1 // Copyright 2014 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 COMPONENTS_KEYED_SERVICE_CONTENT_REFCOUNTED_BROWSER_CONTEXT_KEYED_SERVICE_H_ 6 #define COMPONENTS_KEYED_SERVICE_CONTENT_REFCOUNTED_BROWSER_CONTEXT_KEYED_SERVICE_H_ 7 8 #include "base/memory/ref_counted.h" 9 #include "base/sequenced_task_runner_helpers.h" 10 #include "components/keyed_service/core/keyed_service_export.h" 11 #include "content/public/browser/browser_thread.h" 12 13 class RefcountedBrowserContextKeyedService; 14 15 namespace impl { 16 17 struct KEYED_SERVICE_EXPORT RefcountedBrowserContextKeyedServiceTraits { 18 static void Destruct(const RefcountedBrowserContextKeyedService* obj); 19 }; 20 21 } // namespace impl 22 23 // Base class for refcounted objects that hang off the BrowserContext. 24 // 25 // The two pass shutdown described in KeyedService works a bit differently 26 // because there could be outstanding references on other threads. 27 // ShutdownOnUIThread() will be called on the UI thread, and then the 28 // destructor will run when the last reference is dropped, which may or may not 29 // be after the corresponding BrowserContext has been destroyed. 30 // 31 // Optionally, if you initialize your service with the constructor that takes a 32 // thread ID, your service will be deleted on that thread. We can't use 33 // content::DeleteOnThread<> directly because 34 // RefcountedBrowserContextKeyedService must be one type that 35 // RefcountedBrowserContextKeyedServiceFactory can use. 36 class KEYED_SERVICE_EXPORT RefcountedBrowserContextKeyedService 37 : public base::RefCountedThreadSafe< 38 RefcountedBrowserContextKeyedService, 39 impl::RefcountedBrowserContextKeyedServiceTraits> { 40 public: 41 // Unlike KeyedService, ShutdownOnUI is not optional. You must do something 42 // to drop references during the first pass Shutdown() because this is the 43 // only point where you are guaranteed that something is running on the UI 44 // thread. The PKSF framework will ensure that this is only called on the UI 45 // thread; you do not need to check for that yourself. 46 virtual void ShutdownOnUIThread() = 0; 47 48 protected: 49 // If your service does not need to be deleted on a specific thread, use the 50 // default constructor. 51 RefcountedBrowserContextKeyedService(); 52 53 // If you need your service to be deleted on a specific thread (for example, 54 // you're converting a service that used content::DeleteOnThread<IO>), then 55 // use this constructor with the ID of the thread. 56 explicit RefcountedBrowserContextKeyedService( 57 const content::BrowserThread::ID thread_id); 58 59 // The second pass destruction can happen anywhere unless you specify which 60 // thread this service must be destroyed on by using the second constructor. 61 virtual ~RefcountedBrowserContextKeyedService(); 62 63 private: 64 friend struct impl::RefcountedBrowserContextKeyedServiceTraits; 65 friend class base::DeleteHelper<RefcountedBrowserContextKeyedService>; 66 friend class base::RefCountedThreadSafe< 67 RefcountedBrowserContextKeyedService, 68 impl::RefcountedBrowserContextKeyedServiceTraits>; 69 70 // Do we have to delete this object on a specific thread? 71 bool requires_destruction_on_thread_; 72 content::BrowserThread::ID thread_id_; 73 }; 74 75 #endif // COMPONENTS_KEYED_SERVICE_CONTENT_REFCOUNTED_BROWSER_CONTEXT_KEYED_SERVICE_H_ 76
