lua_rawlen
ref = (int)lua_rawlen(L, t) + 1; /* get a new reference */
lua_pushinteger(L, lua_rawlen(L, 1));
LUA_API size_t (lua_rawlen) (lua_State *L, int idx);
#define lua_strlen(L,i) lua_rawlen(L, (i))
#define lua_objlen(L,i) lua_rawlen(L, (i))