读写锁实现

 

#include <mutex>

class readwrite_lock
{
public:
    readwrite_lock() : read_cnt(0)
    {
    }

    void readLock()
    {
        read_mtx.lock();
        if (++read_cnt == 1)
            write_mtx.lock();
        read_mtx.unlock();
    }

    void readUnlock()
    {
        read_mtx.lock();
        if (--read_cnt == 0)
            write_mtx.unlock();
        read_mtx.unlock();
    }

    void writeLock()
    {
        write_mtx.lock();
    }

    void writeUnlock()
    {
        write_mtx.unlock();
    }

private:
    mutex read_mtx;
    mutex write_mtx;
    int read_cnt; // 已加读锁个数
};