory
-func (f *Fs) listDir(ctx context.Context, container, directory, prefix string, addContainer bool) (entries fs.DirEntries, err error) {
+func (f *Fs) listDir(ctx context.Context, container, directory, prefix string, addContainer bool, callback func(fs.DirEntry) error) (err error) {
 	if container == "" {
-		return nil, fs.ErrorListBucketRequired
+		return fs.ErrorListBucketRequired
 	}
 	// List the objects
 	err = f.list(ctx, container, directory, prefix, addContainer, false, false, func(entry fs.DirEntry) error {
-		entries = append(entries, entry)
+		return callback(entry)
-		return nil
 	})
 	if err != nil {
-		return nil, err
+		return err
 	}
 	// container must be present if listing succeeded
 	f.cache.MarkOK(container)
-	return entries, nil
+	return nil
 }
 
 // listContainers lists the containers
@@ -818,14 +817,46 @@ func (f *Fs) listContainers(ctx context.Context) (entries fs.DirEntries, err err
 // This should return ErrDirNotFound if the directory isn't
 // found.
 func (f *Fs) List(ctx context.Context, dir string) (entries fs.DirEntries, err error) {
+	return list.WithListP(ctx, dir, f)
+}
+
+// ListP lists the objects and directories of the Fs starting
+// from dir non recursively into out.
+//
+// dir should be "" to start from the root, and should not
+// have trailing slashes.
+//
+// This should return ErrDirNotFound if the directory isn't
+// found.
+//
+// It should call callback for each tranche of entries read.
+// These need not be returned in any particular order.  If
+// callback returns an error then the listing will stop
+// immediately.
+func (f *Fs) ListP(ctx context.Context, dir string, callback fs.ListRCallback) error {
+	list := list.NewHelper(callback)
 	container, directory := f.split(dir)
 	if container == "" {
 		if directory != "" {
-			return nil, fs.ErrorListBucketRequired
+			return fs.ErrorListBucketRequired
 		}
-		return f.listContainers(ctx)
+		entries, err := f.listContainers(ctx)
+		if err != nil {
+			return err
 		}
-	return f.listDir(ctx, container, directory, f.rootDirectory, f.rootContainer == "")
+		for _, entry := range entries {
+			err = list.Add(entry)
+			if err != nil {
+				return err
+			}
+		}
+	} else {
+		err := f.listDir(ctx, container, directory, f.rootDirectory, f.rootContainer == "", list.Add)
+		if err != nil {
+			return err
+		}
+	}
+	return list.Flush()
 }
 
 // ListR lists the objects and directories of the Fs starting
@@ -1650,6 +1681,7 @@ var (
 	_ fs.PutStreamer = &Fs{}
 	_ fs.Copier      = &Fs{}
 	_ fs.ListRer     = &Fs{}
+	_ fs.ListPer     = &Fs{}
 	_ fs.Object      = &Object{}
 	_ fs.MimeTyper   = &Object{}
 )