decodeBuffer method Null safety

Implementation

Archive decodeBuffer(InputStreamBase input,
    {bool verify = false, String? password}) {
  directory = ZipDirectory.read(input, password: password);
  final archive = Archive();

  for (final zfh in directory.fileHeaders) {
    final zf = zfh.file!;

    // The attributes are stored in base 8
    final mode = zfh.externalFileAttributes!;
    final compress = zf.compressionMethod != ZipFile.STORE;

    if (verify) {
      final computedCrc = getCrc32(zf.content);
      if (computedCrc != zf.crc32) {
        throw ArchiveException('Invalid CRC for file in archive.');
      }
    }

    dynamic content = zf.rawContent;
    var file = ArchiveFile(
        zf.filename, zf.uncompressedSize!, content, zf.compressionMethod);

    file.mode = mode >> 16;

    // see https://github.com/brendan-duncan/archive/issues/21
    // UNIX systems has a creator version of 3 decimal at 1 byte offset
    if (zfh.versionMadeBy >> 8 == 3) {
      //final bool isDirectory = file.mode & 0x7000 == 0x4000;
      final isFile = file.mode & 0x3F000 == 0x8000;
      file.isFile = isFile;
    } else {
      file.isFile = !file.name.endsWith('/');
    }

    file.crc32 = zf.crc32;
    file.compress = compress;
    file.lastModTime = zf.lastModFileDate << 16 | zf.lastModFileTime;

    archive.addFile(file);
  }

  return archive;
}