/**
* Sends the request to the first allocator, if it cannot fulfill the request
* then the next Allocator is created and so on
*/
block allocate(size_t n) noexcept
{
if (n == 0) {
return{};
}
block result = allocate_no_grow(n);
if (result) {
return result;
}
// no node at all there
if (root_.load() == nullptr) {
auto firstNode = create_node();
Node *nullNode = nullptr;
// test if in the meantime someone else has created a node
if (!root_.compare_exchange_weak(nullNode, firstNode)) {
erase_node(firstNode);
}
result = allocate_no_grow(n);
if (result) {
return result;
}
}
// a new node must be appended
auto newNode = create_node();
Node *nullNode = nullptr;
auto p = root_.load();
do {
p = root_;
while (p->next.load() != nullptr) {
p = p->next;
}
} while (!p->next.compare_exchange_weak(nullNode, newNode));
result = allocate_no_grow(n);
return result;
}
