extensions/renderer/scoped_persistent.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_SCOPED_PERSISTENT_H_
   6 #define EXTENSIONS_RENDERER_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   explicit ScopedPersistent(v8::Handle<T> handle) { reset(handle); }
  21
  22   ScopedPersistent(v8::Isolate* isolate, v8::Handle<T> handle) {
  23     reset(isolate, handle);
  24   }
  25
  26   ~ScopedPersistent() { reset(); }
  27
  28   void reset(v8::Isolate* isolate, v8::Handle<T> handle) {
  29     if (!handle.IsEmpty())
  30       handle_.Reset(isolate, handle);
  31     else
  32       reset();
  33   }
  34
  35   void reset(v8::Handle<T> handle) { reset(GetIsolate(handle), handle); }
  36
  37   void reset() { handle_.Reset(); }
  38
  39   bool IsEmpty() const { return handle_.IsEmpty(); }
  40
  41   v8::Handle<T> NewHandle() const {
  42     if (handle_.IsEmpty())
  43       return v8::Local<T>();
  44     return v8::Local<T>::New(GetIsolate(handle_), handle_);
  45   }
  46
  47   v8::Handle<T> NewHandle(v8::Isolate* isolate) const {
  48     if (handle_.IsEmpty())
  49       return v8::Local<T>();
  50     return v8::Local<T>::New(isolate, handle_);
  51   }
  52
  53   template <typename P>
  54   void SetWeak(P* parameters,
  55                typename v8::WeakCallbackData<T, P>::Callback callback) {
  56     handle_.SetWeak(parameters, callback);
  57   }
  58
  59  private:
  60   template <typename U>
  61   static v8::Isolate* GetIsolate(v8::Handle<U> object_handle) {
  62     // Only works for v8::Object and its subclasses. Add specialisations for
  63     // anything else.
  64     if (!object_handle.IsEmpty())
  65       return GetIsolate(object_handle->CreationContext());
  66     return v8::Isolate::GetCurrent();
  67   }
  68   static v8::Isolate* GetIsolate(v8::Handle<v8::Context> context_handle) {
  69     if (!context_handle.IsEmpty())
  70       return context_handle->GetIsolate();
  71     return v8::Isolate::GetCurrent();
  72   }
  73   static v8::Isolate* GetIsolate(
  74       v8::Handle<v8::ObjectTemplate> template_handle) {
  75     return v8::Isolate::GetCurrent();
  76   }
  77
  78   v8::Persistent<T> handle_;
  79
  80   DISALLOW_COPY_AND_ASSIGN(ScopedPersistent);
  81 };
  82
  83 }  // namespace extensions
  84
  85 #endif  // EXTENSIONS_RENDERER_SCOPED_PERSISTENT_H_