michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim: set ts=8 sts=2 et sw=2 tw=80: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef __NSAUTOJSVALHOLDER_H__
michael@0: #define __NSAUTOJSVALHOLDER_H__
michael@0: 
michael@0: #include "nsDebug.h"
michael@0: #include "jsapi.h"
michael@0: 
michael@0: /**
michael@0:  * Simple class that looks and acts like a JS::Value except that it unroots
michael@0:  * itself automatically if Root() is ever called. Designed to be rooted on the
michael@0:  * context or runtime (but not both!).
michael@0:  */
michael@0: class nsAutoJSValHolder
michael@0: {
michael@0: public:
michael@0:   nsAutoJSValHolder()
michael@0:     : mVal(JSVAL_NULL), mRt(nullptr)
michael@0:   {
michael@0:     // nothing to do
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Always release on destruction.
michael@0:    */
michael@0:   virtual ~nsAutoJSValHolder() {
michael@0:     Release();
michael@0:   }
michael@0: 
michael@0:   nsAutoJSValHolder(const nsAutoJSValHolder& aOther)
michael@0:     : mVal(JSVAL_NULL), mRt(nullptr)
michael@0:   {
michael@0:     *this = aOther;
michael@0:   }
michael@0: 
michael@0:   nsAutoJSValHolder& operator=(const nsAutoJSValHolder& aOther) {
michael@0:     if (this != &aOther) {
michael@0:       if (aOther.IsHeld()) {
michael@0:         // XXX No error handling here...
michael@0:         this->Hold(aOther.mRt);
michael@0:       }
michael@0:       else {
michael@0:         this->Release();
michael@0:       }
michael@0:       *this = static_cast<JS::Value>(aOther);
michael@0:     }
michael@0:     return *this;
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Hold by rooting on the context's runtime.
michael@0:    */
michael@0:   bool Hold(JSContext* aCx) {
michael@0:     return Hold(JS_GetRuntime(aCx));
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Hold by rooting on the runtime.
michael@0:    * Note that mVal may be JSVAL_NULL, which is not a problem.
michael@0:    */
michael@0:   bool Hold(JSRuntime* aRt) {
michael@0:     MOZ_ASSERT_IF(mRt, mRt == aRt);
michael@0: 
michael@0:     if (!mRt && JS::AddNamedValueRootRT(aRt, &mVal, "nsAutoJSValHolder")) {
michael@0:       mRt = aRt;
michael@0:     }
michael@0: 
michael@0:     return !!mRt;
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Manually release, nullifying mVal, and mRt, but returning
michael@0:    * the original JS::Value.
michael@0:    */
michael@0:   JS::Value Release() {
michael@0:     JS::Value oldval = mVal;
michael@0: 
michael@0:     if (mRt) {
michael@0:       JS::RemoveValueRootRT(mRt, &mVal); // infallible
michael@0:       mRt = nullptr;
michael@0:     }
michael@0: 
michael@0:     mVal = JSVAL_NULL;
michael@0: 
michael@0:     return oldval;
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Determine if Hold has been called.
michael@0:    */
michael@0:   bool IsHeld() const {
michael@0:     return !!mRt;
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Explicit JSObject* conversion.
michael@0:    */
michael@0:   JSObject* ToJSObject() const {
michael@0:     return mVal.isObject()
michael@0:          ? &mVal.toObject()
michael@0:          : nullptr;
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Pretend to be a JS::Value.
michael@0:    */
michael@0:   operator JS::Value() const { return mVal; }
michael@0:   JS::Value get() const { return mVal; }
michael@0: 
michael@0:   nsAutoJSValHolder &operator=(JSObject* aOther) {
michael@0:     return *this = OBJECT_TO_JSVAL(aOther);
michael@0:   }
michael@0: 
michael@0:   nsAutoJSValHolder &operator=(JS::Value aOther) {
michael@0: #ifdef DEBUG
michael@0:     if (JSVAL_IS_GCTHING(aOther) && !JSVAL_IS_NULL(aOther)) {
michael@0:       MOZ_ASSERT(IsHeld(), "Not rooted!");
michael@0:     }
michael@0: #endif
michael@0:     mVal = aOther;
michael@0:     return *this;
michael@0:   }
michael@0: 
michael@0: private:
michael@0:   JS::Heap<JS::Value> mVal;
michael@0:   JSRuntime* mRt;
michael@0: };
michael@0: 
michael@0: #endif /* __NSAUTOJSVALHOLDER_H__ */