void push(stored_ptr &&new_data) {
counted_node_ptr new_next{ 1, allocate_node() };
counted_node_ptr old_tail = tail.load();
for (;;) {
increase_external_count(tail, old_tail);
T* old_data = nullptr;
if (old_tail.get()->data.compare_exchange_strong(old_data, new_data.get())) {
counted_node_ptr old_next = { 0, nullptr };
if (!old_tail.get()->next.compare_exchange_strong(old_next, new_next)) {
deallocate_node(new_next.get());
new_next = old_next;
}
set_new_tail(old_tail, new_next);
new_data.release();
break;
}
else {
counted_node_ptr old_next = { 0, nullptr };
if (old_tail.get()->next.compare_exchange_strong(old_next, new_next)) {
old_next = new_next;
new_next.set(allocate_node());
}
set_new_tail(old_tail, old_next);
}
}
}
stored_ptr pop() {
counted_node_ptr old_head = head.load(std::memory_order_relaxed);
for (;;) {
increase_external_count(head, old_head);
node * const ptr = old_head.get();
if (ptr == tail.load().get())
return nullptr;
counted_node_ptr next = ptr->next.load();
if (head.compare_exchange_strong(old_head, next)) {
T * const res = ptr->data.exchange(nullptr);
free_external_counter(old_head);
return stored_ptr(res);
}
if (!ptr->release_ref())
deallocate_node(ptr);
}
}
std::unique_ptr<T> pop()
{
counted_node_ptr old_head=head.load(std::memory_order_relaxed);
for(;;)
{
increase_external_count(head,old_head);
node* const ptr=old_head.ptr;
if(ptr==tail.load().ptr)
{
return std::unique_ptr<T>();
}
counted_node_ptr next=ptr->next.load();
if(head.compare_exchange_strong(old_head,next))
{
T* const res=ptr->data.exchange(nullptr);
free_external_counter(old_head);
return std::unique_ptr<T>(res);
}
ptr->release_ref();
}
}
