gecko/dom/public/nsWrapperCache.h

138 lines
4.4 KiB
C++

/* ***** 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 Gecko DOM code.
*
* 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):
* Peter Van der Beken <peterv@propagandism.org>
*
* 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 nsWrapperCache_h___
#define nsWrapperCache_h___
#include "nsCycleCollectionParticipant.h"
typedef unsigned long PtrBits;
#define NS_WRAPPERCACHE_IID \
{ 0x3a51ca81, 0xddab, 0x422c, \
{ 0x95, 0x3a, 0x13, 0x06, 0x28, 0x0e, 0xee, 0x14 } }
/**
* Class to store the XPCWrappedNative for an object. This can only be used
* with objects that only have one XPCWrappedNative at a time (usually ensured
* by setting an explicit parent in the PreCreate hook for the class). This
* object can be gotten by calling QueryInterface, note that this breaks XPCOM
* rules a bit (this object doesn't derive from nsISupports).
*/
class nsWrapperCache
{
public:
NS_DECLARE_STATIC_IID_ACCESSOR(NS_WRAPPERCACHE_IID)
nsWrapperCache() : mWrapperPtrBits(0)
{
}
~nsWrapperCache()
{
if (PreservingWrapper()) {
GetWrapper()->Release();
}
}
/**
* This method returns an nsIXPConnectWrappedNative, but we want to avoid
* including nsIXPConnect, because we don't want to make everyone require
* JS and XPConnect.
*/
nsISupports* GetWrapper()
{
return reinterpret_cast<nsISupports*>(mWrapperPtrBits & ~kWrapperBitMask);
}
/**
* This method takes an nsIXPConnectWrappedNative, but we want to avoid
* including nsIXPConnect, because we don't want to make everyone require
* JS and XPConnect.
*/
void SetWrapper(nsISupports* aWrapper)
{
NS_ASSERTION(!mWrapperPtrBits, "Already have a wrapper!");
mWrapperPtrBits = reinterpret_cast<PtrBits>(aWrapper);
}
void ClearWrapper()
{
if (PreservingWrapper()) {
GetWrapper()->Release();
}
mWrapperPtrBits = 0;
}
void PreserveWrapper()
{
NS_ASSERTION(mWrapperPtrBits, "No wrapper to preserve?");
if (!PreservingWrapper()) {
NS_ADDREF(reinterpret_cast<nsISupports*>(mWrapperPtrBits));
mWrapperPtrBits |= WRAPPER_BIT_PRESERVED;
}
}
void TraverseWrapper(nsCycleCollectionTraversalCallback &cb)
{
if (PreservingWrapper()) {
NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mWrapper");
cb.NoteXPCOMChild(GetWrapper());
}
}
private:
PRBool PreservingWrapper()
{
return mWrapperPtrBits & WRAPPER_BIT_PRESERVED;
}
enum { WRAPPER_BIT_PRESERVED = 1 << 0 };
enum { kWrapperBitMask = 0x1 };
PtrBits mWrapperPtrBits;
};
NS_DEFINE_STATIC_IID_ACCESSOR(nsWrapperCache, NS_WRAPPERCACHE_IID)
#define NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY \
if ( aIID.Equals(NS_GET_IID(nsWrapperCache)) ) { \
*aInstancePtr = static_cast<nsWrapperCache*>(this); \
return NS_OK; \
}
#endif /* nsWrapperCache_h___ */