C++线程间共享数据-免费源码丞旭猿

intg_i=0;std::mutexg_i_mutex;voidsafe_increment(){std::lock_guardlock(g_i_mutex);//safe_increment结束时自动解锁g_i++;}

//defer_lock_tvoidtransfer(bank_account&from,bank_account&to,intamount){// 锁定两个互斥而不死锁std::lock(from.m,to.m);//对from.m和to.m加锁// 保证二个已锁定互斥在作用域结尾解锁std::lock_guard<std::mutex>lock1(from.m,std::adopt_lock);std::lock_guard<std::mutex>lock2(to.m,std::adopt_lock);from.balance-=amount;to.balance+=amount;}//try_to_lock_tfor(inti=1;i<=5000;i++){std::unique_lock<std::mutex>munique(mlock,std::try_to_lock);if(munique.owns_lock()==true){//加锁成功s+=i;}else{// 执行一些没有共享内存的代码}//adopt_lock_tvoidtransfer(bank_account&from,bank_account&to,intamount){// 保证二个已锁定互斥在作用域结尾解锁std::unique_lock<std::mutex>lock1(from.m,std::defer_lock);std::unique_lock<std::mutex>lock2(to.m,std::defer_lock);std::lock(lock1,lock2);//对互斥量加锁from.balance-=amount;to.balance+=amount;}

std::unique_lock<std::mutex>get_lock(){externstd::mutexsome_mutex;std::unique_lock<std::mutex>lk(some_mutex);//构造unique_lockprepare_data();returnlk;//返回unique_lock的指针，离开作用域lk不会被销毁，而是move到域外}voidprocess_data(){std::unique_lock<std::mutex>lk(get_lock());// 获得锁所有权do_something();}

std::once_flagflag1,flag2;voidsimple_do_once(){std::call_once(flag1,[](){std::cout<<"Simple example: called once\n";});}voidmay_throw_function(booldo_throw){if(do_throw){// 这会出现多于一次, 因为出现异常的话，其他的调用会得到尝试std::cout<<"throw: call_once will retry\n";throwstd::exception();}// 如果未发生异常，则保证函数只会被调用一次std::cout<<"Didnt throw, call_once will not attempt again\n";}voiddo_once(booldo_throw){try{std::call_once(flag2,may_throw_function,do_throw);}catch(...){}}intmain(){std::threadst1(simple_do_once);// 1std::threadst2(simple_do_once);// 2std::threadst3(simple_do_once);// 3std::threadst4(simple_do_once);// 4st1.join();st2.join();st3.join();st4.join();std::threadt1(do_once,true);//5std::threadt2(do_once,true);//6std::threadt3(do_once,false);//7std::threadt4(do_once,true);//8t1.join();t2.join();t3.join();t4.join();}可能的结果：Simpleexample://1、2、3、4只会成功调用一次calledonce//5、6、8会触发异常，现在的结果可能是5、6触发两次异常，7调用成功，8不会再触发调用而是立刻返回throw:call_oncewillretrythrow:call_oncewillretryDidntthrow,call_oncewillnotattemptagain

std::lock(m1,m2);//此处加锁，构造的lock_guard无需上锁，离开作用域自动解锁std::lock_guardlock1(m1,std::adopt_lock);std::lock_guardlock2(m2,std::adopt_lock);或者std::unique_locklock1(m1,std::defer_lock);std::unique_locklock2(m2,std::defer_lock);std::lock(lock1,lock2)//构造的unique_lock未上锁，此处加锁，离开作用域自动解锁

std::scoped_locklock(m1,m2);//等价代码1std::lock(m1,m2);std::lock_guard<std::mutex>lk1(m1,std::adopt_lock);std::lock_guard<std::mutex>lk2(m2,std::adopt_lock);//等价代码2std::unique_lock<std::mutex>lk1(m1,std::defer_lock);std::unique_lock<std::mutex>lk2(m2,std::defer_lock);std::lock(lk1,lk2);

classSaferCounter{std::shared_mutexmutex;unsignedintget()const{std::shared_lock<std::shared_mutex>lock(mutex);//获取共享锁，内部执行mutex.lock_shared()returnvalue_;//lock 析构, 执行mutex.unlock_shared();}unsignedintincrement(){std::unique_lock<std::shared_mutex>lock(mutex)//获取独占锁，内部执行mutex.lock()value++;returnvalue;//lock 析构, 执行mutex.unlock();}}