C++11 std::this_thread

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一 简介

std::this_thread是一个命名空间，包含一系列访问当前线程的函数。

二 4个函数

1 get_id

noexcept 获取线程id。

2 yield

noexcept 当前线程放弃执行，给实现重新调度的机会，允许其他线程运行，该线程回到准备状态，重新分配资源。
调用该方法后，可能执行其他线程，也可能还是执行该线程。

3 sleep_for

阻塞线程到指定时间段之后。

template <class Rep, class Period>
void sleep_for (const chrono::duration<Rep,Period>& rel_time);

4 sleep_until

阻塞线程到指定时间点。

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template <class Clock, class Duration>
void sleep_until (const chrono::time_point<Clock,Duration>& abs_time);

三 举例

void showThreadId(int num) {
  std::cout << "thread" << num << " id: " << std::this_thread::get_id() << std::endl;
}
 
void little_sleep(std::chrono::microseconds us) {
  auto start = std::chrono::high_resolution_clock::now();
  auto end = start + us;
  do {
    std::this_thread::yield();
  } while (std::chrono::high_resolution_clock::now() < end);
}
 
int main() {
  {
    // this_thread::get_id
    std::cout << "main thread id: " << std::this_thread::get_id() << std::endl;
    std::thread t1(showThreadId, 1);
    t1.join();
    std::thread t2(showThreadId, 2);
    t2.join();
  }
  std::cout << std::endl;
  std::cout << std::endl;
  {
    // this_thread::yield
    auto start = std::chrono::high_resolution_clock::now();
 
    little_sleep(std::chrono::microseconds(100));
 
    auto elapsed = std::chrono::high_resolution_clock::now() - start;
    std::cout << "waited for "
              << std::chrono::duration_cast<std::chrono::microseconds>(elapsed).count()
              << " microseconds" << std::endl;
  }
  std::cout << std::endl;
  std::cout << std::endl;
  {
    // this_thread::sleep_for
    std::cout << "countdown:\n";
    for (int i = 10; i > 0; --i) {
      std::cout << i << std::endl;
      std::this_thread::sleep_for(std::chrono::seconds(1));
    }
    std::cout << "Lift off!\n";
  }
  std::cout << std::endl;
  std::cout << std::endl;
  {
    // this_thread::sleep_until
    using std::chrono::system_clock;
    std::time_t tt = system_clock::to_time_t(system_clock::now());
 
    struct std::tm* ptm = std::localtime(&tt);
    std::cout << "Current time: " << std::put_time(ptm, "%X") << '\n';
 
    std::cout << "Waiting for the next minute to begin...\n";
    ++ptm->tm_min;
    ptm->tm_sec = 0;
    std::this_thread::sleep_until(system_clock::from_time_t(mktime(ptm)));
 
    std::cout << std::put_time(ptm, "%X") << " reached!\n";
  }
 
  system("pause");
  return 0;
}