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Add WaitHandleAsyncFactory

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cinder
2025-05-06 20:38:30 -05:00
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commit a2a4f3d82c
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LibreMetaverse/Threading/WaitHandleAsyncFactory.cs Normal file
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/*
* Copyright (c) 2014 Stephen Cleary
* Copyright (c) 2025, Sjofn LLC.
* All rights reserved.
*
* - Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* - Neither the name of the openmetaverse.co nor the names
* of its contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
using System;
using System.Threading.Tasks;
using System.Threading;
namespace LibreMetaverse.Threading
{
public static class WaitHandleAsyncFactory
{
/// <summary>
/// Wraps a <see cref="WaitHandle"/> with a <see cref="Task"/>.
/// When the <see cref="WaitHandle"/> is signalled, the returned <see cref="Task"/> is completed.
/// If the handle is already signalled, this method acts synchronously.
/// </summary>
/// <param name="handle">The <see cref="WaitHandle"/> to observe.</param>
public static Task FromWaitHandle(WaitHandle handle)
{
return FromWaitHandle(handle, Timeout.InfiniteTimeSpan, CancellationToken.None);
}
/// <summary>
/// Wraps a <see cref="WaitHandle"/> with a <see cref="Task{Boolean}"/>.
/// If the <see cref="WaitHandle"/> is signalled, the returned task is completed with a <c>true</c> result.
/// If the observation times out, the returned task is completed with a <c>false</c> result.
/// If the handle is already signalled or the timeout is zero, this method acts synchronously.
/// </summary>
/// <param name="handle">The <see cref="WaitHandle"/> to observe.</param>
/// <param name="timeout">The timeout after which the <see cref="WaitHandle"/> is no longer observed.</param>
public static Task<bool> FromWaitHandle(WaitHandle handle, TimeSpan timeout)
{
return FromWaitHandle(handle, timeout, CancellationToken.None);
}
/// <summary>
/// Wraps a <see cref="WaitHandle"/> with a <see cref="Task{Boolean}"/>.
/// If the <see cref="WaitHandle"/> is signalled, the returned task is (successfully) completed.
/// If the observation is cancelled, the returned task is cancelled.
/// If the handle is already signalled or the cancellation token is already cancelled, this method acts synchronously.
/// </summary>
/// <param name="handle">The <see cref="WaitHandle"/> to observe.</param>
/// <param name="token">The cancellation token that cancels observing the <see cref="WaitHandle"/>.</param>
public static Task FromWaitHandle(WaitHandle handle, CancellationToken token)
{
return FromWaitHandle(handle, Timeout.InfiniteTimeSpan, token);
}
/// <summary>
/// Wraps a <see cref="WaitHandle"/> with a <see cref="Task{Boolean}"/>.
/// If the <see cref="WaitHandle"/> is signalled, the returned task is completed with a <c>true</c> result.
/// If the observation times out, the returned task is completed with a <c>false</c> result.
/// If the observation is cancelled, the returned task is cancelled.
/// If the handle has already signalled, the timeout is zero,
/// or the cancellation token has already cancelled, then this method acts synchronously.
/// </summary>
/// <param name="handle">The <see cref="WaitHandle"/> to observe.</param>
/// <param name="timeout">The timeout after which the <see cref="WaitHandle"/> is no longer observed.</param>
/// <param name="token">The cancellation token that cancels observing the <see cref="WaitHandle"/>.</param>
public static Task<bool> FromWaitHandle(WaitHandle handle, TimeSpan timeout, CancellationToken token)
{
_ = handle ?? throw new ArgumentNullException(nameof(handle));
// Handle synchronous cases.
var alreadySignalled = handle.WaitOne(0);
if (alreadySignalled)
return Task.FromResult(true);
if (timeout == TimeSpan.Zero)
return Task.FromResult(false);
if (token.IsCancellationRequested)
return Task.FromCanceled<bool>(new CancellationToken(true));
// Register all asynchronous cases.
return DoFromWaitHandle(handle, timeout, token);
}
private static async Task<bool> DoFromWaitHandle(WaitHandle handle, TimeSpan timeout, CancellationToken token)
{
var tcs = new TaskCompletionSource<bool>();
using (new ThreadPoolRegistration(handle, timeout, tcs))
using (token.Register(state => ((TaskCompletionSource<bool>)state).TrySetCanceled(),
tcs, useSynchronizationContext: false))
return await tcs.Task.ConfigureAwait(false);
}
private sealed class ThreadPoolRegistration : IDisposable
{
private readonly RegisteredWaitHandle _registeredWaitHandle;
public ThreadPoolRegistration(WaitHandle handle, TimeSpan timeout, TaskCompletionSource<bool> tcs)
{
_registeredWaitHandle = ThreadPool.RegisterWaitForSingleObject(handle,
(state, timedOut) => ((TaskCompletionSource<bool>)state).TrySetResult(!timedOut), tcs,
timeout, executeOnlyOnce: true);
}
void IDisposable.Dispose() => _registeredWaitHandle.Unregister(null);
}
}
}