'os_unfair_lock' is the fastest locking in Swift

UnfairLock.swift

final class UnfairLock {
    private var _lock: UnsafeMutablePointer<os_unfair_lock>
    
    init() {
        _lock = UnsafeMutablePointer<os_unfair_lock>.allocate(capacity: 1)
        _lock.initialize(to: os_unfair_lock())
    }
    
    deinit {
        _lock.deallocate()
    }
    
    func locked<ReturnValue>(
        _ f: () throws -> ReturnValue
    ) rethrows -> ReturnValue {
        os_unfair_lock_lock(_lock)
        defer { os_unfair_lock_unlock(_lock) }
        return try f()
    }
}