async-locks

Synchronization primitives for asynchronous Dart code, inspired from Python

Usage

With Lock

• Can be used to guarantee exclusive access to a shared resource.

var lock = Lock();
await lock.acquire();
// access the shared resource here
// ...
lock.release();

• Starting from v1.1.0, you can use the lock.run method.

var lock = Lock();
var result = await lock.run(() async {
  // access shared resource
  // ...
});

With Event

• Can be used to notify multiple futures that an event has occured.

import "package:async_locks/async_locks.dart";

class Program {
  final event = Event();

  Future<void> mainFuture() async {
    print("Running mainFuture");
    await Future.delayed(const Duration(seconds: 3));
    print("Completing mainFuture");
    event.set();
  }

  Future<void> runFuture(int n) async {
    print("Started Future-$n. Waiting for mainFuture to complete");
    await event.wait();
    print("Future-$n completed");
  }

  Future<void> run() async {
    print("Running program");
    await Future.wait([mainFuture(), runFuture(1), runFuture(2), runFuture(3), runFuture(4)]);
    print("Finished!");
  }
}

void main() async {
  var program = Program();
  await program.run();
}

In this example, each runFuture waits for the event to be set in mainFuture.

Both Lock and Event are fair: the first proceeding future will be the future that called await lock.acquire() or await event.wait() first (though this is usually less important when using Event as all futures will be awaken anyway).