Method apply

library/VTableInterpose.cpp:418–539

}

bool VMethodInterposeLinkBase::apply(bool enable)
{
    if (!enable)
    {
        remove();
        return true;
    }

    if (is_applied())
        return true;
    if (!host->vtable_ptr())
    {
        std::cerr << "VMethodInterposeLinkBase::apply(" << enable << "): " << name()
            << ": no vtable pointer: " << host->getName() << endl;
        return false;
    }

    // Retrieve the current vtable entry
    auto l = host->get_interpose(vmethod_idx);

    VMethodInterposeLinkBase* old_link = (l != nullptr) ? l : nullptr;
    VMethodInterposeLinkBase* next_link = nullptr;

    while (old_link && old_link->host == host && old_link->priority > priority)
    {
        next_link = old_link;
        old_link = old_link->prev;
    }

    void *old_ptr = next_link ? next_link->saved_chain : host->get_vmethod_ptr(vmethod_idx);
    assert(old_ptr != NULL && (!old_link || old_link->interpose_method == old_ptr));

    // Apply the new method ptr
    MemoryPatcher patcher;

    set_chain(old_ptr);

    if (next_link)
    {
        next_link->set_chain(interpose_method);
    }
    else if (!host->set_vmethod_ptr(patcher, vmethod_idx, interpose_method))
    {
        std::cerr << "VMethodInterposeLinkBase::apply(" << enable << "): " << name() << ": set_vmethod_ptr failed" << endl;
        set_chain(NULL);
        return false;
    }

    // Push the current link into the home host
    applied = true;
    prev = old_link;
    next = next_link;

    if (next_link)
        next_link->prev = this;
    else
        host->set_interpose(vmethod_idx,this);