source engine DynAppSysFactory

class DynAppSysFactory
{
    struct InterfaceLinkedList_t
    {
        void* (*Function)();

        const char*             pName;
        InterfaceLinkedList_t*  pNext;
    };

    InterfaceLinkedList_t*  m_pList;
public:
    DynAppSysFactory ( const std::string& module );

    void* Get ( const std::string& name );
};

DynAppSysFactory::DynAppSysFactory ( const std::string& module )
{
    void* create_interface = GetProcAddress ( GetModuleHandleA ( module.c_str () ), "CreateInterface" );

    size_t jmp_instruction = (size_t)create_interface + 4;

    size_t jmp_target = jmp_instruction + *(size_t*)( jmp_instruction + 1 ) + 5;

    m_pList = **(InterfaceLinkedList_t***)( jmp_target + 6 );
}

void* DynAppSysFactory::Get ( const std::string& name )
{
    InterfaceLinkedList_t* pList = m_pList;

    size_t nLength = name.length ();

    while ( pList )
    {
        if ( !std::strncmp ( pList->pName, name.c_str (), nLength ) )
        {
            int nVersion = atoi ( pList->pName + nLength );

            if ( nVersion > 0 )
                return pList->Function ();
        }

        pList = pList->pNext;
    }

    return nullptr;
}

DynAppSysFactory ClientFactory  ( "client.dll" );
DynAppSysFactory EngineFactory  ( "engine.dll" );
DynAppSysFactory VGuiFactory    ( "vguimatsurface.dll" );
DynAppSysFactory VGui2Factory   ( "vgui2.dll" );

m_pClient       = (Source::IBaseClientDLL*) ClientFactory.Get ( "VClient" );
m_pEngine       = (Source::IVEngineClient*) EngineFactory.Get ( "VEngineClient" );
m_pPanel        = (Source::IPanel*) VGui2Factory.Get ( "VGUI_Panel" );
m_pSurface      = (Source::ISurface*) VGuiFactory.Get ( "VGUI_Surface" );
m_pModelInfo    = (Source::IVModelInfo*) EngineFactory.Get ( "VModelInfoClient" );
m_pEntList      = (Source::IClientEntityList*) ClientFactory.Get ( "VClientEntityList" );
m_pEngineTrace  = (Source::IEngineTrace*) EngineFactory.Get ( "EngineTraceClient" );