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