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fluffychat/lib/utils/stream_extension.dart

47 lines
1.5 KiB
Dart

import 'dart:async';
extension StreamExtension on Stream {
/// Returns a new Stream which outputs only `true` for every update of the original
/// stream, ratelimited by the Duration t
Stream<bool> rateLimit(Duration t) {
final controller = StreamController<bool>();
Timer timer;
var gotMessage = false;
// as we call our inline-defined function recursively we need to make sure that the
// variable exists prior of creating the function. Silly dart.
Function _onMessage;
// callback to determine if we should send out an update
_onMessage = () {
// do nothing if it is already closed
if (controller.isClosed) {
return;
}
if (timer == null) {
// if we don't have a timer yet, send out the update and start a timer
gotMessage = false;
controller.add(true);
timer = Timer(t, () {
// the timer has ended...delete it and, if we got a message, re-run the
// method to send out an update!
timer = null;
if (gotMessage) {
_onMessage();
}
});
} else {
// set that we got a message
gotMessage = true;
}
};
final subscription = listen((_) => _onMessage(),
onDone: () => controller.close(),
onError: (e, s) => controller.addError(e, s));
// add proper cleanup to the subscription and the controller, to not memory leak
controller.onCancel = () {
subscription.cancel();
controller.close();
};
return controller.stream;
}
}