Method copy

flow/WriteOnlySet.actor.cpp:108–132

template <class T, class IndexType, IndexType CAPACITY>
std::vector<Reference<T>> WriteOnlySet<T, IndexType, CAPACITY>::copy() {
	std::vector<Reference<T>> result;
	for (int i = 0; i < CAPACITY; ++i) {
		auto ptr = _set[i].load();
		if (ptr) {
			ASSERT((ptr & LOCK) == 0); // if we lock something we need to immediately unlock after we're done copying
			// We attempt lock so this won't get deleted. We will try this only once, if the other thread removed the
			// object from the set between the previews lines and now, we just won't make it part of the result.
			if (_set[i].compare_exchange_strong(ptr, ptr | LOCK)) {
				T* entry = reinterpret_cast<T*>(ptr);
				ptr |= LOCK;
				entry->addref();
				// we try to unlock now. If this element was removed while we incremented the refcount, the element will
				// end up in the freeList, so we will decrement later.
				_set[i].compare_exchange_strong(ptr, ptr ^ LOCK);
				result.push_back(Reference(entry));
			}
		}
	}
	// after we're done we need to clean up all objects that contented on a lock. This won't be perfect (as some thread
	// might not yet added the object to the free list), but whatever we don't get now we'll clean up in the next
	// iteration
	freeList.consume_all([](auto toClean) { toClean->delref(); });
	return result;
}

template <class T, class IndexType>
WriteOnlyVariable<T, IndexType>::WriteOnlyVariable() : WriteOnlySet<T, IndexType, 1>() {}