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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CHROME_BROWSER_ANDROID_PROVIDER_BLOCKING_UI_THREAD_ASYNC_REQUEST_H_
      6 #define CHROME_BROWSER_ANDROID_PROVIDER_BLOCKING_UI_THREAD_ASYNC_REQUEST_H_
      7 
      8 #include "base/bind.h"
      9 #include "base/callback.h"
     10 #include "base/synchronization/waitable_event.h"
     11 #include "chrome/browser/android/provider/run_on_ui_thread_blocking.h"
     12 #include "content/public/browser/browser_thread.h"
     13 
     14 // Allows making async requests and blocking the current thread until the
     15 // response arrives. The request is performed in the UI thread.
     16 // Users of this class MUST call RequestCompleted when receiving the response.
     17 // Cannot be called directly from the UI thread.
     18 class BlockingUIThreadAsyncRequest {
     19  public:
     20   BlockingUIThreadAsyncRequest();
     21 
     22   // Runs an asynchronous request, blocking the invoking thread until a response
     23   // is received. Class users MUST call RequestCompleted when this happens.
     24   // Make sure that the response is also delivered to the UI thread.
     25   // The request argument can be defined using base::Bind.
     26   template <typename Signature>
     27   void RunAsyncRequestOnUIThreadBlocking(base::Callback<Signature> request) {
     28     DCHECK(!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
     29 
     30     // Make the request in the UI thread.
     31     request_completed_.Reset();
     32     RunOnUIThreadBlocking::Run(
     33         base::Bind(
     34             &BlockingUIThreadAsyncRequest::RunRequestOnUIThread<Signature>,
     35             request));
     36 
     37     // Wait until the request callback invokes Finished.
     38     request_completed_.Wait();
     39   }
     40 
     41   // Notifies about a finished request.
     42   void RequestCompleted();
     43 
     44  private:
     45   template <typename Signature>
     46   static void RunRequestOnUIThread(base::Callback<Signature> request) {
     47     request.Run();
     48   }
     49 
     50   base::WaitableEvent request_completed_;
     51 
     52   DISALLOW_COPY_AND_ASSIGN(BlockingUIThreadAsyncRequest);
     53 };
     54 
     55 #endif  // CHROME_BROWSER_ANDROID_PROVIDER_BLOCKING_UI_THREAD_ASYNC_REQUEST_H_
     56