gecko-dev/xpcom/glue/nsIWeakReferenceUtils.h

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3.2 KiB
C++

/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef nsIWeakReferenceUtils_h__
#define nsIWeakReferenceUtils_h__
#include "nsCOMPtr.h"
#include "nsIWeakReference.h"
typedef nsCOMPtr<nsIWeakReference> nsWeakPtr;
/**
*
*/
// a type-safe shortcut for calling the |QueryReferent()| member function
// T must inherit from nsIWeakReference, but the cast may be ambiguous.
template <class T, class DestinationType>
inline
nsresult
CallQueryReferent( T* aSource, DestinationType** aDestination )
{
NS_PRECONDITION(aSource, "null parameter");
NS_PRECONDITION(aDestination, "null parameter");
return aSource->QueryReferent(NS_GET_TEMPLATE_IID(DestinationType),
reinterpret_cast<void**>(aDestination));
}
class NS_COM_GLUE nsQueryReferent : public nsCOMPtr_helper
{
public:
nsQueryReferent( nsIWeakReference* aWeakPtr, nsresult* error )
: mWeakPtr(aWeakPtr),
mErrorPtr(error)
{
// nothing else to do here
}
virtual nsresult NS_FASTCALL operator()( const nsIID& aIID, void** ) const;
private:
nsIWeakReference* mWeakPtr;
nsresult* mErrorPtr;
};
inline
const nsQueryReferent
do_QueryReferent( nsIWeakReference* aRawPtr, nsresult* error = 0 )
{
return nsQueryReferent(aRawPtr, error);
}
/**
* Deprecated, use |do_GetWeakReference| instead.
*/
extern NS_COM_GLUE
nsIWeakReference*
NS_GetWeakReference( nsISupports* , nsresult* aResult=0 );
/**
* |do_GetWeakReference| is a convenience function that bundles up all the work needed
* to get a weak reference to an arbitrary object, i.e., the |QueryInterface|, test, and
* call through to |GetWeakReference|, and put it into your |nsCOMPtr|.
* It is specifically designed to cooperate with |nsCOMPtr| (or |nsWeakPtr|) like so:
* |nsWeakPtr myWeakPtr = do_GetWeakReference(aPtr);|.
*/
inline
already_AddRefed<nsIWeakReference>
do_GetWeakReference( nsISupports* aRawPtr, nsresult* error = 0 )
{
return dont_AddRef(NS_GetWeakReference(aRawPtr, error));
}
inline
void
do_GetWeakReference( nsIWeakReference* aRawPtr, nsresult* error = 0 )
{
// This signature exists solely to _stop_ you from doing a bad thing.
// Saying |do_GetWeakReference()| on a weak reference itself,
// is very likely to be a programmer error.
}
template <class T>
inline
void
do_GetWeakReference( already_AddRefed<T>& )
{
// This signature exists solely to _stop_ you from doing the bad thing.
// Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
// someone else is an automatic leak. See <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
}
template <class T>
inline
void
do_GetWeakReference( already_AddRefed<T>&, nsresult* )
{
// This signature exists solely to _stop_ you from doing the bad thing.
// Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
// someone else is an automatic leak. See <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
}
#endif