Cocos2dx的Lua与C++交互

• Cocos2dx里Lua与C是怎样交互的？
• • 一、Lua2C
  • • 1.从初始化一个主线程（协程）开始：
    • 2.进入register_all_cocos2dx
    • 3.进入lua_register_cocos2dx_Ref

今天的面试有被问到Lua与C的调用，一时也没说出个123来，回来抓紧补一下，嘻嘻

bool LuaStack::init(void)
{
	_state = lua_open();
	...
	register_all_cocos2dx(_state);
	...
}

我们注意到了register_all_cocos2dx这个func,主要是注册所有Cocos2dx基本的类到Lua里

• tolua_open
  注册Cocos方法前的准备工作

TOLUA_API void tolua_open (lua_State* L)
{
    int top = lua_gettop(L);
    //将tolua_opened压入栈
    lua_pushstring(L,"tolua_opened");
    //获取LUA_REGISTRYINDEX，然后取栈顶元素k(tolua_open),t[k]入栈顶
    lua_rawget(L,LUA_REGISTRYINDEX);
    if (!lua_isboolean(L,-1))
    {
    	//压入字符串tolua_opened
        lua_pushstring(L,"tolua_opened");
        //压入bool值1
        lua_pushboolean(L,1);
        //获取注册表t,取栈顶bool与字符串tolua_opened，t[tolua_opened]=1
        lua_rawset(L,LUA_REGISTRYINDEX);
        
        // create value root table
        //压入字符串TOLUA_VALUE_ROOT
        lua_pushstring(L, TOLUA_VALUE_ROOT);
        //创建table
        lua_newtable(L);
        //t[TOLUA_VALUE_ROOT] = table
        lua_rawset(L, LUA_REGISTRYINDEX);

#ifndef LUA_VERSION_NUM 
        
        lua_pushstring(L, "tolua_peers");
        lua_newtable(L);
        
        lua_newtable(L);//table1
        lua_pushliteral(L, "__mode");
        lua_pushliteral(L, "k");
        //table1[__model] = k
        lua_rawset(L, -3);                
        //setmetatable(table,table1)
        lua_setmetatable(L, -2);   
        lua_rawset(L,LUA_REGISTRYINDEX);
#endif
	......
    }
    lua_settop(L,top);
}

• tolua_module

TOLUA_API void tolua_module (lua_State* L, const char* name, int hasvar)
{
    if (name)
    {
        
        lua_pushstring(L,name);
        lua_rawget(L,-2);
        //判断_G[name]~=nil
        if (!lua_istable(L,-1))  
        {
        	//弹出刚才的空value
            lua_pop(L,1);
            //创建空表stack:_G,table
            lua_newtable(L);
            //压栈name stack:_G,table,name
            lua_pushstring(L,name);
            //拷贝栈顶-2上面的table stack:_G,table,name，tablecopy
            lua_pushvalue(L,-2);
            //tablecopy[name] = table stack:_G,table
            lua_rawset(L,-4);       
        }
    }
    else
    {
        
        lua_pushvalue(L,LUA_GLOBALSINDEX);
    }
    //设置元表的过程
    if (hasvar)
    {
        if (!tolua_ismodulemetatable(L))  
        {
            
            lua_newtable(L);
            tolua_moduleevents(L);
            if (lua_getmetatable(L,-2))
                lua_setmetatable(L,-2);  
            lua_setmetatable(L,-2);
        }
    }
    lua_pop(L,1);               
}

• tolua_beginmodule
  判断这个table的isclass，不是的话返回table;是的话返回他的元表

TOLUA_API void tolua_beginmodule (lua_State* L, const char* name)
{
    if (name) { // ... module
//---- now module[name] is a table, get it's metatable to store keys
        // get module[name]
        lua_pushstring(L,name); // ... module name
        lua_rawget(L,-2);       // ... module module[name]
        // Is module[name] a class table?
        lua_pushliteral(L, ".isclass");
        lua_rawget(L, -2);                  // stack: ... module module[name] class_flag
        //判断是否是一个class table:isclass == true
        if (lua_isnil(L, -1)) {
        	//返回table
            lua_pop(L, 1);                  // stack: ... module module[name]
            return;                         // not a class table, use origin table
        }
        lua_pop(L, 1);                      // stack: ... module class_table
        // get metatable
        if (lua_getmetatable(L, -1)) {  // ... module class_table mt
        	//返回table的mt
            lua_remove(L, -2);          // ... module mt
        }
//---- by SunLightJuly, 2014.6.5
    } else {
        lua_pushvalue(L,LUA_GLOBALSINDEX);
    }
}

• tolua_usertype

TOLUA_API void tolua_usertype (lua_State* L, const char* type)
{
    char ctype[128] = "const ";
    strncat(ctype,type,120);

    
    //这里创建了两个元表
    //执行  与set classname 操作
    if (tolua_newmetatable(L,ctype) && tolua_newmetatable(L,type))
    	//下面分析
        mapsuper(L,type,ctype);             
}

• mapsuper
  设置连个的继承关系

static void mapsuper (lua_State* L, const char* name, const char* base)
{
    
    lua_pushstring(L,"tolua_super");
    //获取super
    lua_rawget(L,LUA_REGISTRYINDEX);    
    //注册表R里获取名为name的元表
    luaL_getmetatable(L,name);          
    //获取tolua_super[mt]
    lua_rawget(L,-2);                   
    //如果是空的
    if (lua_isnil(L,-1))
    {
        
        lua_pop(L,1);
        lua_newtable(L);                    
        luaL_getmetatable(L,name);          
        lua_pushvalue(L,-2);                
        lua_rawset(L,-4);                   
        //相当于super[mt] = table
    }

    
    lua_pushstring(L,base);
    lua_pushboolean(L,1);
    lua_rawset(L,-3);                    

    
    //基类的k-v 复制到 name元表
    luaL_getmetatable(L,base);          
    lua_rawget(L,-3);                   
    if (lua_istable(L,-1))
    {
        
        lua_pushnil(L);  
        while (lua_next(L,-2) != 0)
        {
            
            lua_pushvalue(L,-2);    
            lua_insert(L,-2);       
            lua_rawset(L,-5);       
        }
    }
    lua_pop(L,3);                       
}

• tolua_cclass
  主要建立父子类的关系

mapinheritance(L,name,base);

mapinheritance(L,cname,name);

mapsuper(L,cname,cbase);

mapsuper(L,name,base);

• tolua_function
  注册C方法到栈顶

针对文档、注释、已经一些大哥的帖子做出的自己对于这个过程的注释。
如果哪里有问题，欢迎指正，谢谢。