addFile method
Implementation
Future<void> addFile(File file, [String? filename]) async {
final fileStream = InputFileStream(file.path);
final f =
ArchiveFile.stream(filename ?? path.basename(file.path), fileStream);
f.lastModTime = (await file.lastModified()).millisecondsSinceEpoch ~/ 1000;
f.mode = (await file.stat()).mode;
_encoder.add(f);
await fileStream.close();
}