C++ wrappermap::Ptr类代码示例

// Given a cross-compartment wrapper |wobj|, update it to point to
// |newTarget|. This recomputes the wrapper with JS_WrapValue, and thus can be
// useful even if wrapper already points to newTarget.
// This operation crashes on failure rather than leaving the heap in an
// inconsistent state.
void
js::RemapWrapper(JSContext* cx, JSObject* wobjArg, JSObject* newTargetArg)
{
    RootedObject wobj(cx, wobjArg);
    RootedObject newTarget(cx, newTargetArg);
    MOZ_ASSERT(wobj->is<CrossCompartmentWrapperObject>());
    MOZ_ASSERT(!newTarget->is<CrossCompartmentWrapperObject>());
    JSObject* origTarget = Wrapper::wrappedObject(wobj);
    MOZ_ASSERT(origTarget);
    Value origv = ObjectValue(*origTarget);
    JSCompartment* wcompartment = wobj->compartment();

    AutoDisableProxyCheck adpc(cx->runtime());

    // If we're mapping to a different target (as opposed to just recomputing
    // for the same target), we must not have an existing wrapper for the new
    // target, otherwise this will break.
    MOZ_ASSERT_IF(origTarget != newTarget,
                  !wcompartment->lookupWrapper(ObjectValue(*newTarget)));

    // The old value should still be in the cross-compartment wrapper map, and
    // the lookup should return wobj.
    WrapperMap::Ptr p = wcompartment->lookupWrapper(origv);
    MOZ_ASSERT(&p->value().unsafeGet()->toObject() == wobj);
    wcompartment->removeWrapper(p);

    // When we remove origv from the wrapper map, its wrapper, wobj, must
    // immediately cease to be a cross-compartment wrapper. Nuke it.
    NukeCrossCompartmentWrapper(cx, wobj);

    // First, we wrap it in the new compartment. We try to use the existing
    // wrapper, |wobj|, since it's been nuked anyway. The wrap() function has
    // the choice to reuse |wobj| or not.
    RootedObject tobj(cx, newTarget);
    AutoCompartment ac(cx, wobj);
    if (!wcompartment->wrap(cx, &tobj, wobj))
        MOZ_CRASH();

    // If wrap() reused |wobj|, it will have overwritten it and returned with
    // |tobj == wobj|. Otherwise, |tobj| will point to a new wrapper and |wobj|
    // will still be nuked. In the latter case, we replace |wobj| with the
    // contents of the new wrapper in |tobj|.
    if (tobj != wobj) {
        // Now, because we need to maintain object identity, we do a brain
        // transplant on the old object so that it contains the contents of the
        // new one.
        if (!JSObject::swap(cx, wobj, tobj))
            MOZ_CRASH();
    }

    // Before swapping, this wrapper came out of wrap(), which enforces the
    // invariant that the wrapper in the map points directly to the key.
    MOZ_ASSERT(Wrapper::wrappedObject(wobj) == newTarget);

    // Update the entry in the compartment's wrapper map to point to the old
    // wrapper, which has now been updated (via reuse or swap).
    MOZ_ASSERT(wobj->is<WrapperObject>());
    if (!wcompartment->putWrapper(cx, CrossCompartmentKey(newTarget), ObjectValue(*wobj)))
        MOZ_CRASH();
}

void
JSCompartment::checkWrapperMapAfterMovingGC()
{
    /*
     * Assert that the postbarriers have worked and that nothing is left in
     * wrapperMap that points into the nursery, and that the hash table entries
     * are discoverable.
     */
    for (WrapperMap::Enum e(crossCompartmentWrappers); !e.empty(); e.popFront()) {
        e.front().mutableKey().applyToWrapped(CheckGCThingAfterMovingGCFunctor());
        e.front().mutableKey().applyToDebugger(CheckGCThingAfterMovingGCFunctor());

        WrapperMap::Ptr ptr = crossCompartmentWrappers.lookup(e.front().key());
        MOZ_RELEASE_ASSERT(ptr.found() && &*ptr == &e.front());
    }
}

void
JSCompartment::checkWrapperMapAfterMovingGC()
{
    /*
     * Assert that the postbarriers have worked and that nothing is left in
     * wrapperMap that points into the nursery, and that the hash table entries
     * are discoverable.
     */
    for (WrapperMap::Enum e(crossCompartmentWrappers); !e.empty(); e.popFront()) {
        CrossCompartmentKey key = e.front().key();
        CheckGCThingAfterMovingGC(key.debugger);
        CheckGCThingAfterMovingGC(key.wrapped);
        CheckGCThingAfterMovingGC(static_cast<Cell *>(e.front().value().get().toGCThing()));

        WrapperMap::Ptr ptr = crossCompartmentWrappers.lookup(key);
        MOZ_ASSERT(ptr.found() && &*ptr == &e.front());
    }
}

void
JSCompartment::checkWrapperMapAfterMovingGC()
{
    /*
     * Assert that the postbarriers have worked and that nothing is left in
     * wrapperMap that points into the nursery, and that the hash table entries
     * are discoverable.
     */
    JS::shadow::Runtime *rt = JS::shadow::Runtime::asShadowRuntime(runtimeFromMainThread());
    for (WrapperMap::Enum e(crossCompartmentWrappers); !e.empty(); e.popFront()) {
        CrossCompartmentKey key = e.front().key();
        JS_ASSERT(!IsInsideNursery(rt, key.debugger));
        JS_ASSERT(!IsInsideNursery(rt, key.wrapped));
        JS_ASSERT(!IsInsideNursery(rt, e.front().value().get().toGCThing()));

        WrapperMap::Ptr ptr = crossCompartmentWrappers.lookup(key);
        JS_ASSERT(ptr.found() && &*ptr == &e.front());
    }
}