55 lines
1.7 KiB
C#
55 lines
1.7 KiB
C#
//------------------------------------------------------------------------------
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// <copyright file="CountdownTask.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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//------------------------------------------------------------------------------
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namespace System.Web.Util {
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using System;
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using System.Threading;
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using System.Threading.Tasks;
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// This class is similar to CountdownEvent, but it uses Task under the covers
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// instead of ManualResetEvent. When the internal counter hits zero, the Task
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// is marked as complete.
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//
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// This type is thread-safe. Error checking is not performed in RET builds.
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internal sealed class CountdownTask {
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private int _pendingCount;
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private readonly TaskCompletionSource<object> _tcs = new TaskCompletionSource<object>();
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public CountdownTask(int initialCount) {
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AddCount(initialCount);
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}
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public int CurrentCount {
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get { return _pendingCount; }
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}
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public Task Task {
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get { return _tcs.Task; }
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}
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private void AddCount(int delta) {
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int newCount = Interlocked.Add(ref _pendingCount, delta);
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Debug.Assert(newCount >= 0, "The counter should never hit a negative value.");
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if (newCount == 0) {
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bool success = _tcs.TrySetResult(null);
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Debug.Assert(success, "TrySetResult shouldn't have been already called.");
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}
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}
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public void MarkOperationCompleted() {
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AddCount(-1);
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}
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public void MarkOperationPending() {
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AddCount(+1);
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}
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}
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}
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