chrome/renderer/extensions/unsafe_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_UNSAFE_PERSISTENT_H_
   6 #define CHROME_RENDERER_EXTENSIONS_UNSAFE_PERSISTENT_H_
   7
   8 #include "v8/include/v8.h"
   9
  10 namespace extensions {
  11
  12 // An unsafe way to pass Persistent handles around. Do not use unless you know
  13 // what you're doing. UnsafePersistent is only safe to use when we know that the
  14 // memory pointed by it is not going away: 1) When GC cannot happen while the
  15 // UnsafePersistent is alive or 2) when there is a strong Persistent keeping the
  16 // memory alive while the UnsafePersistent is alive.
  17 template<typename T> class UnsafePersistent {
  18  public:
  19   UnsafePersistent() : value_(0) { }
  20
  21   explicit UnsafePersistent(v8::Persistent<T>* handle) {
  22     value_ = handle->ClearAndLeak();
  23   }
  24
  25   UnsafePersistent(v8::Isolate* isolate, const v8::Handle<T>& handle) {
  26     v8::Persistent<T> persistent(isolate, handle);
  27     value_ = persistent.ClearAndLeak();
  28   }
  29
  30   // Usage of this function requires
  31   // V8_ALLOW_ACCESS_TO_RAW_HANDLE_CONSTRUCTOR to be defined
  32   void dispose() {
  33     v8::Persistent<T> handle(value_);
  34     handle.Reset();
  35     value_ = 0;
  36   }
  37
  38   // Usage of this function requires
  39   // V8_ALLOW_ACCESS_TO_RAW_HANDLE_CONSTRUCTOR to be defined
  40   v8::Local<T> newLocal(v8::Isolate* isolate) {
  41     return v8::Local<T>::New(isolate, v8::Local<T>(value_));
  42   }
  43
  44  private:
  45   T* value_;
  46 };
  47
  48 }  // namespace extensions
  49
  50 #endif  // CHROME_RENDERER_EXTENSIONS_UNSAFE_PERSISTENT_H_