prod/native/libcommon/code/SpinLock.h

/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch B.V. licenses this file to you 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 <atomic>

namespace elasticapm::php {

class SpinLock {
public:
    void lock() {
        while (flag.test_and_set(std::memory_order_acquire)) {
#if defined(__cpp_lib_atomic_flag_test) // https://en.cppreference.com/w/cpp/atomic/atomic_flag
            while (flag.test(std::memory_order_relaxed))
                ; // test lock
#endif
        }
    }

    void unlock() {
        flag.clear(std::memory_order_release);
    }

private:
    std::atomic_flag flag = ATOMIC_FLAG_INIT;
};

} // namespace elasticapm::php