C++ JSCompartment::removeWrapper方法代码示例

// 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.
bool
js::RemapWrapper(JSContext *cx, JSObject *wobjArg, JSObject *newTargetArg)
{
    RootedObject wobj(cx, wobjArg);
    RootedObject newTarget(cx, newTargetArg);
    JS_ASSERT(IsCrossCompartmentWrapper(wobj));
    JS_ASSERT(!IsCrossCompartmentWrapper(newTarget));
    JSObject *origTarget = Wrapper::wrappedObject(wobj);
    JS_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.
    JS_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);
    JS_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. Neuter 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.address(), 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.
    JS_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).
    JS_ASSERT(wobj->isWrapper());
    wcompartment->putWrapper(ObjectValue(*newTarget), ObjectValue(*wobj));
    return true;
}

js::NukeCrossCompartmentWrapper(JSContext* cx, JSObject* wrapper)
{
    JSCompartment* comp = wrapper->compartment();
    auto ptr = comp->lookupWrapper(ObjectValue(*Wrapper::wrappedObject(wrapper)));
    if (ptr)
        comp->removeWrapper(ptr);
    NukeRemovedCrossCompartmentWrapper(cx, wrapper);
}