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     handle_.Reset(GetIsolate(handle), handle);
  31   }
  32
  33   void reset() {
  34     if (handle_.IsEmpty())
  35       return;
  36     handle_.Dispose(GetIsolate(handle_));
  37     handle_.Clear();
  38   }
  39
  40   v8::Persistent<T> operator->() const {
  41     return handle_;
  42   }
  43
  44   v8::Persistent<T> get() const {
  45     return handle_;
  46   }
  47
  48   void MakeWeak(void* parameters, v8::NearDeathCallback callback) {
  49     handle_.MakeWeak(GetIsolate(handle_), parameters, callback);
  50   }
  51
  52  private:
  53   template <typename U>
  54   static v8::Isolate* GetIsolate(v8::Handle<U> object_handle) {
  55     // Only works for v8::Object and its subclasses. Add specialisations for
  56     // anything else.
  57     return GetIsolate(object_handle->CreationContext());
  58   }
  59   static v8::Isolate* GetIsolate(v8::Handle<v8::Context> context_handle) {
  60     return context_handle->GetIsolate();
  61   }
  62   static v8::Isolate* GetIsolate(
  63       v8::Handle<v8::ObjectTemplate> template_handle) {
  64     return v8::Isolate::GetCurrent();
  65   }
  66
  67   v8::Persistent<T> handle_;
  68
  69   DISALLOW_COPY_AND_ASSIGN(ScopedPersistent);
  70 };
  71
  72 }  // namespace extensions
  73
  74 #endif  // CHROME_RENDERER_EXTENSIONS_SCOPED_PERSISTENT_H_