gecko-dev/xpcom/ds/nsObserverList.cpp

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 * The Original Code is mozilla.org code.
 *
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#include "nsObserverList.h"

#include "pratom.h"
#include "nsAutoLock.h"
#include "nsAutoPtr.h"
#include "nsCOMPtr.h"
#include "nsIObserver.h"
#include "nsISimpleEnumerator.h"
#include "nsIWeakReference.h"

nsObserverList::nsObserverList(nsresult &rv)
{
    MOZ_COUNT_CTOR(nsObserverList);
    mLock = PR_NewLock();
    if (!mLock)
        rv = NS_ERROR_OUT_OF_MEMORY;
}

nsObserverList::~nsObserverList(void)
{
    MOZ_COUNT_DTOR(nsObserverList);
    if (mLock)
        PR_DestroyLock(mLock);
}

nsresult
nsObserverList::AddObserver(nsIObserver* anObserver, PRBool ownsWeak)
{
    NS_ENSURE_ARG(anObserver);

    nsAutoLock lock(mLock);

    nsCOMPtr<nsISupports> observerRef;
    if (ownsWeak) {
        nsCOMPtr<nsISupportsWeakReference>
            weakRefFactory(do_QueryInterface(anObserver));
        NS_ASSERTION(weakRefFactory,
                     "Doesn't implement nsISupportsWeakReference");
        if (weakRefFactory)
            weakRefFactory->
                GetWeakReference((nsIWeakReference**)(nsISupports**)
                                 getter_AddRefs(observerRef));
    } else {
        observerRef = anObserver;
    }
    if (!observerRef)
        return NS_ERROR_FAILURE;

    if (!mObservers.AppendObject(observerRef))
        return NS_ERROR_OUT_OF_MEMORY;

    return NS_OK;
}

nsresult
nsObserverList::RemoveObserver(nsIObserver* anObserver)
{
    NS_ENSURE_ARG(anObserver);

    nsAutoLock lock(mLock);

    if (mObservers.RemoveObject(anObserver))
        return NS_OK;

    nsCOMPtr<nsISupportsWeakReference>
        weakRefFactory(do_QueryInterface(anObserver));
    if (!weakRefFactory)
        return NS_ERROR_FAILURE;

    nsCOMPtr<nsIWeakReference> observerRef;
    weakRefFactory->GetWeakReference(getter_AddRefs(observerRef));

    if (!observerRef)
        return NS_ERROR_FAILURE;

    if (!mObservers.RemoveObject(observerRef))
        return NS_ERROR_FAILURE;

    return NS_OK;
}

class nsObserverEnumerator : public nsISimpleEnumerator
{
public:
    NS_DECL_ISUPPORTS
    NS_DECL_NSISIMPLEENUMERATOR

    nsObserverEnumerator(nsCOMArray<nsISupports> &aObservers);

private:
    ~nsObserverEnumerator() { }

    PRUint32 mIndex; // Counts down, ends at 0
    nsCOMArray<nsISupports> mObservers;
};

nsresult
nsObserverList::GetObserverList(nsISimpleEnumerator** anEnumerator)
{
    nsAutoLock lock(mLock);

    nsRefPtr<nsObserverEnumerator> e(new nsObserverEnumerator(mObservers));
    if (!e)
        return NS_ERROR_OUT_OF_MEMORY;

    NS_ADDREF(*anEnumerator = e);
    return NS_OK;
}

nsObserverEnumerator::nsObserverEnumerator(nsCOMArray<nsISupports> &aObservers)
{
    for (PRInt32 i = 0; i < aObservers.Count(); ++i) {
        nsCOMPtr<nsIWeakReference> weak(do_QueryInterface(aObservers[i]));
        if (weak) {
            nsCOMPtr<nsISupports> strong(do_QueryReferent(weak));
            if (strong)
                mObservers.AppendObject(strong);
        }
        else {
            mObservers.AppendObject(aObservers[i]);
        }
    }

    mIndex = mObservers.Count();
}

NS_IMPL_ISUPPORTS1(nsObserverEnumerator, nsISimpleEnumerator)

NS_IMETHODIMP
nsObserverEnumerator::HasMoreElements(PRBool *aResult)
{
    *aResult = (mIndex > 0);
    return NS_OK;
}

NS_IMETHODIMP
nsObserverEnumerator::GetNext(nsISupports* *aResult)
{
    if (!mIndex) {
        NS_ERROR("Enumerating after HasMoreElements returned false.");
        return NS_ERROR_UNEXPECTED;
    }

    --mIndex;
    NS_ADDREF(*aResult = mObservers[mIndex]);
    return NS_OK;
}