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 "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   ~ObjectBackedNativeHandler() override;
  28
  29   // Create an object with bindings to the native functions defined through
  30   // RouteFunction().
  31   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   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_