C++ KidsPointer类代码示例

Shape *
PropertyTree::lookupChild(ThreadSafeContext *cx, Shape *parent, const StackShape &child)
{
    /* Keep this in sync with the logic of getChild above. */
    Shape *shape = nullptr;

    JS_ASSERT(parent);

    KidsPointer *kidp = &parent->kids;
    if (kidp->isShape()) {
        Shape *kid = kidp->toShape();
        if (kid->matches(child))
            shape = kid;
    } else if (kidp->isHash()) {
        if (KidsHash::Ptr p = kidp->toHash()->readonlyThreadsafeLookup(child))
            shape = *p;
    } else {
        return nullptr;
    }

#if defined(JSGC_INCREMENTAL) && defined(DEBUG)
    if (shape) {
        JS::Zone *zone = shape->arenaHeader()->zone;
        JS_ASSERT(!zone->needsIncrementalBarrier());
        JS_ASSERT(!(zone->isGCSweeping() && !shape->isMarked() &&
                    !shape->arenaHeader()->allocatedDuringIncremental));
    }
#endif

    return shape;
}

void
PropertyTree::removeChild(Shape *child)
{
    JS_ASSERT(!child->inDictionary());

    Shape *parent = child->parent;
    JS_ASSERT(parent);
    JS_ASSERT(!JSID_IS_VOID(parent->id));

    KidsPointer *kidp = &parent->kids;
    if (kidp->isShape()) {
        Shape *kid = kidp->toShape();
        if (kid == child)
            parent->kids.setNull();
        return;
    }

    kidp->toHash()->remove(child);
}

JS_ALWAYS_INLINE void
js::PropertyTree::orphanChildren(Shape *shape)
{
    KidsPointer *kidp = &shape->kids;

    JS_ASSERT(!kidp->isNull());

    if (kidp->isShape()) {
        Shape *kid = kidp->toShape();

        if (!JSID_IS_VOID(kid->id)) {
            JS_ASSERT(kid->parent == shape);
            kid->parent = NULL;
        }
    } else {
        KidsHash *hash = kidp->toHash();

        for (KidsHash::Range range = hash->all(); !range.empty(); range.popFront()) {
            Shape *kid = range.front();
            if (!JSID_IS_VOID(kid->id)) {
                JS_ASSERT(kid->parent == shape);
                kid->parent = NULL;
            }
        }

        hash->~KidsHash();
        js_free(hash);
    }

    kidp->setNull();
}

bool
PropertyTree::insertChild(JSContext *cx, UnrootedShape parent, UnrootedShape child)
{
    JS_ASSERT(!parent->inDictionary());
    JS_ASSERT(!child->parent);
    JS_ASSERT(!child->inDictionary());
    JS_ASSERT(cx->compartment == compartment);
    JS_ASSERT(child->compartment() == parent->compartment());

    KidsPointer *kidp = &parent->kids;

    if (kidp->isNull()) {
        child->setParent(parent);
        kidp->setShape(child);
        return true;
    }

    if (kidp->isShape()) {
        UnrootedShape shape = kidp->toShape();
        JS_ASSERT(shape != child);
        JS_ASSERT(!shape->matches(child));

        KidsHash *hash = HashChildren(shape, child);
        if (!hash) {
            JS_ReportOutOfMemory(cx);
            return false;
        }
        kidp->setHash(hash);
        child->setParent(parent);
        return true;
    }

    if (!kidp->toHash()->putNew(child, child)) {
        JS_ReportOutOfMemory(cx);
        return false;
    }

    child->setParent(parent);
    return true;
}

Shape *
PropertyTree::getChild(ExclusiveContext *cx, Shape *parentArg, StackShape &unrootedChild)
{
    RootedShape parent(cx, parentArg);
    JS_ASSERT(parent);

    Shape *existingShape = nullptr;

    /*
     * The property tree has extremely low fan-out below its root in
     * popular embeddings with real-world workloads. Patterns such as
     * defining closures that capture a constructor's environment as
     * getters or setters on the new object that is passed in as
     * |this| can significantly increase fan-out below the property
     * tree root -- see bug 335700 for details.
     */
    KidsPointer *kidp = &parent->kids;
    if (kidp->isShape()) {
        Shape *kid = kidp->toShape();
        if (kid->matches(unrootedChild))
        existingShape = kid;
    } else if (kidp->isHash()) {
        if (KidsHash::Ptr p = kidp->toHash()->lookup(unrootedChild))
        existingShape = *p;
    } else {
        /* If kidp->isNull(), we always insert. */
    }

#ifdef JSGC_INCREMENTAL
    if (existingShape) {
        JS::Zone *zone = existingShape->zone();
        if (zone->needsIncrementalBarrier()) {
            /*
             * We need a read barrier for the shape tree, since these are weak
             * pointers.
             */
            Shape *tmp = existingShape;
            MarkShapeUnbarriered(zone->barrierTracer(), &tmp, "read barrier");
            JS_ASSERT(tmp == existingShape);
        } else if (zone->isGCSweeping() && !existingShape->isMarked() &&
                   !existingShape->arenaHeader()->allocatedDuringIncremental)
        {
            /*
             * The shape we've found is unreachable and due to be finalized, so
             * remove our weak reference to it and don't use it.
             */
            JS_ASSERT(parent->isMarked());
            parent->removeChild(existingShape);
            existingShape = nullptr;
        }
    }
#endif

    if (existingShape)
        return existingShape;

    RootedGeneric<StackShape*> child(cx, &unrootedChild);

    Shape *shape = newShape(cx);
    if (!shape)
        return nullptr;

    new (shape) Shape(*child, parent->numFixedSlots());

    if (!insertChild(cx, parent, shape))
        return nullptr;

    return shape;
}

UnrootedShape
PropertyTree::getChild(JSContext *cx, Shape *parent_, uint32_t nfixed, const StackShape &child)
{
    AssertCanGC();

    {
        UnrootedShape shape = NULL;

        JS_ASSERT(parent_);

        /*
         * The property tree has extremely low fan-out below its root in
         * popular embeddings with real-world workloads. Patterns such as
         * defining closures that capture a constructor's environment as
         * getters or setters on the new object that is passed in as
         * |this| can significantly increase fan-out below the property
         * tree root -- see bug 335700 for details.
         */
        KidsPointer *kidp = &parent_->kids;
        if (kidp->isShape()) {
            UnrootedShape kid = kidp->toShape();
            if (kid->matches(child))
                shape = kid;
        } else if (kidp->isHash()) {
            if (KidsHash::Ptr p = kidp->toHash()->lookup(child))
                shape = *p;
        } else {
            /* If kidp->isNull(), we always insert. */
        }

#ifdef JSGC_INCREMENTAL
        if (shape) {
            JS::Zone *zone = shape->zone();
            if (zone->needsBarrier()) {
                /*
                 * We need a read barrier for the shape tree, since these are weak
                 * pointers.
                 */
                Shape *tmp = shape;
                MarkShapeUnbarriered(zone->barrierTracer(), &tmp, "read barrier");
                JS_ASSERT(tmp == shape);
            } else if (zone->isGCSweeping() && !shape->isMarked() &&
                       !shape->arenaHeader()->allocatedDuringIncremental)
            {
                /*
                 * The shape we've found is unreachable and due to be finalized, so
                 * remove our weak reference to it and don't use it.
                 */
                JS_ASSERT(parent_->isMarked());
                parent_->removeChild(shape);
                shape = NULL;
            }
        }
#endif

        if (shape)
            return shape;
    }

    StackShape::AutoRooter childRoot(cx, &child);
    RootedShape parent(cx, parent_);

    UnrootedShape shape = newShape(cx);
    if (!shape)
        return UnrootedShape(NULL);

    new (shape) Shape(child, nfixed);

    if (!insertChild(cx, parent, shape))
        return UnrootedShape(NULL);

    return shape;
}