// Copyright © 2019 The CefSharp Authors. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
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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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namespace CefSharp.Internals
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{
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/// <summary>
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/// ConcurrentMethodRunnerQueue - Async Javascript Binding methods are run
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/// on the ThreadPool in parallel, when a method returns a Task
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/// the we use ContinueWith to be notified of completion then
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/// raise the MethodInvocationComplete event
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/// </summary>
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public class ConcurrentMethodRunnerQueue : IMethodRunnerQueue
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{
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private readonly JavascriptObjectRepository repository;
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private CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
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public event EventHandler<MethodInvocationCompleteArgs> MethodInvocationComplete;
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public ConcurrentMethodRunnerQueue(JavascriptObjectRepository repository)
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{
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this.repository = repository;
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}
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public void Dispose()
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{
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cancellationTokenSource.Cancel();
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}
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public void Enqueue(MethodInvocation methodInvocation)
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{
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var task = new Task(() =>
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{
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var result = ExecuteMethodInvocation(methodInvocation);
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//If the call failed or returned null then we'll fire the event immediately
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if (!result.Success || result.Result == null)
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{
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OnMethodInvocationComplete(result, cancellationTokenSource.Token);
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}
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else
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{
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var resultType = result.Result.GetType();
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//If the returned type is Task then we'll ContinueWith and perform the processing then.
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if (typeof(Task).IsAssignableFrom(resultType))
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{
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var resultTask = (Task)result.Result;
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if (resultType.IsGenericType)
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{
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resultTask.ContinueWith((t) =>
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{
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if (t.Status == TaskStatus.RanToCompletion)
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{
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//We use some reflection to get the Result
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//If someone has a better way of doing this then please submit a PR
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result.Result = resultType.GetProperty("Result").GetValue(resultTask);
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}
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else
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{
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result.Success = false;
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result.Result = null;
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var aggregateException = t.Exception;
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//TODO: Add support for passing a more complex message
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// to better represent the Exception
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if (aggregateException.InnerExceptions.Count == 1)
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{
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result.Message = aggregateException.InnerExceptions[0].ToString();
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}
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else
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{
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result.Message = t.Exception.ToString();
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}
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}
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OnMethodInvocationComplete(result, cancellationTokenSource.Token);
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},
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cancellationTokenSource.Token, TaskContinuationOptions.None, TaskScheduler.Default);
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}
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else
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{
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//If it's not a generic Task then it doesn't have a return object
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//So we'll just set the result to null and continue on
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result.Result = null;
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OnMethodInvocationComplete(result, cancellationTokenSource.Token);
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}
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}
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else
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{
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OnMethodInvocationComplete(result, cancellationTokenSource.Token);
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}
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}
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}, cancellationTokenSource.Token);
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task.Start(TaskScheduler.Default);
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}
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private MethodInvocationResult ExecuteMethodInvocation(MethodInvocation methodInvocation)
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{
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object result = null;
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string exception;
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var success = false;
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//make sure we don't throw exceptions in the executor task
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try
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{
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success = repository.TryCallMethod(methodInvocation.ObjectId, methodInvocation.MethodName, methodInvocation.Parameters.ToArray(), out result, out exception);
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}
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catch (Exception e)
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{
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exception = e.Message;
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}
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return new MethodInvocationResult
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{
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BrowserId = methodInvocation.BrowserId,
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CallbackId = methodInvocation.CallbackId,
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FrameId = methodInvocation.FrameId,
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Message = exception,
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Result = result,
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Success = success
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};
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}
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private void OnMethodInvocationComplete(MethodInvocationResult e, CancellationToken token)
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{
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//If cancellation has been requested we don't need to continue.
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if (!token.IsCancellationRequested)
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{
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MethodInvocationComplete?.Invoke(this, new MethodInvocationCompleteArgs(e));
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}
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}
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}
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}
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