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非安全string

说明

c++标准未规定stl容器以及字符串的线程安全性，故std::string在多线程下是不安全的。

代码示例

#include <iostream>
#include <stdio.h>
using namespace std;std::string *sp = nullptr;void Read()
{for(int i = 0; i < 100000; i++){std::string  s = "";s = *sp;}
}void Write()
{for(int i = 0; i < 100000; i++){*sp = std::to_string(i);}
}int main()
{while(1){sp = new std::string("string test");std::thread t1(Read);std::thread t2(Write);t1.join();t2.join();delete sp;sp = nullptr;}return 0;
}

安全string

安全string类封装

• 使用std::recursive_mutex递归锁保证string多线程下的读写安全；

关于std::recursive_mutex，可以查看：https://blog.csdn.net/www_dong/article/details/132197541

class TSString 
{typedef std::lock_guard<std::recursive_mutex> RecursiveGuard;mutable std::recursive_mutex rmutex;   // 注意增加mutable修饰std::string str_;public:TSString() {}TSString(const TSString& str){Set(str.Get());}TSString& operator= (const TSString& str){if(this == &str)return *this;Set(str.Get());return *this;}void Set(const char* str){RecursiveGuard mtx(rmutex);if(NULL == str){str_ = "";}else{str_ = str;}}void Set(const std::string& str){RecursiveGuard mtx(rmutex);str_ = str;}std::string Get() const{std::string str;{	RecursiveGuard mtx(rmutex);str = str_;}return str;}int Compare(const char* str) const {if(NULL == str)return 1;RecursiveGuard mtx(rmutex);return str_.compare(str);}int Compare(const std::string& str) const{return Compare(str.c_str());}int Compare(const TSString& s) const{return Compare(s.Get());}	
};

代码示例

TSString *sp = nullptr;void Read()
{for(int i = 0; i < 5000; i++){TSString s;s.Set("");s = *sp;}
}void Write()
{for(int i = 0; i < 5000; i++){sp->Set(std::to_string(i));}
}int main()
{while(1){TSString s;s.Set("string test");sp = new TSString(s);std::thread t1(Read);std::thread t2(Write);t1.join();t2.join();delete sp;sp = nullptr;}return 0;
}