gecko-dev/xpcom/base/nsIWeakReference.idl

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/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* 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 the Mozilla browser.
*
* The Initial Developer of the Original Code is Netscape
* Communications, Inc. Portions created by Netscape are
* Copyright (C) 1999, Mozilla. All Rights Reserved.
*
* Original Author:
* Scott Collins <scc@mozilla.org>
*
* Contributor(s):
* Pierre Phaneuf <pp@ludusdesign.com>
*/
#include "nsISupports.idl"
/**
* An instance of |nsIWeakReference| is a proxy object that cooperates with
* its referent to give clients a non-owning, non-dangling reference. Clients
* own the proxy, and should generally manage it with an |nsCOMPtr| (see the
* type |nsWeakPtr| for a |typedef| name that stands out) as they would any
* other XPCOM object. The |QueryReferent| member function provides a
* (hopefully short-lived) owning reference on demand, through which clients
* can get useful access to the referent, while it still exists.
*
* @status FROZEN
* @version 1.0
* @see nsISupportsWeakReference
* @see nsWeakReference
* @see nsWeakPtr
*/
[scriptable, uuid(9188bc85-f92e-11d2-81ef-0060083a0bcf)]
interface nsIWeakReference : nsISupports
{
/**
* |QueryReferent| queries the referent, if it exists, and like |QueryInterface|, produces
* an owning reference to the desired interface. It is designed to look and act exactly
* like (a proxied) |QueryInterface|. Don't hold on to the produced interface permanently;
* that would defeat the purpose of using a non-owning |nsIWeakReference| in the first place.
*/
void QueryReferent( in nsIIDRef uuid, [iid_is(uuid), retval] out nsQIResult result );
};
/**
* |nsISupportsWeakReference| is a factory interface which produces appropriate
* instances of |nsIWeakReference|. Weak references in this scheme can only be
* produced for objects that implement this interface.
*
* @see nsIWeakReference
* @see nsSupportsWeakReference
*/
[scriptable, uuid(9188bc86-f92e-11d2-81ef-0060083a0bcf)]
interface nsISupportsWeakReference : nsISupports
{
/**
* |GetWeakReference| produces an appropriate instance of |nsIWeakReference|.
* As with all good XPCOM `getters', you own the resulting interface and should
* manage it with an |nsCOMPtr|.
*
* @see nsIWeakReference
* @see nsWeakPtr
* @see nsCOMPtr
*/
nsIWeakReference GetWeakReference();
};
%{C++
#ifndef nsCOMPtr_h__
#include "nsCOMPtr.h"
#endif
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_IID(DestinationType),
NS_REINTERPRET_CAST(void**, aDestination));
}
class NS_EXPORT nsQueryReferent : public nsCOMPtr_helper
{
public:
nsQueryReferent( nsIWeakReference* aWeakPtr, nsresult* error )
: mWeakPtr(aWeakPtr),
mErrorPtr(error)
{
// nothing else to do here
}
virtual nsresult 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);
}
class NS_COM nsGetWeakReference : public nsCOMPtr_helper
{
public:
nsGetWeakReference( nsISupports* aRawPtr, nsresult* error )
: mRawPtr(aRawPtr),
mErrorPtr(error)
{
// nothing else to do here
}
virtual nsresult operator()( const nsIID&, void** ) const;
private:
nsISupports* mRawPtr;
nsresult* mErrorPtr;
};
/**
* |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
const nsGetWeakReference
do_GetWeakReference( nsISupports* aRawPtr, nsresult* error = 0 )
{
return nsGetWeakReference(aRawPtr, error);
}
inline
void
do_GetWeakReference( nsIWeakReference* aRawPtr, nsresult* error = 0 )
{
// This signature exists soley 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 soley 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 soley 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>.
}
/**
* Deprecated, use |do_GetWeakReference| instead.
*/
extern NS_COM
nsIWeakReference*
NS_GetWeakReference( nsISupports* , nsresult* aResult=0 );
%}