gecko-dev/js/xpconnect/public/nsAutoJSValHolder.h

141 lines
2.8 KiB
C++

/* -*- Mode: c++; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef __NSAUTOJSVALHOLDER_H__
#define __NSAUTOJSVALHOLDER_H__
#include "jsapi.h"
#include "nsDebug.h"
/**
* Simple class that looks and acts like a jsval except that it unroots
* itself automatically if Root() is ever called. Designed to be rooted on the
* context or runtime (but not both!).
*/
class nsAutoJSValHolder
{
public:
nsAutoJSValHolder()
: mVal(JSVAL_NULL), mRt(nullptr)
{
// nothing to do
}
/**
* Always release on destruction.
*/
virtual ~nsAutoJSValHolder() {
Release();
}
nsAutoJSValHolder(const nsAutoJSValHolder& aOther)
: mVal(JSVAL_NULL), mRt(nullptr)
{
*this = aOther;
}
nsAutoJSValHolder& operator=(const nsAutoJSValHolder& aOther) {
if (this != &aOther) {
if (aOther.IsHeld()) {
// XXX No error handling here...
this->Hold(aOther.mRt);
}
else {
this->Release();
}
*this = static_cast<jsval>(aOther);
}
return *this;
}
/**
* Hold by rooting on the context's runtime.
*/
bool Hold(JSContext* aCx) {
return Hold(JS_GetRuntime(aCx));
}
/**
* Hold by rooting on the runtime.
* Note that mVal may be JSVAL_NULL, which is not a problem.
*/
bool Hold(JSRuntime* aRt) {
// Do we really care about different runtimes?
if (mRt && aRt != mRt) {
js_RemoveRoot(mRt, &mVal);
mRt = nullptr;
}
if (!mRt && JS_AddNamedValueRootRT(aRt, &mVal, "nsAutoJSValHolder")) {
mRt = aRt;
}
return !!mRt;
}
/**
* Manually release, nullifying mVal, and mRt, but returning
* the original jsval.
*/
jsval Release() {
jsval oldval = mVal;
if (mRt) {
JS_RemoveValueRootRT(mRt, &mVal); // infallible
mRt = nullptr;
}
mVal = JSVAL_NULL;
return oldval;
}
/**
* Determine if Hold has been called.
*/
bool IsHeld() const {
return !!mRt;
}
/**
* Explicit JSObject* conversion.
*/
JSObject* ToJSObject() const {
return mVal.isObject()
? &mVal.toObject()
: nullptr;
}
jsval* ToJSValPtr() {
return &mVal;
}
/**
* Pretend to be a jsval.
*/
operator jsval() const { return mVal; }
nsAutoJSValHolder &operator=(JSObject* aOther) {
return *this = OBJECT_TO_JSVAL(aOther);
}
nsAutoJSValHolder &operator=(jsval aOther) {
#ifdef DEBUG
if (JSVAL_IS_GCTHING(aOther) && !JSVAL_IS_NULL(aOther)) {
NS_ASSERTION(IsHeld(), "Not rooted!");
}
#endif
mVal = aOther;
return *this;
}
private:
jsval mVal;
JSRuntime* mRt;
};
#endif /* __NSAUTOJSVALHOLDER_H__ */