ios/web/webui/url_data_source_ios_impl.h

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