#include <iostream>             // std::cout
#include <mutex>
#include <thread>         // std::thread
#include <condition_variable>

using namespace std;

mutex mu;
int flag = 10;
condition_variable cv;
void f(int num)
{
    for (int i = 0; i < 50; i++)
    {
        unique_lock<mutex> lk(mu); 
        while (flag != num) // 这里不能用if，一定要用while
            cv.wait(lk); // 条件变量调用wait会自动调用锁
        for (int j = 0; j < num; ++j)
        {
            cout << j << " ";
        }
        cout << endl;
        flag = (num == 10) ? 100 : 10;
        cv.notify_one();
    }
}

int main()
{
    thread child(f, 10);
    f(100);
    child.join();
    return 0;
}

#include <iostream>             // std::cout
#include <mutex>
#include <thread>         // std::thread
#include <condition_variable>

using namespace std;

mutex mu;
int flag = 0;
condition_variable cv;
void f(int num)
{
    for (int i = 0; i < 10; i++)
    {
        unique_lock<mutex> lk(mu); 
        while (flag != num) // 这里不能用if 一定要用while
            cv.wait(lk); // 条件变量调用wait会自动调用锁
        char c = ‘A‘ + flag;
        cout << c;
        flag = (flag+1)%3;
        cv.notify_all(); //唤醒其他进程
    }
}

int main()
{
    thread child1(f, 0);
    thread child2(f, 1);
    f(2);
    child1.join();
    child2.join();
    return 0;
}

#include <iostream>             // std::cout
#include <mutex>
#include <thread>         // std::thread
#include <condition_variable>

using namespace std;

mutex mu;
int flag = 0; // 改变flag的值，就改变了1234的输出顺序
condition_variable cv;

void f(int num)
{
    for (int i = 0; i < 100; i++)
    {
        unique_lock<mutex> lk(mu); 
        while (flag != num)
            cv.wait(lk); // 条件变量调用wait会自动调用锁
        cout << num + 1 << " ";
        flag = (flag + 1) % 4;
        cv.notify_all(); //唤醒其他进程
    }
}

int main()
{
    thread child1(f, 0);
    thread child2(f, 1);
    thread child3(f, 2);
    f(3);

    child1.join();
    child2.join();
    child3.join();
    cout << endl;

    //system("pause");
    return 0;
}

// future example
#include <iostream>             // std::cout
#include <mutex>
#include <thread>         // std::thread
#include <condition_variable>
#include <atomic>
#include <future>

using namespace std;


class rwlock {
private:
    mutex _lock;
    condition_variable _wcon, _rcon;
    unsigned _writer, _reader;
    int _active;
public:
    void read_lock() {
        unique_lock<mutex> lock(_lock);
        ++_reader;
        while (_active < 0 || _writer > 0)
            _rcon.wait(lock);
        --_reader;
        ++_active;
    }
    void write_lock() {
        unique_lock<mutex> lock(_lock);
        ++_writer;
        while (_active != 0)
            _wcon.wait(lock);
        --_writer;
        _active = -1;
    }
    void unlock() {
        unique_lock<mutex> lock(_lock);
        if (_active > 0) {
            --_active;
            if (_active == 0) _wcon.notify_one();
        }
        else {
            _active = 0;
            if (_writer > 0) _wcon.notify_one();
            else if (_reader > 0) _rcon.notify_all();
        }

    }
    rwlock() :_writer(0), _reader(0), _active(0) {
    }
};

void t1(rwlock* rwl) {
    while (1) {
        cout << "I want to write." << endl;
        rwl->write_lock();
        cout << "writing..." << endl;
        this_thread::sleep_for(chrono::seconds(5));
        rwl->unlock();
        this_thread::sleep_for(chrono::seconds(5));
    }
}

void t2(rwlock* rwl) {
    while (1) {
        cout << "t2-I want to read." << endl;
        rwl->read_lock();
        cout << "t2-reading..." << endl;
        this_thread::sleep_for(chrono::seconds(1));
        rwl->unlock();
    }
}

void t3(rwlock* rwl) {
    while (1) {
        cout << "t3-I want to read." << endl;
        rwl->read_lock();
        cout << "t3-reading..." << endl;
        this_thread::sleep_for(chrono::seconds(1));
        rwl->unlock();
    }
}

int main()
{
    rwlock* rwl = new rwlock();
    thread th1(t1, rwl);
    thread th2(t2, rwl);
    thread th3(t3, rwl);
    th1.join();
    th2.join();
    th3.join();

    system("pause");
    return 0;
}