Locks

package:weblocks ports web concurrency primitives to all Dart platforms.

This package includes a read-write lock implementation that:

• works across isolates on native platforms, and across tabs and workers on the web.
• is asynchronous.
• supports shared and exclusive access to locks.
• identifies mutexes by name, and doesn't require prior communication or SendPort setup.
• can query the state of mutexes.

On the web, package:weblocks is implemented with of the Web Locks API. On native platforms, dart:ffi is used with a native lock implementation written in Rust. Of course, both platforms use an identical API, and share tests to behave the same.

In addition to locks, this package also ports the BroadcastChannel API to native platforms.

Getting started

Note that this package requires the native-assets experiment, meaning that it is currently only available on beta builds of the Dart SDK.

Apart from that, dart pub add weblocks is the only step to install this package. Build hooks will automatically download native sources where required.

Usage

The LockManager interface is the main entrypoint to request locks, available through the lockManager getter:

import 'package:weblocks/weblocks.dart';

void main() async {
  final lockName = 'my-lock';

  final held = await lockManager.request(lockName).completion;
  print('Holds lock: ${held != null}'); // true

  held!.release();
}

Broadcast channels

To exchange broadcast messages between isolates, use BroadcastChannel instances created through LockManager.broadcastChannel:

// These methods can run on different isolates, tabs, or web workers.
void send() {
  final channel = lockManager.broadcastChannel('foo');
  channel.send('hello');
}

void receive() async {
  final channel = lockManager.broadcastChannel('foo');
  await for (final message in channel) {
    print('From channel: $message');
  }
}

For more details, see the documentation or the full example.

Development

To work on this package, consider adding the hooks section in the pubspec.yaml that is currently commented out to use a debug build of the native code for the current host.