sleep method

@override Future<void> sleep(Duration duration, CancellationSignal cancellation)

Wait for duration while observing cancellation.

Implementations must reject negative durations. A cancellation request is cooperative: it ends this wait, but it cannot forcefully cancel unrelated Dart Futures.

Implementation

@override
Future<void> sleep(Duration duration, CancellationSignal cancellation) async {
  if (duration.isNegative) {
    throw ArgumentError.value(duration, 'duration', 'must not be negative');
  }

  cancellation.throwIfCancelled();
  if (duration == Duration.zero) {
    await Future<void>.value();
    cancellation.throwIfCancelled();
    return;
  }

  final pending = _ManualSleep(
    deadline: _now.add(duration),
    completer: Completer<void>.sync(),
  );
  _pending.add(pending);

  try {
    await Future.any<void>(<Future<void>>[
      pending.completer.future,
      cancellation.whenCancelled,
    ]);
    cancellation.throwIfCancelled();
  } finally {
    _pending.remove(pending);
  }
}