1 // Copyright (c) 2013 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 CONTENT_BROWSER_WEBUI_URL_DATA_SOURCE_IMPL_H_ 6 #define CONTENT_BROWSER_WEBUI_URL_DATA_SOURCE_IMPL_H_ 7 8 #include "base/memory/ref_counted.h" 9 #include "base/memory/scoped_ptr.h" 10 #include "base/sequenced_task_runner_helpers.h" 11 #include "content/browser/webui/url_data_manager.h" 12 #include "content/common/content_export.h" 13 14 namespace base { 15 class RefCountedMemory; 16 } 17 18 namespace content { 19 class URLDataManagerBackend; 20 class URLDataSource; 21 class URLDataSourceImpl; 22 23 // Trait used to handle deleting a URLDataSource. Deletion happens on the UI 24 // thread. 25 // 26 // Implementation note: the normal shutdown sequence is for the UI loop to 27 // stop pumping events then the IO loop and thread are stopped. When the 28 // URLDataSources are no longer referenced (which happens when IO thread stops) 29 // they get added to the UI message loop for deletion. But because the UI loop 30 // has stopped by the time this happens the URLDataSources would be leaked. 31 // 32 // To make sure URLDataSources are properly deleted URLDataManager manages 33 // deletion of the URLDataSources. When a URLDataSource is no longer referenced 34 // it is added to |data_sources_| and a task is posted to the UI thread to 35 // handle the actual deletion. During shutdown |DeleteDataSources| is invoked so 36 // that all pending URLDataSources are properly deleted. 37 struct DeleteURLDataSource { DestructDeleteURLDataSource38 static void Destruct(const URLDataSourceImpl* data_source) { 39 URLDataManager::DeleteDataSource(data_source); 40 } 41 }; 42 43 // A URLDataSource is an object that can answer requests for data 44 // asynchronously. URLDataSources are collectively owned with refcounting smart 45 // pointers and should never be deleted on the IO thread, since their calls 46 // are handled almost always on the UI thread and there's a possibility of a 47 // data race. The |DeleteDataSource| trait above is used to enforce this. 48 class URLDataSourceImpl : public base::RefCountedThreadSafe< 49 URLDataSourceImpl, DeleteURLDataSource> { 50 public: 51 // See source_name_ below for docs on that parameter. Takes ownership of 52 // |source|. 53 URLDataSourceImpl(const std::string& source_name, 54 URLDataSource* source); 55 56 // Report that a request has resulted in the data |bytes|. 57 // If the request can't be satisfied, pass NULL for |bytes| to indicate 58 // the request is over. 59 virtual void SendResponse(int request_id, base::RefCountedMemory* bytes); 60 source_name()61 const std::string& source_name() const { return source_name_; } source()62 URLDataSource* source() const { return source_.get(); } 63 64 protected: 65 virtual ~URLDataSourceImpl(); 66 67 private: 68 friend class URLDataManager; 69 friend class URLDataManagerBackend; 70 friend class base::DeleteHelper<URLDataSourceImpl>; 71 72 // SendResponse invokes this on the IO thread. Notifies the backend to 73 // handle the actual work of sending the data. 74 virtual void SendResponseOnIOThread( 75 int request_id, 76 scoped_refptr<base::RefCountedMemory> bytes); 77 78 // The name of this source. 79 // E.g., for favicons, this could be "favicon", which results in paths for 80 // specific resources like "favicon/34" getting sent to this source. 81 const std::string source_name_; 82 83 // This field is set and maintained by URLDataManagerBackend. It is set when 84 // the DataSource is added, and unset if the DataSource is removed. A 85 // DataSource can be removed in two ways: the URLDataManagerBackend is 86 // deleted, or another DataSource is registered with the same name. backend_ 87 // should only be accessed on the IO thread. This reference can't be via a 88 // scoped_refptr else there would be a cycle between the backend and data 89 // source. 90 URLDataManagerBackend* backend_; 91 92 scoped_ptr<URLDataSource> source_; 93 }; 94 95 } // namespace content 96 97 #endif // CONTENT_BROWSER_WEBUI_URL_DATA_SOURCE_IMPL_H_ 98