Function checktab

ThirdParty/lua/lua/ltablib.c:36–52

** Check that 'arg' has a table and set access functions in 'ta' to raw ** or non-raw according to the presence of corresponding metamethods. */

** or non-raw according to the presence of corresponding metamethods.
*/
static void checktab (lua_State *L, int arg, TabA *ta) {
  ta->geti = NULL; ta->seti = NULL;
  if (lua_getmetatable(L, arg)) {
    lua_pushliteral(L, "__index");  /* 'index' metamethod */
    if (lua_rawget(L, -2) != LUA_TNIL)
      ta->geti = lua_geti;
    lua_pushliteral(L, "__newindex");  /* 'newindex' metamethod */
    if (lua_rawget(L, -3) != LUA_TNIL)
      ta->seti = lua_seti;
    lua_pop(L, 3);  /* pop metatable plus both metamethods */
  }
  if (ta->geti == NULL || ta->seti == NULL) {
    luaL_checktype(L, arg, LUA_TTABLE);  /* must be table for raw methods */
    if (ta->geti == NULL) ta->geti = lua_rawgeti;
    if (ta->seti == NULL) ta->seti = lua_rawseti;
  }
}


#define aux_getn(L,n,ta)	(checktab(L, n, ta), luaL_len(L, n))