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- /*
- * Copyright 2016-present Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- #pragma once
- #include <folly/synchronization/Hazptr.h>
- #include <string>
- namespace folly {
- /** Wide CAS.
- */
- template <typename T, template <typename> class Atom = std::atomic>
- class HazptrWideCAS {
- struct Node : public hazptr_obj_base<Node, Atom> {
- T val_;
- explicit Node(T v = {}) : val_(v) {}
- };
- Atom<Node*> node_;
- public:
- HazptrWideCAS() : node_(new Node()) {}
- ~HazptrWideCAS() {
- delete node_.load(std::memory_order_relaxed);
- }
- bool cas(T& u, T& v) {
- Node* n = new Node(v);
- hazptr_holder<Atom> hptr;
- Node* p;
- while (true) {
- p = hptr.get_protected(node_);
- if (p->val_ != u) {
- delete n;
- return false;
- }
- if (node_.compare_exchange_weak(
- p, n, std::memory_order_relaxed, std::memory_order_release)) {
- break;
- }
- }
- hptr.reset();
- p->retire();
- return true;
- }
- };
- } // namespace folly
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