如何在 Swift 中设置实时线程？

Question

我正在尝试在 Swift 中实现set_realtime()此OSX 调度指南中的功能。

我被困住了thread_policy_set()。以下导致此编译器错误：

“不能专门化非通用定义”

我还尝试了其他一些事情，但遇到各种类型不匹配错误&policy。任何建议将不胜感激！谢谢！

func set_realtime(period: UInt32, computation: UInt32, constraint: UInt32) -> Bool {
    let TIME_CONSTRAINT_POLICY: UInt32 = 2
    let TIME_CONSTRAINT_POLICY_COUNT = UInt32(MemoryLayout<thread_time_constraint_policy_data_t>.size / MemoryLayout<integer_t>.size)
    let SUCCESS: Int32 = 0
    var policy: thread_time_constraint_policy
    var ret: Int32
    let thread: thread_port_t = pthread_mach_thread_np(pthread_self())

    policy.period = period
    policy.computation = computation
    policy.constraint = constraint
    policy.preemptible = 1

    ret = withUnsafeMutablePointer<integer_t>(to: &policy, { ptr -> Int32 in
        thread_policy_set(thread, TIME_CONSTRAINT_POLICY, ptr, TIME_CONSTRAINT_POLICY_COUNT)
    })

    if ret != SUCCESS {
        print(stderr, "set_realtime() failed.\n")
        return false
    }
    return true
}

Answer 1

您无法添加类型占位符来withUnsafeMutablePointer()将指针强制转换为其他类型。您必须“重新绑定”指针：

ret = withUnsafeMutablePointer(to: &policy) {
    $0.withMemoryRebound(to: integer_t.self, capacity: Int(TIME_CONSTRAINT_POLICY_COUNT)) {
        thread_policy_set(thread, TIME_CONSTRAINT_POLICY, $0, TIME_CONSTRAINT_POLICY_COUNT)
    }
}