/*
** The next function tells whether a key or value can be cleared from
** a weak table. Non-collectable objects are never removed from weak
** tables. Strings behave as `values', so are never removed too. for
** other objects: if really collected, cannot keep them; for userdata
** being finalized, keep them in keys, but not in values
*/
static int iscleared (const TValue *o, int iskey) {
if (!iscollectable(o)) return 0;
if (ttisstring(o)) {
stringmark(rawtsvalue(o)); /* strings are `values', so are never weak */
return 0;
}
return iswhite(gcvalue(o)) ||
(ttisuserdata(o) && (!iskey && isfinalized(uvalue(o))));
}
LUA_API void lua_getuservalue (lua_State *L, int idx) {
StkId o;
lua_lock(L);
o = index2addr(L, idx);
api_check(L, ttisuserdata(o), "userdata expected");
if (uvalue(o)->env) {
sethvalue(L, L->top, uvalue(o)->env);
} else
setnilvalue(L->top);
api_incr_top(L);
lua_unlock(L);
}
LUA_API void lua_setuservalue (lua_State *L, int idx) {
StkId o;
lua_lock(L);
api_checknelems(L, 1);
o = index2addr(L, idx);
api_check(L, ttisuserdata(o), "userdata expected");
if (ttisnil(L->top - 1))
uvalue(o)->env = NULL;
else {
api_check(L, ttistable(L->top - 1), "table expected");
uvalue(o)->env = hvalue(L->top - 1);
luaC_objbarrier(L, gcvalue(o), hvalue(L->top - 1));
}
L->top--;
lua_unlock(L);
}
LUA_API int lua_isuserdata (lua_State *L, int idx) {
const TValue *o = index2addr(L, idx);
return (ttisuserdata(o) || ttislightuserdata(o));
}
LUA_API int lua_isuserdata (lua_State *L, int idx) {
const TObject *o = luaA_indexAcceptable(L, idx);
return (o != NULL && (ttisuserdata(o) || ttislightuserdata(o)));
}