dom/bindings/SpiderMonkeyInterface.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_dom_SpiderMonkeyInterface_h
   8 #define mozilla_dom_SpiderMonkeyInterface_h
   9
  10 #include "jsapi.h"
  11 #include "js/RootingAPI.h"
  12 #include "js/TracingAPI.h"
  13
  14 namespace mozilla {
  15 namespace dom {
  16
  17 /*
  18  * Class that just handles the JSObject storage and tracing for spidermonkey
  19  * interfaces
  20  */
  21 struct SpiderMonkeyInterfaceObjectStorage {
  22  protected:
  23   JSObject* mImplObj;
  24   JSObject* mWrappedObj;
  25
  26   SpiderMonkeyInterfaceObjectStorage()
  27       : mImplObj(nullptr), mWrappedObj(nullptr) {}
  28
  29   SpiderMonkeyInterfaceObjectStorage(
  30       SpiderMonkeyInterfaceObjectStorage&& aOther)
  31       : mImplObj(aOther.mImplObj), mWrappedObj(aOther.mWrappedObj) {
  32     aOther.mImplObj = nullptr;
  33     aOther.mWrappedObj = nullptr;
  34   }
  35
  36  public:
  37   inline void TraceSelf(JSTracer* trc) {
  38     JS::TraceRoot(trc, &mImplObj,
  39                   "SpiderMonkeyInterfaceObjectStorage.mImplObj");
  40     JS::TraceRoot(trc, &mWrappedObj,
  41                   "SpiderMonkeyInterfaceObjectStorage.mWrappedObj");
  42   }
  43
  44   inline bool inited() const { return !!mImplObj; }
  45
  46   inline bool WrapIntoNewCompartment(JSContext* cx) {
  47     return JS_WrapObject(
  48         cx, JS::MutableHandle<JSObject*>::fromMarkedLocation(&mWrappedObj));
  49   }
  50
  51   inline JSObject* Obj() const {
  52     MOZ_ASSERT(inited());
  53     return mWrappedObj;
  54   }
  55
  56  private:
  57   SpiderMonkeyInterfaceObjectStorage(
  58       const SpiderMonkeyInterfaceObjectStorage&) = delete;
  59 };
  60
  61 // A class for rooting an existing SpiderMonkey Interface struct
  62 template <typename InterfaceType>
  63 class MOZ_RAII SpiderMonkeyInterfaceRooter : private JS::CustomAutoRooter {
  64  public:
  65   template <typename CX>
  66   SpiderMonkeyInterfaceRooter(const CX& cx, InterfaceType* aInterface)
  67       : JS::CustomAutoRooter(cx), mInterface(aInterface) {}
  68
  69   virtual void trace(JSTracer* trc) override { mInterface->TraceSelf(trc); }
  70
  71  private:
  72   SpiderMonkeyInterfaceObjectStorage* const mInterface;
  73 };
  74
  75 // And a specialization for dealing with nullable SpiderMonkey interfaces
  76 template <typename Inner>
  77 struct Nullable;
  78 template <typename InterfaceType>
  79 class MOZ_RAII SpiderMonkeyInterfaceRooter<Nullable<InterfaceType>>
  80     : private JS::CustomAutoRooter {
  81  public:
  82   template <typename CX>
  83   SpiderMonkeyInterfaceRooter(const CX& cx, Nullable<InterfaceType>* aInterface)
  84       : JS::CustomAutoRooter(cx), mInterface(aInterface) {}
  85
  86   virtual void trace(JSTracer* trc) override {
  87     if (!mInterface->IsNull()) {
  88       mInterface->Value().TraceSelf(trc);
  89     }
  90   }
  91
  92  private:
  93   Nullable<InterfaceType>* const mInterface;
  94 };
  95
  96 // Class for easily setting up a rooted SpiderMonkey interface object on the
  97 // stack
  98 template <typename InterfaceType>
  99 class MOZ_RAII RootedSpiderMonkeyInterface final
 100     : public InterfaceType,
 101       private SpiderMonkeyInterfaceRooter<InterfaceType> {
 102  public:
 103   template <typename CX>
 104   explicit RootedSpiderMonkeyInterface(const CX& cx)
 105       : InterfaceType(), SpiderMonkeyInterfaceRooter<InterfaceType>(cx, this) {}
 106
 107   template <typename CX>
 108   RootedSpiderMonkeyInterface(const CX& cx, JSObject* obj)
 109       : InterfaceType(obj),
 110         SpiderMonkeyInterfaceRooter<InterfaceType>(cx, this) {}
 111 };
 112
 113 }  // namespace dom
 114 }  // namespace mozilla
 115
 116 #endif /* mozilla_dom_SpiderMonkeyInterface_h */