gecko-dev/xpcom/io/nsFastLoadPtr.h

109 lines
4.3 KiB
C++

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: NPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Netscape 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/NPL/
*
* 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 Mozilla FastLoad code.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 2001
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Brendan Eich <brendan@mozilla.org> (original author)
*
* 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 NPL, 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 NPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef nsFastLoadPtr_h___
#define nsFastLoadPtr_h___
/**
* Mozilla FastLoad file object pointer template type.
*
* Use nsFastLoadPtr<T> rather than nsCOMPtr<T> when declaring a strong XPCOM
* ref member of a data structure that's conditionally loaded at application
* startup. You must be willing to tolerate the null mRawPtr test on every
* dereference of this member pointer, or else copy it to a local to optimize
* away the cost.
*/
#ifndef nsCOMPtr_h___
#include "nsCOMPtr.h"
#endif
#ifndef nsIFastLoadService_h___
#include "nsIFastLoadService.h"
#endif
/**
* nsFastLoadPtr is a template class, so we don't want a class static service
* pointer member declared in nsFastLoadPtr, above. Plus, we need special
* declaration magic to export data across DLL/DSO boundaries. So we use an
* old-fashioned global variable that refers weakly to the one true FastLoad
* service. This pointer is maintained by that singleton's ctor and dtor.
*/
PR_EXPORT_DATA(nsIFastLoadService*) gFastLoadService_;
template <class T>
class nsFastLoadPtr : public nsCOMPtr<T> {
public:
nsDerivedSafe<T>* get() const {
if (!this->mRawPtr) {
gFastLoadService_->GetFastLoadReferent(
NS_REINTERPRET_CAST(nsISupports**,
&this->mRawPtr));
}
return NS_REINTERPRET_CAST(nsDerivedSafe<T>*, this->mRawPtr);
}
/**
* Deserialize an nsFastLoadPtr from aInputStream, skipping the referent
* object, but saving the object's offset for later deserialization.
*
* Lowercase name _a la_ get, because it's called the same way -- not via
* operator->().
*/
nsresult read(nsIObjectInputStream* aInputStream) {
return gFastLoadService_->ReadFastLoadPtr(aInputStream,
NS_REINTERPRET_CAST(nsISupports**,
&this->mRawPtr));
}
/**
* Serialize an nsFastLoadPtr reference and possibly the referent object,
* if that object has not yet been serialized.
*
* Lowercase name _a la_ get, because it's called the same way -- not via
* operator->().
*/
nsresult write(nsIObjectOutputStream* aOutputStream) {
return gFastLoadService_->WriteFastLoadPtr(aOutputStream,
NS_REINTERPRET_CAST(nsISupports*,
this->mRawPtr));
}
};
#endif // nsFastLoadPtr_h___