Swift4.2不支持stdatomic原子布尔值的简单实现是什么？

import Foundation

class AtomicBool {
    private var value: Bool
    private var mutex: pthread_mutex_t = pthread_mutex_t()

    init(initialValue: Bool) {
        value = initialValue
        pthread_mutex_init(&mutex, nil)
    }

    func get() -> Bool {
        pthread_mutex_lock(&mutex)
        defer { pthread_mutex_unlock(&mutex) }
        return value
    }

    func set(_ newValue: Bool) {
        pthread_mutex_lock(&mutex)
        defer { pthread_mutex_unlock(&mutex) }
        value = newValue
    }
}