extensions/renderer/object_backed_native_handler.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 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 "v8/include/v8-util.h"
  15 #include "v8/include/v8.h"
  16
  17 namespace extensions {
  18 class ScriptContext;
  19
  20 // An ObjectBackedNativeHandler is a factory for JS objects with functions on
  21 // them that map to native C++ functions. Subclasses should call RouteFunction()
  22 // in their constructor to define functions on the created JS objects.
  23 class ObjectBackedNativeHandler : public NativeHandler {
  24  public:
  25   explicit ObjectBackedNativeHandler(ScriptContext* context);
  26   ~ObjectBackedNativeHandler() override;
  27
  28   // Create an object with bindings to the native functions defined through
  29   // RouteFunction().
  30   v8::Local<v8::Object> NewInstance() override;
  31
  32   v8::Isolate* GetIsolate() const;
  33
  34  protected:
  35   typedef base::Callback<void(const v8::FunctionCallbackInfo<v8::Value>&)>
  36       HandlerFunction;
  37
  38   // Installs a new 'route' from |name| to |handler_function|. This means that
  39   // NewInstance()s of this ObjectBackedNativeHandler will have a property
  40   // |name| which will be handled by |handler_function|.
  41   //
  42   // Routed functions are destroyed along with the destruction of this class,
  43   // and are never called back into, therefore it's safe for |handler_function|
  44   // to bind to base::Unretained.
  45   void RouteFunction(const std::string& name,
  46                      const HandlerFunction& handler_function);
  47
  48   ScriptContext* context() const { return context_; }
  49
  50   void Invalidate() override;
  51
  52  private:
  53   // Callback for RouteFunction which routes the V8 call to the correct
  54   // base::Bound callback.
  55   static void Router(const v8::FunctionCallbackInfo<v8::Value>& args);
  56
  57   // When RouteFunction is called we create a v8::Object to hold the data we
  58   // need when handling it in Router() - this is the base::Bound function to
  59   // route to.
  60   //
  61   // We need a v8::Object because it's possible for v8 to outlive the
  62   // base::Bound function; the lifetime of an ObjectBackedNativeHandler is the
  63   // lifetime of webkit's involvement with it, not the life of the v8 context.
  64   // A scenario when v8 will outlive us is if a frame holds onto the
  65   // contentWindow of an iframe after it's removed.
  66   //
  67   // So, we use v8::Objects here to hold that data, effectively refcounting
  68   // the data. When |this| is destroyed we remove the base::Bound function from
  69   // the object to indicate that it shoudn't be called.
  70   typedef v8::PersistentValueVector<v8::Object> RouterData;
  71   RouterData router_data_;
  72
  73   ScriptContext* context_;
  74
  75   v8::Global<v8::ObjectTemplate> object_template_;
  76
  77   DISALLOW_COPY_AND_ASSIGN(ObjectBackedNativeHandler);
  78 };
  79
  80 }  // namespace extensions
  81
  82 #endif  // EXTENSIONS_RENDERER_OBJECT_BACKED_NATIVE_HANDLER_H_