Function GetUserdataFast

Plugins/UnLua/Source/UnLua/Private/LuaCore.cpp:370–407

* Get the address of userdata, fast path */

 * Get the address of userdata, fast path
 */
void* GetUserdataFast(lua_State *L, int32 Index, bool *OutTwoLvlPtr)
{
    bool bTwoLvlPtr = false;
    void* Userdata = nullptr;

    TValue* Value = GetTValue(L, Index);
    int32 Type = GetTValueType(Value);
    if (Type == LUA_TUSERDATA)
    {
        Udata* U = GetUdata(Value);
        uint8* Buffer = (uint8*)GetUdataMem(U);
        FUserdataDesc* UserdataDesc = GetUserdataDesc(U);
        if ((UserdataDesc)
            && (UserdataDesc->tag & BIT_VARIANT_TAG))// if the userdata has a variant tag
        {
            bTwoLvlPtr = (UserdataDesc->tag & BIT_TWOLEVEL_PTR) != 0;        // test if the userdata is a two level pointer
            if (UserdataDesc->tag & BIT_RELEASED_TAG)
                Userdata = nullptr;
            else
                Userdata = bTwoLvlPtr ? Buffer : Buffer + UserdataDesc->padding;    // add padding to userdata if it's not a two level pointer
        }
        else
        {
            Userdata = Buffer;
        }
    }
    else if (Type == LUA_TLIGHTUSERDATA)
    {
        Userdata = pvalue(Value);                                 // get the light userdata
    }

    if (OutTwoLvlPtr)
    {
        *OutTwoLvlPtr = bTwoLvlPtr;                                 // set two level pointer flag
    }

    return Userdata;
}

/**
 * Set metatable for the userdata/table on the top of the stack