gecko/js/xpconnect/public/nsAutoJSValHolder.h

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/* -*- Mode: c++; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is worker threads.
*
* The Initial Developer of the Original Code is
* Mozilla Corporation.
* Portions created by the Initial Developer are Copyright (C) 2008
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Ben Turner <bent.mozilla@gmail.com> (Original Author)
* Ben Newman <b{enjamn,newman}@mozilla.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef __NSAUTOJSVALHOLDER_H__
#define __NSAUTOJSVALHOLDER_H__
#include "jsapi.h"
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#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(nsnull)
{
// nothing to do
}
/**
* Always release on destruction.
*/
virtual ~nsAutoJSValHolder() {
Release();
}
nsAutoJSValHolder(const nsAutoJSValHolder& aOther) {
*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 = nsnull;
}
if (!mRt && js_AddRootRT(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_RemoveRoot(mRt, &mVal); // infallible
mRt = nsnull;
}
mVal = JSVAL_NULL;
return oldval;
}
/**
* Determine if Hold has been called.
*/
bool IsHeld() const {
return !!mRt;
}
/**
* Explicit JSObject* conversion.
*/
JSObject* ToJSObject() const {
return JSVAL_IS_OBJECT(mVal)
? JSVAL_TO_OBJECT(mVal)
: nsnull;
}
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__ */