dom/src/threads/nsAutoJSObjectHolder.h

   1 /* -*- Mode: c++; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*- */
   2 /* ***** BEGIN LICENSE BLOCK *****
   3  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   4  *
   5  * The contents of this file are subject to the Mozilla Public License Version
   6  * 1.1 (the "License"); you may not use this file except in compliance with
   7  * the License. You may obtain a copy of the License at
   8  * http://www.mozilla.org/MPL/
   9  *
  10  * Software distributed under the License is distributed on an "AS IS" basis,
  11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  12  * for the specific language governing rights and limitations under the
  13  * License.
  14  *
  15  * The Original Code is worker threads.
  16  *
  17  * The Initial Developer of the Original Code is
  18  *   Mozilla Corporation.
  19  * Portions created by the Initial Developer are Copyright (C) 2008
  20  * the Initial Developer. All Rights Reserved.
  21  *
  22  * Contributor(s):
  23  *   Ben Turner <bent.mozilla@gmail.com> (Original Author)
  24  *
  25  * Alternatively, the contents of this file may be used under the terms of
  26  * either the GNU General Public License Version 2 or later (the "GPL"), or
  27  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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  36  *
  37  * ***** END LICENSE BLOCK ***** */
  38
  39 #ifndef __NSAUTOJSOBJECTHOLDER_H__
  40 #define __NSAUTOJSOBJECTHOLDER_H__
  41
  42 #include "jsapi.h"
  43
  44 /**
  45  * Simple class that looks and acts like a JSObject* except that it unroots
  46  * itself automatically if Root() is ever called. Designed to be rooted on the
  47  * context or runtime (but not both!). Also automatically nulls its JSObject*
  48  * on Unroot and asserts that Root has been called prior to assigning an object.
  49  */
  50 class nsAutoJSObjectHolder
  51 {
  52 public:
  53   /**
  54    * Default constructor, no holding.
  55    */
  56   nsAutoJSObjectHolder()
  57   : mRt(NULL), mObj(NULL), mHeld(PR_FALSE) { }
  58
  59   /**
  60    * Hold by rooting on the context's runtime in the constructor, passing the
  61    * result out.
  62    */
  63   nsAutoJSObjectHolder(JSContext* aCx, JSBool* aRv = NULL,
  64                        JSObject* aObj = NULL)
  65   : mRt(NULL), mObj(aObj), mHeld(JS_FALSE) {
  66     JSBool rv = Hold(aCx);
  67     if (aRv) {
  68       *aRv = rv;
  69     }
  70   }
  71
  72   /**
  73    * Hold by rooting on the runtime in the constructor, passing the result out.
  74    */
  75   nsAutoJSObjectHolder(JSRuntime* aRt, JSBool* aRv = NULL,
  76                        JSObject* aObj = NULL)
  77   : mRt(aRt), mObj(aObj), mHeld(JS_FALSE) {
  78     JSBool rv = Hold(aRt);
  79     if (aRv) {
  80       *aRv = rv;
  81     }
  82   }
  83
  84   /**
  85    * Always release on destruction.
  86    */
  87   ~nsAutoJSObjectHolder() {
  88     Release();
  89   }
  90
  91   /**
  92    * Hold by rooting on the context's runtime.
  93    */
  94   JSBool Hold(JSContext* aCx) {
  95     return Hold(JS_GetRuntime(aCx));
  96   }
  97
  98   /**
  99    * Hold by rooting on the runtime.
 100    */
 101   JSBool Hold(JSRuntime* aRt) {
 102     if (!mHeld) {
 103       mHeld = JS_AddNamedRootRT(aRt, &mObj, "nsAutoRootedJSObject");
 104       if (mHeld) {
 105         mRt = aRt;
 106       }
 107     }
 108     return mHeld;
 109   }
 110
 111   /**
 112    * Manually release.
 113    */
 114   void Release() {
 115     NS_ASSERTION(!mHeld || mRt, "Bad!");
 116     if (mHeld) {
 117       mHeld = !JS_RemoveRootRT(mRt, &mObj);
 118       if (!mHeld) {
 119         mRt = NULL;
 120       }
 121       mObj = NULL;
 122     }
 123   }
 124
 125   /**
 126    * Determine if Hold has been called.
 127    */
 128   JSBool IsHeld() {
 129     return mHeld;
 130   }
 131
 132   /**
 133    * Pretend to be a JSObject*.
 134    */
 135   JSObject* get() const {
 136     return mObj;
 137   }
 138
 139   /**
 140    * Pretend to be a JSObject*.
 141    */
 142   operator JSObject*() const {
 143     return get();
 144   }
 145
 146   /**
 147    * Pretend to be a JSObject*. Assert if not held.
 148    */
 149   JSObject* operator=(JSObject* aOther) {
 150     NS_ASSERTION(mHeld, "Not rooted!");
 151     return mObj = aOther;
 152   }
 153
 154 private:
 155   JSRuntime* mRt;
 156   JSObject* mObj;
 157   JSBool mHeld;
 158 };
 159
 160 #endif /* __NSAUTOJSOBJECTHOLDER_H__ */