chrome/browser/android/provider/blocking_ui_thread_async_request.h

   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_