ReadWriteLock.swift

public class ReadWriteLock {
    // MARK: - Instance variables

    private var lock = pthread_rwlock_t()
    private var attr = pthread_rwlockattr_t()

    // MARK: - Public

    public init() {
        pthread_rwlockattr_init(&attr)
        pthread_rwlock_init(&lock, &attr)
    }

    deinit {
        pthread_rwlock_destroy(&lock)
        pthread_rwlockattr_destroy(&attr)
    }

    public func readLock() {
        pthread_rwlock_rdlock(&lock)
    }

    public func writeLock() {
        pthread_rwlock_wrlock(&lock)
    }

    public func unlock() {
        pthread_rwlock_unlock(&lock)
    }
}

// MARK: - Functional extension

public extension ReadWriteLock {
    func writeLock(closure: () -> Void) {
        writeLock()
        closure()
        unlock()
    }

    func writeLockFetch<T>(closure: () -> T) -> T {
        writeLock()
        defer {
            unlock()
        }
        return closure()
    }

    func readLock(closure: () -> Void) {
        readLock()
        closure()
        unlock()
    }

    func readLockFetch<T>(closure: () -> T) -> T {
        readLock()
        defer {
            unlock()
        }
        return closure()
    }
}