chrome/renderer/extensions/scoped_persistent.h

   1 // Copyright 2013 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 CHROME_RENDERER_EXTENSIONS_SCOPED_PERSISTENT_H_
   6 #define CHROME_RENDERER_EXTENSIONS_SCOPED_PERSISTENT_H_
   7
   8 #include "base/logging.h"
   9 #include "v8/include/v8.h"
  10
  11 namespace extensions {
  12
  13 // A v8::Persistent handle to a V8 value which destroys and clears the
  14 // underlying handle on destruction.
  15 template <typename T>
  16 class ScopedPersistent {
  17  public:
  18   ScopedPersistent() {
  19   }
  20
  21   explicit ScopedPersistent(v8::Handle<T> handle) {
  22     reset(handle);
  23   }
  24
  25   ~ScopedPersistent() {
  26     reset();
  27   }
  28
  29   void reset(v8::Handle<T> handle) {
  30     if (!handle.IsEmpty())
  31       handle_.Reset(GetIsolate(handle), handle);
  32     else
  33       reset();
  34   }
  35
  36   void reset() {
  37     handle_.Reset();
  38   }
  39
  40   bool IsEmpty() const {
  41     return handle_.IsEmpty();
  42   }
  43
  44   v8::Handle<T> NewHandle() const {
  45     if (handle_.IsEmpty())
  46       return v8::Local<T>();
  47     return v8::Local<T>::New(GetIsolate(handle_), handle_);
  48   }
  49
  50   v8::Handle<T> NewHandle(v8::Isolate* isolate) const {
  51     if (handle_.IsEmpty())
  52       return v8::Local<T>();
  53     return v8::Local<T>::New(isolate, handle_);
  54   }
  55
  56   template <typename P>
  57   void SetWeak(P* parameters,
  58                typename v8::WeakCallbackData<T, P>::Callback callback) {
  59     handle_.SetWeak(parameters, callback);
  60   }
  61
  62  private:
  63   template <typename U>
  64   static v8::Isolate* GetIsolate(v8::Handle<U> object_handle) {
  65     // Only works for v8::Object and its subclasses. Add specialisations for
  66     // anything else.
  67     if (!object_handle.IsEmpty())
  68       return GetIsolate(object_handle->CreationContext());
  69     return v8::Isolate::GetCurrent();
  70   }
  71   static v8::Isolate* GetIsolate(v8::Handle<v8::Context> context_handle) {
  72     if (!context_handle.IsEmpty())
  73       return context_handle->GetIsolate();
  74     return v8::Isolate::GetCurrent();
  75   }
  76   static v8::Isolate* GetIsolate(
  77       v8::Handle<v8::ObjectTemplate> template_handle) {
  78     return v8::Isolate::GetCurrent();
  79   }
  80
  81   v8::Persistent<T> handle_;
  82
  83   DISALLOW_COPY_AND_ASSIGN(ScopedPersistent);
  84 };
  85
  86 }  // namespace extensions
  87
  88 #endif  // CHROME_RENDERER_EXTENSIONS_SCOPED_PERSISTENT_H_