blob: b697e78e0f4f0df13033abf86df285f954ecd640 [file] [log] [blame]
// Copyright (c) 2021, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import 'dart:async';
import 'dart:collection';
/// Used to protect global state accessed in blocks containing calls to
/// asynchronous methods.
class Mutex {
/// Executes a block of code containing asynchronous calls atomically.
/// If no other asynchronous context is currently executing within
/// [criticalSection], it will immediately be called. Otherwise, the caller
/// will be suspended and entered into a queue to be resumed once the lock is
/// released.
Future<T> runGuarded<T>(FutureOr<T> Function() criticalSection) async {
try {
await _acquireLock();
return await criticalSection();
} finally {
Future<void> _acquireLock() async {
if (!_locked) {
_locked = true;
final request = Completer<void>();
await request.future;
void _releaseLock() {
_locked = false;
if (_outstandingRequests.isNotEmpty) {
final request = _outstandingRequests.removeFirst();
bool _locked = false;
final _outstandingRequests = Queue<Completer<void>>();