gecko/xpcom/glue/nsWeakReference.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
2012-05-21 04:12:37 -07:00
* 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/. */
// nsWeakReference.cpp
#include "mozilla/Attributes.h"
#include "nsWeakReference.h"
#include "nsCOMPtr.h"
class nsWeakReference MOZ_FINAL : public nsIWeakReference
{
public:
// nsISupports...
NS_DECL_ISUPPORTS
// nsIWeakReference...
NS_DECL_NSIWEAKREFERENCE
private:
friend class nsSupportsWeakReference;
nsWeakReference( nsSupportsWeakReference* referent )
: mReferent(referent)
// ...I can only be constructed by an |nsSupportsWeakReference|
{
// nothing else to do here
}
~nsWeakReference()
// ...I will only be destroyed by calling |delete| myself.
{
if ( mReferent )
mReferent->NoticeProxyDestruction();
}
void
NoticeReferentDestruction()
// ...called (only) by an |nsSupportsWeakReference| from _its_ dtor.
{
mReferent = 0;
}
nsSupportsWeakReference* mReferent;
};
nsresult
nsQueryReferent::operator()( const nsIID& aIID, void** answer ) const
{
nsresult status;
if ( mWeakPtr )
{
if ( NS_FAILED(status = mWeakPtr->QueryReferent(aIID, answer)) )
*answer = 0;
}
else
status = NS_ERROR_NULL_POINTER;
if ( mErrorPtr )
*mErrorPtr = status;
return status;
}
NS_COM_GLUE nsIWeakReference* // or else |already_AddRefed<nsIWeakReference>|
NS_GetWeakReference( nsISupports* aInstancePtr, nsresult* aErrorPtr )
{
nsresult status;
nsIWeakReference* result = nullptr;
if ( aInstancePtr )
{
nsCOMPtr<nsISupportsWeakReference> factoryPtr = do_QueryInterface(aInstancePtr, &status);
if ( factoryPtr )
{
status = factoryPtr->GetWeakReference(&result);
}
// else, |status| has already been set by |do_QueryInterface|
}
else
status = NS_ERROR_NULL_POINTER;
if ( aErrorPtr )
*aErrorPtr = status;
return result;
}
NS_COM_GLUE nsresult
nsSupportsWeakReference::GetWeakReference( nsIWeakReference** aInstancePtr )
{
if ( !aInstancePtr )
return NS_ERROR_NULL_POINTER;
if ( !mProxy )
mProxy = new nsWeakReference(this);
*aInstancePtr = mProxy;
nsresult status;
if ( !*aInstancePtr )
status = NS_ERROR_OUT_OF_MEMORY;
else
{
NS_ADDREF(*aInstancePtr);
status = NS_OK;
}
return status;
}
NS_IMPL_ISUPPORTS1(nsWeakReference, nsIWeakReference)
NS_IMETHODIMP
nsWeakReference::QueryReferent( const nsIID& aIID, void** aInstancePtr )
{
return mReferent ? mReferent->QueryInterface(aIID, aInstancePtr) : NS_ERROR_NULL_POINTER;
}
void
nsSupportsWeakReference::ClearWeakReferences()
{
if ( mProxy )
{
mProxy->NoticeReferentDestruction();
mProxy = 0;
}
}