class ServiceProviderExtensionStorage extends ExtensionStorage {

    @Override
    public Map<String, Set<String>> read() {
        Map<String, Set<String>> extensions = new HashMap<>();

        for (String extensionPoint : processor.getExtensions().keySet()) {
            try {
                FileObject file = getFiler().getResource(StandardLocation.CLASS_OUTPUT, "", EXTENSIONS_RESOURCE
                    + "/" + extensionPoint);
                Set<String> entries = new HashSet<>();
                ExtensionStorage.read(file.openReader(true), entries);
                extensions.put(extensionPoint, entries);
            } catch (FileNotFoundException | NoSuchFileException e) {
                // doesn't exist, ignore
            } catch (FilerException e) {
                // re-opening the file for reading or after writing is ignorable
            } catch (IOException e) {
                error(e.getMessage());
            }
        }

        return extensions;
    }

    public  ServiceProviderExtensionStorage(ExtensionAnnotationProcessor processor);

}