Fix a race condition in the Java Bridge when adding objects

content/browser/renderer_host/java/java_bridge_channel_host.h

 // 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 CONTENT_BROWSER_RENDERER_HOST_JAVA_JAVA_BRIDGE_CHANNEL_HOST_H_
 #define CONTENT_BROWSER_RENDERER_HOST_JAVA_JAVA_BRIDGE_CHANNEL_HOST_H_
 #pragma once
 
 #include "content/common/np_channel_base.h"
 
+// Threadsafe route ID generator.

[joth, 2011/12/07 14:49:09]

could you expand this a little:
- allows injection of the logic that will be used to create the route ID
- GenerateRouteID() must be [re-entrant | safe to call on any thread]

[Steve Block, 2011/12/07 16:47:44]

Done.

+class RouteIDGenerator : public base::RefCountedThreadSafe<RouteIDGenerator> {
+ public:
+  int GenerateRouteID() const;
+ private:

[joth, 2011/12/07 14:49:09]

\n before

+  friend class base::RefCountedThreadSafe<RouteIDGenerator>;
+  ~RouteIDGenerator() {}

[joth, 2011/12/07 14:49:09]

d'tor body always in .cc

+};

[joth, 2011/12/07 14:49:09]

as this does not have any state (other than in a static) would it be OK to pass
this as a plain-old function pointer, rather than create thread safe ref-counted
object for this?
Or even, just a plain function which both consumers can call directly (no need
for a function pointer?)

I'm not quite sure what the state is that this object instance captures.

[Steve Block, 2011/12/07 16:47:44]

The only state this captures is ensuring that all calls (for a given
JavaBridgeDispatcherHost) get a unique ID. I was considering using a different
series of IDs per JavaBridgeDispatcherHost, but you're right that if we use a
global series, this can be a static function.

+
 class JavaBridgeChannelHost : public NPChannelBase {
  public:
   static JavaBridgeChannelHost* GetJavaBridgeChannelHost(
-      int renderer_id, base::MessageLoopProxy*);
+      int renderer_id, base::MessageLoopProxy* ipc_message_loop,

[joth, 2011/12/07 14:49:09]

one param per line in declarations.

+      RouteIDGenerator* route_id_generator);
 
   // NPChannelBase implementation:
   virtual int GenerateRouteID() OVERRIDE;
 
   // NPChannelBase override:
   virtual bool Init(base::MessageLoopProxy* ipc_message_loop,
                     bool create_pipe_now,
                     base::WaitableEvent* shutdown_event) OVERRIDE;
   virtual bool Send(IPC::Message* msg) OVERRIDE;
 
  private:
   JavaBridgeChannelHost() {}
   friend class base::RefCountedThreadSafe<JavaBridgeChannelHost>;
   virtual ~JavaBridgeChannelHost() {}
 
   static NPChannelBase* ClassFactory() {
     return new JavaBridgeChannelHost();
   }
 
+  // Message handlers
+  void OnGenerateRouteID(int* route_id);
+
+  scoped_refptr<RouteIDGenerator> route_id_generator_;
+
   DISALLOW_COPY_AND_ASSIGN(JavaBridgeChannelHost);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_JAVA_JAVA_BRIDGE_CHANNEL_HOST_H_