| /* |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| namespace DotPulsar.Internal |
| { |
| using Exceptions; |
| using System; |
| using System.Collections.Generic; |
| using System.Threading; |
| using System.Threading.Tasks; |
| |
| public sealed class AsyncLock : IAsyncDisposable |
| { |
| private readonly LinkedList<CancelableCompletionSource<IDisposable>> _pending; |
| private readonly SemaphoreSlim _semaphoreSlim; |
| private readonly Releaser _releaser; |
| private readonly Task<IDisposable> _completedTask; |
| private int _isDisposed; |
| |
| public AsyncLock() |
| { |
| _pending = new LinkedList<CancelableCompletionSource<IDisposable>>(); |
| _semaphoreSlim = new SemaphoreSlim(1, 1); |
| _releaser = new Releaser(Release); |
| _completedTask = Task.FromResult((IDisposable) _releaser); |
| } |
| |
| public Task<IDisposable> Lock(CancellationToken cancellationToken) |
| { |
| LinkedListNode<CancelableCompletionSource<IDisposable>>? node = null; |
| |
| lock (_pending) |
| { |
| ThrowIfDisposed(); |
| |
| if (_semaphoreSlim.CurrentCount == 1) //Lock is free |
| { |
| _semaphoreSlim.Wait(cancellationToken); //Will never block |
| return _completedTask; |
| } |
| |
| //Lock was not free |
| var ccs = new CancelableCompletionSource<IDisposable>(); |
| node = _pending.AddLast(ccs); |
| } |
| |
| cancellationToken.Register(() => Cancel(node)); |
| |
| return node.Value.Task; |
| } |
| |
| public async ValueTask DisposeAsync() |
| { |
| lock (_pending) |
| { |
| if (Interlocked.Exchange(ref _isDisposed, 1) != 0) |
| return; |
| |
| foreach (var pending in _pending) |
| pending.Dispose(); |
| |
| _pending.Clear(); |
| } |
| |
| await _semaphoreSlim.WaitAsync().ConfigureAwait(false); //Wait for possible lock-holder to finish |
| |
| _semaphoreSlim.Release(); |
| _semaphoreSlim.Dispose(); |
| } |
| |
| private void Cancel(LinkedListNode<CancelableCompletionSource<IDisposable>> node) |
| { |
| lock (_pending) |
| { |
| try |
| { |
| _pending.Remove(node); |
| node.Value.Dispose(); |
| } |
| catch |
| { |
| // Ignore |
| } |
| } |
| } |
| |
| private void Release() |
| { |
| lock (_pending) |
| { |
| var node = _pending.First; |
| if (node is not null) |
| { |
| node.Value.SetResult(_releaser); |
| node.Value.Dispose(); |
| _pending.RemoveFirst(); |
| return; |
| } |
| |
| if (_semaphoreSlim.CurrentCount == 0) |
| _semaphoreSlim.Release(); |
| } |
| } |
| |
| private void ThrowIfDisposed() |
| { |
| if (_isDisposed != 0) |
| throw new AsyncLockDisposedException(); |
| } |
| |
| private class Releaser : IDisposable |
| { |
| private readonly Action _release; |
| |
| public Releaser(Action release) |
| => _release = release; |
| |
| public void Dispose() |
| => _release(); |
| } |
| } |
| } |