魔のkyo的BLOG

class Screen {
public:
    template<typename... Arg>
    void print(int x, int y, const char* fmt, Arg&&... arg) {
        move_to(x, y);
        printf(fmt, forward<Arg>(arg)...);
    }

    void move_to(int x, int y) {
        printf("\033[%d;%dH", x+1, y+1); // 移动光标
    }

    void hide_cursor() {
        printf("\033[?25l"); // 隐藏光标
    }

    void show_cursor() {
        printf("\033[?25h"); // 显示光标
    }

    void clear() {
        printf("\033[2J\n"); // 清屏
    }
};

#include <iostream>
#include <atomic>
#include <mutex>
#include <condition_variable>
#include <chrono>
#include <thread>
#include <future>

using namespace std;

class BusyWaitableCondition {
public:
    void Wait() {
        while(!_flag);
    }

    void Notify() {
        _flag = true;
    }

    void Reset() {
        _flag = false;
    }

private:
    std::atomic<bool> _flag = false;
};

class WaitableCondition {
public:
    void Wait() {
        std::unique_lock<std::mutex> lock(_mutex);
        if(!_flag) {
            _cv.wait(lock, [this](){ return _flag; });
        }
    }

    void Notify() {
        do {
            std::lock_guard<std::mutex> lock(_mutex);
            _flag = true;
        } while(false);
        _cv.notify_all();
    }

    void Reset() {
        std::lock_guard<std::mutex> lock(_mutex);
        _flag = false;
    }

private:
    std::mutex _mutex;
    std::condition_variable _cv;
    bool _flag = false;
};

int main() {
    WaitableCondition c1;
    auto fut1 = std::async(std::launch::async, [&]{
        c1.Wait(); // 等待条件1满足才继续执行
        cout << "Hello 1" << endl;
    });
    auto fut2 = std::async(std::launch::async, [&]{
        c1.Wait(); // 等待条件1满足才继续执行
        cout << "Hello 2" << endl;
    });

    this_thread::sleep_for(chrono::seconds(1));
    cout << "1" << endl;
    cout << "2" << endl;
    cout << "3" << endl;
    cout << "4" << endl;
    cout << "5" << endl;
    c1.Notify(); // 通知条件1满足了

    return 0;
}

class WaitableEvent {
public:
    WaitableEvent(): _fut(_promise.get_future()) {

    }

    void Wait() const {
        _fut.wait();
    }

    void Notify() {
        _promise.set_value();
    }

private:
    std::promise<void> _promise;
    std::future<void> _fut;
};

// WatchDog.h
#pragma once

#include <cstdint>
#include <mutex>
#include <thread>
#include <atomic>
#include <condition_variable>

class WatchDog {
public:
    WatchDog(int timeout=10, bool echo=false); // seconds
    ~WatchDog() { stop(); }
    void stop();
    void kick();

private:
    void dog();
    void bark();

private:
    const int _timeout;
    const int _echo;
    std::atomic<int64_t> _last_kicked_ts;

    std::mutex _mutex;
    bool _stopped; // protected by _mutex
    std::condition_variable _cond; // protected by _mutex

    std::thread _dog;
};

// WatchDog.cpp
#include "WatchDog.h"
#include <iostream>

using namespace std;

namespace {

int64_t get_gmtime_us(){
    std::chrono::system_clock clock;
    return std::chrono::duration_cast<std::chrono::microseconds>(
        clock.now().time_since_epoch()).count();
}

} // namespace


WatchDog::WatchDog(int timeout, bool echo)
: _timeout(timeout)
, _echo(echo)
, _last_kicked_ts(get_gmtime_us())
, _stopped(false)
, _dog(&WatchDog::dog, this) {
}


void WatchDog::stop() {
    do {
        std::unique_lock<std::mutex> lock(_mutex);
        _stopped = true;
        _cond.notify_one(); // wake up the dog
    } while(false);
    
    try {
        _dog.join();
    }
    catch (...) {
        // it's ok, could already be dead
    }
}

void WatchDog::kick() {
    _last_kicked_ts = get_gmtime_us();
}

void WatchDog::dog() {
    std::unique_lock<std::mutex> lock(_mutex);
    while (true) {
        if (_stopped) return;

        int64_t ts = get_gmtime_us();
        if (ts - _last_kicked_ts > _timeout * 1000000) {
            bark();
        }

        if (_echo) {
            std::cout << "Successful dog check"
                << " [ts] " << ts
                << " [last_kicked_ts] " << _last_kicked_ts << std::endl;
        }

        // wake up when notified, or every N seconds
        int n = std::max(_timeout / 3, 1);
        _cond.wait_for(lock, std::chrono::seconds(n));
    }
}

void WatchDog::bark() {
    if (_echo) {
        std::cout << "\n!!!!! WATCH DOG FAILURE TRIGGERED !!!!!" << std::endl;
    }
    abort();
}