boost 实现读写锁

 #include <boost/thread/shared_mutex.hpp>
 #include <boost/thread/locks.hpp>

 using BoostMutexWR = boost::shared_mutex;
 using BoostLockW = boost::unique_lock<BoostMutexWR>;
 using BoostLockR = boost::shared_lock<BoostMutexWR>;

 void usingLockWR()
 {
     BoostMutexWR m_bstm;    // 创建一个互斥对象

     // 1. 加读锁，对象析构时自动释放锁资源
     {
         BoostLockR lockR(m_bstm);
     }

     // 2. 加写锁，对象析构时自动释放锁资源
     {
         BoostLockW lockW(m_bstm);
     }
 }