LUA Userdata

1 lua中, userdata存在栈上元素里的只是指针, 他们都会在生命周期结束后被垃圾回收

2 userdata也可以关联元表，不过只能通过luaL_newmetatable创建的元表

3 如果你的userdata关联了一些用户数据，需要userdata失效时也清理掉，那附加的元表可以设置__gc

int __lua__call(lua_State* L)

{

//
//栈底是userdata,上面是参数如果有的话, 普通的C函数调用栈只有参数
//

printf("hello lua userdata called! ");

return 0;

}

int __lua__gc(lua_State* L)

{

printf("hello lua gc called! ");

return 0;

}

void testmatetable()

{

lua_State *L;

L = luaL_newstate();

luaL_openlibs(L);

lua_register(L, "sleep", sleep_c);

luaL_newmetatable(L, "lua.userdata.metatable");

lua_pushliteral(L,"__call");

lua_pushcfunction(L, __lua__call);

lua_settable(L,-3);

//创建__gc

lua_pushliteral(L,"__gc");

lua_pushcfunction(L, __lua__gc);

lua_settable(L,-3);

lua_pop(L, 1);

//int lua_setmetatable (lua_State *L, int index); 给LUA值设置metatable

//metatable存放在栈顶，LUA值通过index指出

//创建userdata并关联metatable

//unsigned int* fidptr = (unsigned int *)lua_newuserdata(L, sizeof(unsigned int));

//*fidptr = 998;

//值关联数字的话可以用lua_pushlightuserdata

lua_pushlightuserdata(L, (void*)998);

luaL_getmetatable(L, "lua.userdata.metatable");

lua_setmetatable(L, -2);

//现在栈顶上就只有创建的userdata了，把它设置到全局变量里面这样LUA能正常访问

lua_setfield(L, LUA_GLOBALSINDEX, "hellouserdata");

//.test

luaL_loadstring(L, "hellouserdata (1,2,3); sleep(2000)");

lua_call(L,0,0);

lua_close(L);

}