C/C++编程：pthread_mutex_t封装&thread_mutex_guard的实现

清疚 2022-09-04 00:46 217阅读 0赞

*  [Unix/Linux编程：互斥锁与条件变量][Unix_Linux]

# 封装pthread\_mutex #

//
    // Created by oceanstar on 2021/8/9.
    //
    
    #ifndef OCEANSTAR_HTTP_THREAD_MUTEX_H
    #define OCEANSTAR_HTTP_THREAD_MUTEX_H
    
    #include <noncopyable.h>
    #include <bits/pthreadtypes.h>
    
    namespace oceanstar{
        
        /**
         * 线程互斥锁: 封装C语言的pthread_mutex，两者功能相同，但是由C变成Cpp类
         */
        class  thread_mutex : public noncopyable{
        
        public:
            /**
             * 构造方法
             * @param recursive {bool} 是否启用递归锁方式
             */
            thread_mutex(bool recursive = true);
            ~thread_mutex(void);
    
            /**
             * 对线程锁进行加锁，一直到加锁成功或内部失败(一般不会失败，除非是系统问题)
             * @return {bool} 返回 false 说明线程锁有问题
             */
            bool lock(void);
    
            /**
             * 尝试性加锁，无论成功与否都会立即返回
             * @return {bool} 返回 true 表示加锁成功，返回 false 表示加锁失败
             */
            bool try_lock(void);
    
            /**
             * 解线程锁
             * @return {bool} 返回 false 表示解锁失败，有可能之前并未加锁成功所致
             */
            bool unlock(void);
    
            /**
             * 获得 acl 中 C 版本的系统类型的线程锁
             * @return {acl_pthread_mutex_t*}
             */
            pthread_mutex_t* get_mutex(void) const;
    
        private:
            pthread_mutex_t* mutex_;
            pthread_mutexattr_t  mutex_attr_;
        };
    }
    
    #endif //OCEANSTAR_HTTP_THREAD_MUTEX_H

//
    // Created by oceanstar on 2021/8/9.
    //
    
    #include <cstdlib>
    #include <pthread.h>
    #include <cstring>
    #include <cerrno>
    #include <log.h>
    #include "thread_mutex.h"
    
    
    namespace oceanstar{
        
        thread_mutex::thread_mutex(bool recursive /* = true */){
        
            mutex_ = (pthread_mutex_t*)calloc(1, sizeof(pthread_mutex_t));
            int ret = pthread_mutexattr_init(&mutex_attr_);
            if (ret) {
        
                logger_fatal("pthread_mutexattr_init error=%s", strerror(errno));
            }
            if (recursive && (ret = pthread_mutexattr_settype(&mutex_attr_,PTHREAD_MUTEX_RECURSIVE))) {
        
                logger_fatal("pthread_mutexattr_settype error=%s", strerror(errno));
            }
            ret = pthread_mutex_init(mutex_, &mutex_attr_);
            if (ret) {
        
                logger_fatal("pthread_mutex_init error=%s", strerror(errno));
            }
        }
    
        thread_mutex::~thread_mutex(void){
        
            (void) pthread_mutexattr_destroy(&mutex_attr_);
        }
    
        pthread_mutex_t* thread_mutex::get_mutex(void) const
        {
        
            return mutex_;
        }
    
        bool thread_mutex::lock(void)
        {
        
            int ret = pthread_mutex_lock(mutex_);
            if (ret) {
        
                logger_error("pthread_mutex_lock error %s", strerror(errno));
                return false;
            }
            return true;
        }
    
        bool thread_mutex::try_lock(void)
        {
        
            return pthread_mutex_trylock(mutex_) == 0;
        }
    
        bool thread_mutex::unlock(void)
        {
        
            int ret = pthread_mutex_unlock(mutex_);
            if (ret) {
        
                logger_error("pthread_mutex_unlock error %s", strerror(errno));
                return false;
            }
            return true;
        }
    }

## 测试 ##

#include <iostream>
    #include <pthread.h>
    #include <thread_mutex.h>
    #include <thread>
    #include <mutex>
    
    
    int a = 0;
    void thread_tast(oceanstar::thread_mutex *lock){
        
        for(int i = 0; i < 100000; i++){
        
            lock->lock();
            a++;
            lock->unlock();
        }
        printf("a = %d\n", a);  // 锁能够保证最终结果一定相同（但不保证过程），如果不加锁的话每次运行结果都不一样
    }
    
    
    int main() {
        
       // std::mutex * lock= new std::mutex ;
        oceanstar::thread_mutex  *lock = new oceanstar::thread_mutex();
        std::thread t1(thread_tast, lock);
        std::thread t2(thread_tast, lock);
        t1.detach();
        t2.detach();
    
        getchar();
    
    
        return 0;
    }

![在这里插入图片描述][db82c1a7cff6467cab58ac8199e9ff3b.png]

**锁仅仅保证结果一定对，但是不保证过程**

# 实现thread\_mutex\_guard #

原理：析构函数的调用

namespace oceanstar{
        
        class  thread_mutex_guard : public noncopyable
        {
        
        public:
            thread_mutex_guard(thread_mutex& mutex);
    
            ~thread_mutex_guard(void);
    
        private:
            thread_mutex& mutex_;
        };
    }

namespace oceanstar{
        
        thread_mutex_guard::thread_mutex_guard(thread_mutex& mutex)
                : mutex_(mutex)
        {
        
            if (!mutex_.lock()) {
        
                logger_fatal("lock error=%s", strerror(errno));
            }
        }
    
        thread_mutex_guard::~thread_mutex_guard(void)
        {
        
            if (!mutex_.unlock()) {
        
                logger_fatal("unlock error=%s", strerror(errno));
            }
        }
    }

## 测试 ##

#include <iostream>
    #include <thread_mutex.h>
    #include <thread>
    #include <mutex>
    
    oceanstar::thread_mutex  lock ;
    int a = 0;
    void thread_tast(){
        
        for(int i = 0; i < 100000; i++){
        
            oceanstar::thread_mutex_guard mutexGuard(lock);
            a++;
        }
        printf("a = %d\n", a);  // 锁能够保证最终结果一定相同（但不保证过程），如果不加锁的话每次运行结果都不一样
    }
    
    
    int main() {
        
    
        std::thread t1(thread_tast);
        std::thread t2(thread_tast);
        t1.detach();
        t2.detach();
    
        getchar();
    
    
        return 0;
    }

[Unix_Linux]: https://blog.csdn.net/zhizhengguan/article/details/109819697
[db82c1a7cff6467cab58ac8199e9ff3b.png]: /images/20220829/c4b82c26b77544b7b55361a5e145aa08.png