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      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 EXTENSIONS_RENDERER_OBJECT_BACKED_NATIVE_HANDLER_H_
      6 #define EXTENSIONS_RENDERER_OBJECT_BACKED_NATIVE_HANDLER_H_
      7 
      8 #include <string>
      9 #include <vector>
     10 
     11 #include "base/bind.h"
     12 #include "base/memory/linked_ptr.h"
     13 #include "extensions/renderer/native_handler.h"
     14 #include "extensions/renderer/scoped_persistent.h"
     15 #include "v8/include/v8-util.h"
     16 #include "v8/include/v8.h"
     17 
     18 namespace extensions {
     19 class ScriptContext;
     20 
     21 // An ObjectBackedNativeHandler is a factory for JS objects with functions on
     22 // them that map to native C++ functions. Subclasses should call RouteFunction()
     23 // in their constructor to define functions on the created JS objects.
     24 class ObjectBackedNativeHandler : public NativeHandler {
     25  public:
     26   explicit ObjectBackedNativeHandler(ScriptContext* context);
     27   virtual ~ObjectBackedNativeHandler();
     28 
     29   // Create an object with bindings to the native functions defined through
     30   // RouteFunction().
     31   virtual v8::Handle<v8::Object> NewInstance() OVERRIDE;
     32 
     33   v8::Isolate* GetIsolate() const;
     34 
     35  protected:
     36   typedef base::Callback<void(const v8::FunctionCallbackInfo<v8::Value>&)>
     37       HandlerFunction;
     38 
     39   // Installs a new 'route' from |name| to |handler_function|. This means that
     40   // NewInstance()s of this ObjectBackedNativeHandler will have a property
     41   // |name| which will be handled by |handler_function|.
     42   void RouteFunction(const std::string& name,
     43                      const HandlerFunction& handler_function);
     44 
     45   ScriptContext* context() const { return context_; }
     46 
     47   virtual void Invalidate() OVERRIDE;
     48 
     49  private:
     50   // Callback for RouteFunction which routes the V8 call to the correct
     51   // base::Bound callback.
     52   static void Router(const v8::FunctionCallbackInfo<v8::Value>& args);
     53 
     54   // When RouteFunction is called we create a v8::Object to hold the data we
     55   // need when handling it in Router() - this is the base::Bound function to
     56   // route to.
     57   //
     58   // We need a v8::Object because it's possible for v8 to outlive the
     59   // base::Bound function; the lifetime of an ObjectBackedNativeHandler is the
     60   // lifetime of webkit's involvement with it, not the life of the v8 context.
     61   // A scenario when v8 will outlive us is if a frame holds onto the
     62   // contentWindow of an iframe after it's removed.
     63   //
     64   // So, we use v8::Objects here to hold that data, effectively refcounting
     65   // the data. When |this| is destroyed we remove the base::Bound function from
     66   // the object to indicate that it shoudn't be called.
     67   typedef v8::PersistentValueVector<v8::Object> RouterData;
     68   RouterData router_data_;
     69 
     70   ScriptContext* context_;
     71 
     72   ScopedPersistent<v8::ObjectTemplate> object_template_;
     73 
     74   DISALLOW_COPY_AND_ASSIGN(ObjectBackedNativeHandler);
     75 };
     76 
     77 }  // namespace extensions
     78 
     79 #endif  // EXTENSIONS_RENDERER_OBJECT_BACKED_NATIVE_HANDLER_H_
     80