x64 视频下载器

////// ffmpeg 处理
typedef _DownloadM3U8N = Uint64 Function(
    Pointer<ffi.Utf16> url, Pointer<ffi.Utf16> outFile, Pointer onState, Uint32 timeout);
typedef _DownloadM3U8D = int Function(
    Pointer<ffi.Utf16> url, Pointer<ffi.Utf16> outFile, Pointer onState, int timeout);

typedef _StopDownloadM3U8N = Void Function(Uint64 handle);
typedef _StopDownloadM3U8D = void Function(int handle);

typedef _GetDownloadM3U8StatusN = Int32 Function(Uint64 handle, Pointer<Uint32> recv, Pointer<Uint32> total);
typedef _GetDownloadM3U8StatusD = int Function(int handle, Pointer<Uint32> recv, Pointer<Uint32> total);

class FFMpegWin {
  static DynamicLibrary? _library;
  static Pointer<void> nil = Pointer.fromAddress(0);

  static void windowsInit() {
    if (_library != null) return;
    const dll = "video_down.dll";
    try {
      _library = DynamicLibrary.open(dll);
    } catch (e) {
      stderr.writeln('Failed to load $dll');
      rethrow;
    }
  }

  /// 转换下载好的本地 m3u8 文件为 mp4
  /// 
  /// 处理结果：-1 任务不存在， 0 初始化中, 1 下载中，2 下载成功完成，3 下载超时结束，4 未知原因下载失败
  static Future<int> localM3u8ToMP4(String indexFile, String outFile) async {
    if (Platform.isWindows) {
      windowsInit();
    } else {
      return -1;
    }
    final downloadM3U8 = _library!.lookupFunction<_DownloadM3U8N, _DownloadM3U8D>("DownloadM3U8");
    final getDownState = _library!.lookupFunction<_GetDownloadM3U8StatusN, _GetDownloadM3U8StatusD>("GetDownloadM3U8Status");
    // final stopDownloadM3U8 = _library!.lookupFunction<_StopDownloadM3U8N, _StopDownloadM3U8D>("StopDownloadM3U8");
    final Pointer<ffi.Utf16> url = indexFile.toNativeUtf16();
    final Pointer<ffi.Utf16> out = outFile.toNativeUtf16();
    final Pointer<Uint32> recv = ffi.malloc.call<Uint32>();
    final Pointer<Uint32> total = ffi.malloc.call<Uint32>();
    int result = 0;
    try {
      final handle = downloadM3U8(url, out, nil as dynamic, 60000);
      if (handle != 0) {
        while (true) {
          await Utils.sleep(300);
          // 获取下载状态： -1 任务不存在， 0 初始化中, 1 下载中，2 下载成功完成，3 下载超时结束，4 未知原因下载失败
          result = getDownState(handle, recv, total);
          if (result > 1 || result == -1) break;
        }
      }
    } finally {
      ffi.malloc.free(url);
      ffi.malloc.free(out);
      ffi.malloc.free(recv);
      ffi.malloc.free(total);
    }
    return result;
  }

}