Реализация retain

gistfile1.m

- (id)retain
__attribute__((aligned(16)))
{
    if (OBJC_IS_TAGGED_PTR(self)) return self;

    SideTable *table = SideTable::tableForPointer(self);

    if (OSSpinLockTry(&table->slock)) {
        table->refcnts[DISGUISE(self)] += 2;
        OSSpinLockUnlock(&table->slock);
        return self;
    }
    return _objc_rootRetain_slow(self);
}


id
_objc_rootRetain_slow(id obj)
{
    SideTable *table = SideTable::tableForPointer(obj);
    OSSpinLockLock(&table->slock);
    table->refcnts[DISGUISE(obj)] += 2;
    OSSpinLockUnlock(&table->slock);

    return obj;
}