C++多線程編程(二)
多線程是程序員必須掌握的一門技術(shù)，本文主要是針對(duì)于C++新標(biāo)準(zhǔn)中多線程庫(kù)，需要具備一定C++基礎(chǔ)方可學(xué)習(xí)。
本章節(jié)是C++多線程編程第二課，C++不熟悉的可以轉(zhuǎn)接C++專輯教程，本章節(jié)主要講解C++多線程編程中容器創(chuàng)建線程以及數(shù)據(jù)共享問(wèn)題。
#include <vector>#include <iostream>#include <thread>void printTest(int num){std::cout << "子線程:" << num << "啟動(dòng)" << std::endl;std::cout << "子線程:" << num << "結(jié)束" << std::endl;}int main(){std::vector<std::thread* > test;for (int i = 0; i < 10; i++){test.push_back(new std::thread(printTest, i));}for (auto& pmove : test){pmove->join();}std::cout << "主線程" << std::endl;return 0;}
1.只讀數(shù)據(jù):穩(wěn)定安全，不需要特殊處理，直接讀即可
#include <vector>#include <iostream>#include <thread>std::vector<int> g_data={ 1,2,3 };void printTest(int num){std::cout << "子線程:" << num << "讀操作" << std::endl;for (auto pmove : g_data){std::cout << pmove << std::endl;}}int main(){std::vector<std::thread* > test;for (int i = 0; i < 10; i++){test.push_back(new std::thread(printTest, i));}for (auto& pmove : test){pmove->join();}std::cout << "主線程" << std::endl;return 0;}
2.有讀有寫：需要做特別處理(寫只做寫，讀只做讀操作，保持共享數(shù)據(jù)只有唯一操作)，不然會(huì)引發(fā)奔潰
#include <list>#include <iostream>#include <thread>class SeaKing{public:void makeFriend(){for (int i = 0; i < 100000; i++){std::cout << "增加一個(gè)" << std::endl;mm.push_back(i);}}void breakUp(){for (int i = 0; i < 100000; i++){if (!mm.empty()){std::cout << "減少一個(gè):"<<mm.front() << std::endl;mm.pop_front();}else{std::cout << "已空" << std::endl;}}}protected:std::list<int> mm;};int main(){SeaKing man;std::thread t1(&SeaKing::makeFriend, &man);std::thread t2(&SeaKing::breakUp, &man);t1.join();t2.join();return 0;}//以上程序會(huì)異常退
1.互斥量mutex: 互斥量可以理解為鎖，他是一個(gè)mutex類的對(duì)象
通過(guò)調(diào)用成員函數(shù)lock函數(shù)進(jìn)行加鎖
通過(guò)調(diào)用成員函數(shù)unlock函數(shù)進(jìn)行解鎖
#include <list>#include <iostream>#include <thread>#include <mutex> //1.包含頭文件class SeaKing{public:void makeFriend(){for (int i = 0; i < 100000; i++){m_mutex.lock();std::cout << "增加一個(gè)" << std::endl;mm.push_back(i);m_mutex.unlock();}}bool readInfo(){m_mutex.lock(); //2.加鎖if (!mm.empty()){std::cout << "減少一個(gè):" << mm.front() << std::endl;mm.pop_front();m_mutex.unlock();return true;}m_mutex.unlock();return false;}void breakUp(){for (int i = 0; i < 100000; i++){int result = readInfo();if (result == false){std::cout << "已空" << std::endl;}}}protected:std::list<int> mm;std::mutex m_mutex; //創(chuàng)建互斥量對(duì)象};int main(){SeaKing man;std::thread t1(&SeaKing::makeFriend, &man);std::thread t2(&SeaKing::breakUp, &man);t1.join();t2.join();return 0;}
注意:lock函數(shù)與unlock都是成對(duì)出現(xiàn)，如果lock了沒(méi)有調(diào)用unlock會(huì)引發(fā)異常，abort終止程序
2.通過(guò)lock_guard加鎖。
#include <list>#include <iostream>#include <thread>#include <mutex>class SeaKing{public:void makeFriend(){std::lock_guard<std::mutex> sbguard(m_mutex);for (int i = 0; i < 100000; i++){std::cout << "增加一個(gè)" << std::endl;mm.push_back(i);}}bool readInfo(){std::lock_guard<std::mutex> sbguard(m_mutex);if (!mm.empty()){std::cout << "減少一個(gè):" << mm.front() << std::endl;mm.pop_front();return true;}return false;}void breakUp(){for (int i = 0; i < 100000; i++){int result = readInfo();if (result == false){std::cout << "已空" << std::endl;}}}protected:std::list<int> mm;std::mutex m_mutex;};int main(){SeaKing man;std::thread t1(&SeaKing::makeFriend, &man);std::thread t2(&SeaKing::breakUp, &man);t1.join();t2.join();return 0;}
其實(shí)lock_guard 在構(gòu)造函數(shù)中進(jìn)行l(wèi)ock，在析構(gòu)函數(shù)中進(jìn)行unlock，本質(zhì)上還是lock與unlock操作。
好了，創(chuàng)建線程就介紹到這里，大家可以先練習(xí)一下，下章節(jié)講解共享數(shù)據(jù)訪問(wèn)。喜歡的不如點(diǎn)個(gè)“在看”吧
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