Splits ChromeURLDataManager into 2 chunks:...

chrome/browser/dom_ui/chrome_url_data_manager_backend.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_
+#ifndef CHROME_BROWSER_DOM_UI_CHROME_URL_DATA_MANAGER_BACKEND_H_
+#define CHROME_BROWSER_DOM_UI_CHROME_URL_DATA_MANAGER_BACKEND_H_
 #pragma once
 
+#include "base/basictypes.h"
+#include "base/ref_counted.h"
+#include "base/synchronization/lock.h"
+#include "chrome/browser/dom_ui/chrome_url_data_manager.h"
+
 #include <map>
 #include <string>
+#include <vector>
 
-#include "base/singleton.h"
-#include "base/task.h"
-#include "base/ref_counted.h"
-#include "chrome/browser/browser_thread.h"
-
-class DictionaryValue;
 class FilePath;
 class GURL;
-class MessageLoop;
-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.
-class ChromeURLDataManager {
+// ChromeURLDataManagerBackend is used internally by ChromeURLDataManager (and
+// during shutdown). In most cases you can use the API in ChromeURLDataManager
+// and ignore this class.
+//
+// ChromeURLDataManagerBackend stores the DataSources and is responsible for
+// mapping URLRequests to DataSources. ChromeURLDataManagerBackend is used on
+// the IO thread (except during shutdown). ChromeURLDataManager ensures
+// ChromeURLDataManagerBackend is used on the IO thread.
+class ChromeURLDataManagerBackend
+    : public base::RefCountedThreadSafe<ChromeURLDataManagerBackend> {
  public:
-  // Returns the singleton instance.
-  static ChromeURLDataManager* GetInstance();
-
   typedef int RequestID;
 
-  // 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.
-  //
-  // 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> {
-   public:
-    // See source_name_ and message_loop_ below for docs on these parameters.
-    DataSource(const std::string& source_name,
-               MessageLoop* message_loop);
+  ChromeURLDataManagerBackend();
 
-    // 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;
+  // Invoked to register the protocol factories. This must be invoked at startup
+  // before ChromeURLDataManagerBackend is used and before the IO thread
+  // attempts to use it.
+  static void Register();
 
-    // Return the mimetype that should be sent with this response, or empty
-    // string to specify no mime type.
-    virtual std::string GetMimeType(const std::string& path) const = 0;
+  // Invoked on the UI thread prior to shutdown.
+  static void PrepareForShutdown();
 
-    // Report that a request has resulted in the data |bytes|.
-    // If the request can't be satisfied, pass NULL for |bytes| to indicate
-    // the request is over.
-    virtual void SendResponse(int request_id, RefCountedMemory* bytes);
+  // Finishes shutdown so that the none of the existing
+  // ChromeURLDataManagerBackends reference any DataSources. This is invoked on
+  // the UI thread so that the DataSources can be destroyed on the UI thread.
+  static void CompleteShutdown();
 
-    // Returns the MessageLoop on which the DataSource wishes to have
-    // StartDataRequest called to handle the request for |path|.  If the
-    // DataSource does not care which thread StartDataRequest is called on,
-    // this should return NULL.  The default implementation always returns
-    // message_loop_, which generally results in processing on the UI thread.
-    // It may be beneficial to return NULL for requests that are safe to handle
-    // directly on the IO thread.  This can improve performance by satisfying
-    // 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:
-    // 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_;
-  };
-
-  // 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.
+  // Adds a DataSource to the collection of data sources.
+  void AddDataSource(ChromeURLDataManager::DataSource* source);
 
   // 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);
+
+  // DataSource invokes this. Sends the data to the URLRequest.
+  void DataAvailable(RequestID request_id, RefCountedMemory* bytes);
 
   static net::URLRequestJob* Factory(net::URLRequest* request,
                                      const std::string& scheme);
 
  private:
+  friend class base::RefCountedThreadSafe<ChromeURLDataManagerBackend>;
   friend class URLRequestChromeJob;
-  friend struct DefaultSingletonTraits<ChromeURLDataManager>;
 
-  ChromeURLDataManager();
-  ~ChromeURLDataManager();
+  typedef std::map<std::string,
+      scoped_refptr<ChromeURLDataManager::DataSource> > DataSourceMap;
+  typedef std::map<std::string, FilePath> FileSourceMap;
+  typedef std::map<RequestID, URLRequestChromeJob*> PendingRequestMap;
+  typedef std::vector<ChromeURLDataManagerBackend*> Instances;
+  typedef std::vector<scoped_refptr<ChromeURLDataManagerBackend> >
+      LockedInstances;
+
+  ~ChromeURLDataManagerBackend();
 
   // Parse a URL into the components used to resolve its request.
-  static void URLToRequest(const GURL& url,
-                           std::string* source,
-                           std::string* path);
+  void URLToRequest(const GURL& url, std::string* source, std::string* path);
 
   // 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);
+  bool URLToFilePath(const GURL& url, FilePath* file_path);
 
   // 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);
 
   // 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;
 
-  // Sent by Request::SendResponse.
-  void DataAvailable(RequestID request_id,
-                     scoped_refptr<RefCountedMemory> bytes);
+  // Resets the |backend_| of each DataSource and clears out |data_sources_|.
+  // This may be invoked on any thread.
+  void ReleaseDataSources();
 
   // 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;
+  // WARNING: this may be accessed from the IO or UI threads. Access must be
+  // guarded by |data_sources_lock_|.
   DataSourceMap data_sources_;
 
+  // Lock used to access data sources.
+  base::Lock data_sources_lock_;
+
   // 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_;
+
+  // Lock used to access |instances_| and |shutdown_instances_|.
+  static base::Lock* instances_lock_;
+
+  // ChromeURLDataManagerBackend instances. All access must be done with
+  // |instance_lock_| held. See comment in PrepareForShutdown for details.
+  static Instances* instances_;
+
+  // If non-null, we're in the process of shuting down. See comment in
+  // PrepareForShutdown for details.
+  static LockedInstances* shutdown_instances_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeURLDataManagerBackend);
 };
 
-// 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_
+#endif  // CHROME_BROWSER_DOM_UI_CHROME_URL_DATA_MANAGER_BACKEND_H_