Attempt 3 at: Splits ChromeURLDataManager into 2 chunks:...

chrome/browser/dom_ui/chrome_url_data_manager.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_DOM_UI_CHROME_URL_DATA_MANAGER_H_
 #define CHROME_BROWSER_DOM_UI_CHROME_URL_DATA_MANAGER_H_
 #pragma once
 
 #include <map>
 #include <string>
 
-#include "base/singleton.h"
 #include "base/task.h"
 #include "base/ref_counted.h"
 #include "chrome/browser/browser_thread.h"
 
+class ChromeURLDataManagerBackend;
 class DictionaryValue;
 class FilePath;
-class GURL;
 class MessageLoop;
+class Profile;
 class RefCountedMemory;
-class URLRequestChromeJob;
-
-namespace net {
-class URLRequest;
-class URLRequestJob;
-}  // namespace net
 
 // To serve dynamic data off of chrome: URLs, implement the
 // ChromeURLDataManager::DataSource interface and register your handler
-// with AddDataSource.
-
-// ChromeURLDataManager lives on the IO thread, so any interfacing with
-// it from the UI thread needs to go through an InvokeLater.
+// with AddDataSource. DataSources must be added on the UI thread (they are also
+// deleted on the UI thread). Internally the DataSources are maintained by
+// ChromeURLDataManagerBackend, see it for details.
 class ChromeURLDataManager {
  public:
-  // Returns the singleton instance.
-  static ChromeURLDataManager* GetInstance();
+  class DataSource;
 
-  typedef int RequestID;
+  // Trait used to handle deleting a DataSource. Deletion happens on the UI
+  // thread.
+  //
+  // Implementation note: the normal shutdown sequence is for the UI loop to
+  // stop pumping events then the IO loop and thread are stopped. When the
+  // DataSources are no longer referenced (which happens when IO thread stops)
+  // they get added to the UI message loop for deletion. But because the UI loop
+  // has stopped by the time this happens the DataSources would be leaked.
+  //
+  // To make sure DataSources are properly deleted ChromeURLDataManager manages
+  // deletion of the DataSources.  When a DataSource is no longer referenced it
+  // is added to |data_sources_| and a task is posted to the UI thread to handle
+  // the actual deletion. During shutdown |DeleteDataSources| is invoked so that
+  // all pending DataSources are properly deleted.
+  struct DeleteDataSource {
+    static void Destruct(const DataSource* data_source) {
+      ChromeURLDataManager::DeleteDataSource(data_source);
+    }
+  };
 
   // A DataSource is an object that can answer requests for data
   // asynchronously. DataSources are collectively owned with refcounting smart
   // pointers and should never be deleted on the IO thread, since their calls
   // are handled almost always on the UI thread and there's a possibility of a
   // data race.  The |DeleteOnUIThread| trait is used to enforce this.

[Lei Zhang, 2011/03/04 12:30:55]

This comment is out of date. Can you fix?

   //
   // An implementation of DataSource should handle calls to
   // StartDataRequest() by starting its (implementation-specific) asynchronous
   // request for the data, then call SendResponse() to notify.
   class DataSource : public base::RefCountedThreadSafe<
-      DataSource, BrowserThread::DeleteOnUIThread> {
+      DataSource, DeleteDataSource> {
    public:
     // See source_name_ and message_loop_ below for docs on these parameters.
-    DataSource(const std::string& source_name,
-               MessageLoop* message_loop);
+    DataSource(const std::string& source_name, MessageLoop* message_loop);
 
     // Sent by the DataManager to request data at |path|.  The source should
     // call SendResponse() when the data is available or if the request could
     // not be satisfied.
     virtual void StartDataRequest(const std::string& path,
                                   bool is_off_the_record,
                                   int request_id) = 0;
 
     // Return the mimetype that should be sent with this response, or empty
     // string to specify no mime type.
@@ skipping 14 matching lines @@
     // such requests more rapidly when there is a large amount of UI thread
     // contention.
     virtual MessageLoop* MessageLoopForRequestPath(const std::string& path)
         const;
 
     const std::string& source_name() const { return source_name_; }
 
     static void SetFontAndTextDirection(DictionaryValue* localized_strings);
 
    protected:
-    friend class base::RefCountedThreadSafe<DataSource>;
-    friend struct BrowserThread::DeleteOnThread<BrowserThread::UI>;
-    friend class DeleteTask<DataSource>;
-
     virtual ~DataSource();
 
    private:
+    friend class ChromeURLDataManagerBackend;
+    friend class ChromeURLDataManager;
+    friend class DeleteTask<DataSource>;
+
+    // SendResponse invokes this on the IO thread. Notifies the backend to
+    // handle the actual work of sending the data.
+    virtual void SendResponseOnIOThread(int request_id,
+                                        scoped_refptr<RefCountedMemory> bytes);
+
     // The name of this source.
     // E.g., for favicons, this could be "favicon", which results in paths for
     // specific resources like "favicon/34" getting sent to this source.
     const std::string source_name_;
 
     // The MessageLoop for the thread where this DataSource lives.
     // Used to send messages to the DataSource.
     MessageLoop* message_loop_;
+
+    // This field is set and maintained by ChromeURLDataManagerBackend. It is
+    // set when the DataSource is added, and unset if the DataSource is removed.
+    // A DataSource can be removed in two ways: the ChromeURLDataManagerBackend
+    // is deleted, or another DataSource is registered with the same
+    // name. backend_ should only be accessed on the IO thread.
+    // This reference can't be via a scoped_refptr else there would be a cycle
+    // between the backend and data source.
+    ChromeURLDataManagerBackend* backend_;
   };
 
-  // Add a DataSource to the collection of data sources.
-  // Because we don't track users of a given path, we can't know when it's
-  // safe to remove them, so the added source effectively leaks.
-  // This could be improved in the future but currently the users of this
-  // interface are conceptually permanent registration anyway.
-  // Adding a second DataSource with the same name clobbers the first.
-  // NOTE: Calling this from threads other the IO thread must be done via
-  // InvokeLater.
-  void AddDataSource(scoped_refptr<DataSource> source);
-  // Called during shutdown, before destruction of |BrowserThread|.
-  void RemoveDataSourceForTest(const char* source_name);  // For unit tests.
-  void RemoveAllDataSources();  // For the browser.
+  explicit ChromeURLDataManager(Profile* profile);
+  ~ChromeURLDataManager();
 
-  // Add/remove a path from the collection of file sources.
-  // A file source acts like a file:// URL to the specified path.
-  // Calling this from threads other the IO thread must be done via
-  // InvokeLater.
-  void AddFileSource(const std::string& source_name, const FilePath& path);
-  void RemoveFileSource(const std::string& source_name);
+  // Adds a DataSource to the collection of data sources. This *must* be invoked
+  // on the UI thread.
+  //
+  // If |AddDataSource| is called more than once for a particular name it will
+  // release the old |DataSource|, most likely resulting in it getting deleted
+  // as there are no other references to it. |DataSource| uses the
+  // |DeleteOnUIThread| trait to insure that the destructor is called on the UI
+  // thread. This is necessary as some |DataSource|s notably |FileIconSource|
+  // and |WebUIFavIconSource|, have members that will DCHECK if they are not
+  // destructed in the same thread as they are constructed (the UI thread).
+  void AddDataSource(DataSource* source);
 
-  static net::URLRequestJob* Factory(net::URLRequest* request,
-                                     const std::string& scheme);
+  // Deletes any data sources no longer referenced. This is normally invoked
+  // for you, but can be invoked to force deletion (such as during shutdown).
+  static void DeleteDataSources();
 
  private:
-  friend class URLRequestChromeJob;
-  friend struct DefaultSingletonTraits<ChromeURLDataManager>;
+  typedef std::vector<const ChromeURLDataManager::DataSource*> DataSources;
 
-  ChromeURLDataManager();
-  ~ChromeURLDataManager();
+  // If invoked on the UI thread the DataSource is deleted immediatlye,
+  // otherwise it is added to |data_sources_| and a task is scheduled to handle
+  // deletion on the UI thread. See note abouve DeleteDataSource for more info.
+  static void DeleteDataSource(const DataSource* data_source);
 
-  // Parse a URL into the components used to resolve its request.
-  static void URLToRequest(const GURL& url,
-                           std::string* source,
-                           std::string* path);
+  // Returns true if |data_source| is scheduled for deletion (|DeleteDataSource|
+  // was invoked).
+  static bool IsScheduledForDeletion(const DataSource* data_source);
 
-  // Translate a chrome resource URL into a local file path if there is one.
-  // Returns false if there is no file handler for this URL
-  static bool URLToFilePath(const GURL& url, FilePath* file_path);
+  Profile* profile_;
 
-  // Called by the job when it's starting up.
-  // Returns false if |url| is not a URL managed by this object.
-  bool StartRequest(const GURL& url, URLRequestChromeJob* job);
-  // Remove a request from the list of pending requests.
-  void RemoveRequest(URLRequestChromeJob* job);
+  // Lock used when accessing |data_sources_|.
+  static base::Lock delete_lock_;
 
-  // Returns true if the job exists in |pending_requests_|. False otherwise.
-  // Called by ~URLRequestChromeJob to verify that |pending_requests_| is kept
-  // up to date.
-  bool HasPendingJob(URLRequestChromeJob* job) const;
+  // |data_sources_| that are no longer referenced and scheduled for deletion.
+  static DataSources* data_sources_;
 
-  // Sent by Request::SendResponse.
-  void DataAvailable(RequestID request_id,
-                     scoped_refptr<RefCountedMemory> bytes);
-
-  // File sources of data, keyed by source name (e.g. "inspector").
-  typedef std::map<std::string, FilePath> FileSourceMap;
-  FileSourceMap file_sources_;
-
-  // Custom sources of data, keyed by source path (e.g. "favicon").
-  typedef std::map<std::string, scoped_refptr<DataSource> > DataSourceMap;
-  DataSourceMap data_sources_;
-
-  // All pending URLRequestChromeJobs, keyed by ID of the request.
-  // URLRequestChromeJob calls into this object when it's constructed and
-  // destructed to ensure that the pointers in this map remain valid.
-  typedef std::map<RequestID, URLRequestChromeJob*> PendingRequestMap;
-  PendingRequestMap pending_requests_;
-
-  // The ID we'll use for the next request we receive.
-  RequestID next_request_id_;
+  DISALLOW_COPY_AND_ASSIGN(ChromeURLDataManager);
 };
 
-// Since we have a single global ChromeURLDataManager, we don't need to
-// grab a reference to it when creating Tasks involving it.
-DISABLE_RUNNABLE_METHOD_REFCOUNT(ChromeURLDataManager);
-
-// Register our special URL handler under our special URL scheme.
-// Must be done once at startup.
-void RegisterURLRequestChromeJob();
-
-// Undoes the registration done by RegisterURLRequestChromeJob.
-void UnregisterURLRequestChromeJob();
-
 #endif  // CHROME_BROWSER_DOM_UI_CHROME_URL_DATA_MANAGER_H_