/* Negative caching of a few fast metamethods. See the lj_meta_fast() macro. */
cTValue *lj_meta_cache(GCtab *mt, MMS mm, GCstr *name)
{
cTValue *mo = lj_tab_getstr(mt, name);
lua_assert(mm <= MM_FAST);
if (!mo || tvisnil(mo)) { /* No metamethod? */
mt->nomm |= (uint8_t)(1u<<mm); /* Set negative cache flag. */
return NULL;
}
return mo;
}
/* Lookup metamethod for object. */
cTValue *lj_meta_lookup(lua_State *L, cTValue *o, MMS mm)
{
GCtab *mt;
if (tvistab(o))
mt = tabref(tabV(o)->metatable);
else if (tvisudata(o))
mt = tabref(udataV(o)->metatable);
else
mt = tabref(basemt_obj(G(L), o));
if (mt) {
cTValue *mo = lj_tab_getstr(mt, mmname_str(G(L), mm));
if (mo)
return mo;
}
return niltv(L);
}
ptrdiff_t lj_vmevent_prepare(lua_State *L, VMEvent ev)
{
global_State *g = G(L);
GCstr *s = lj_str_newlit(L, LJ_VMEVENTS_REGKEY);
cTValue *tv = lj_tab_getstr(tabV(registry(L)), s);
if (tvistab(tv)) {
int hash = VMEVENT_HASH(ev);
tv = lj_tab_getint(tabV(tv), hash);
if (tv && tvisfunc(tv)) {
lj_state_checkstack(L, LUA_MINSTACK);
setfuncV(L, L->top++, funcV(tv));
return savestack(L, L->top);
}
}
g->vmevmask &= ~VMEVENT_MASK(ev); /* No handler: cache this fact. */
return 0;
}
