dom/base/nsWrapperCache.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   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 Gecko DOM code.
  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  *    Peter Van der Beken <peterv@propagandism.org>
  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"),
  28  * in which case the provisions of the GPL or the LGPL are applicable instead
  29  * of those above. If you wish to allow use of your version of this file only
  30  * under the terms of either the GPL or the LGPL, and not to allow others to
  31  * use your version of this file under the terms of the MPL, indicate your
  32  * decision by deleting the provisions above and replace them with the notice
  33  * and other provisions required by the GPL or the LGPL. If you do not delete
  34  * the provisions above, a recipient may use your version of this file under
  35  * the terms of any one of the MPL, the GPL or the LGPL.
  36  *
  37  * ***** END LICENSE BLOCK ***** */
  38
  39 #ifndef nsWrapperCache_h___
  40 #define nsWrapperCache_h___
  41
  42 #include "nsCycleCollectionParticipant.h"
  43
  44 struct JSObject;
  45
  46 typedef PRUptrdiff PtrBits;
  47
  48 #define NS_WRAPPERCACHE_IID \
  49 { 0x3a51ca81, 0xddab, 0x422c, \
  50   { 0x95, 0x3a, 0x13, 0x06, 0x28, 0x0e, 0xee, 0x14 } }
  51
  52 /**
  53  * Class to store the XPCWrappedNative for an object. This can only be used
  54  * with objects that only have one XPCWrappedNative at a time (usually ensured
  55  * by setting an explicit parent in the PreCreate hook for the class). This
  56  * object can be gotten by calling QueryInterface, note that this breaks XPCOM
  57  * rules a bit (this object doesn't derive from nsISupports).
  58  */
  59 class nsWrapperCache
  60 {
  61 public:
  62   NS_DECLARE_STATIC_IID_ACCESSOR(NS_WRAPPERCACHE_IID)
  63
  64   nsWrapperCache() : mWrapperPtrBits(0)
  65   {
  66   }
  67   ~nsWrapperCache()
  68   {
  69     NS_ASSERTION(!PreservingWrapper(),
  70                  "Destroying cache with a preserved wrapper!");
  71   }
  72
  73   JSObject* GetWrapper() const
  74   {
  75     return reinterpret_cast<JSObject*>(mWrapperPtrBits & ~kWrapperBitMask);
  76   }
  77
  78   void SetWrapper(JSObject* aWrapper)
  79   {
  80     NS_ASSERTION(!PreservingWrapper(), "Clearing a preserved wrapper!");
  81     mWrapperPtrBits = reinterpret_cast<PtrBits>(aWrapper) |
  82                       (mWrapperPtrBits & WRAPPER_IS_PROXY);
  83   }
  84
  85   void ClearWrapper()
  86   {
  87     NS_ASSERTION(!PreservingWrapper(), "Clearing a preserved wrapper!");
  88     mWrapperPtrBits = 0;
  89   }
  90
  91   void SetPreservingWrapper(PRBool aPreserve)
  92   {
  93     if(aPreserve) {
  94       mWrapperPtrBits |= WRAPPER_BIT_PRESERVED;
  95     }
  96     else {
  97       mWrapperPtrBits &= ~WRAPPER_BIT_PRESERVED;
  98     }
  99   }
 100
 101   PRBool PreservingWrapper()
 102   {
 103     return (mWrapperPtrBits & WRAPPER_BIT_PRESERVED) != 0;
 104   }
 105
 106   void SetIsProxy()
 107   {
 108       mWrapperPtrBits |= WRAPPER_IS_PROXY;
 109   }
 110
 111   PRBool IsProxy()
 112   {
 113       return (mWrapperPtrBits & WRAPPER_IS_PROXY) != 0;
 114   }
 115
 116 private:
 117   enum { WRAPPER_BIT_PRESERVED = 1 << 0 };
 118   enum { WRAPPER_IS_PROXY = 1 << 1 };
 119   enum { kWrapperBitMask = (WRAPPER_BIT_PRESERVED | WRAPPER_IS_PROXY) };
 120
 121   PtrBits mWrapperPtrBits;
 122 };
 123
 124 NS_DEFINE_STATIC_IID_ACCESSOR(nsWrapperCache, NS_WRAPPERCACHE_IID)
 125
 126 #define NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY                                   \
 127   if ( aIID.Equals(NS_GET_IID(nsWrapperCache)) ) {                            \
 128     *aInstancePtr = static_cast<nsWrapperCache*>(this);                       \
 129     return NS_OK;                                                             \
 130   }
 131
 132 #endif /* nsWrapperCache_h___ */