Qt 多线程同步之互斥锁

爱被打了一巴掌 2022-11-09 16:21 362阅读 0赞

# 生产者-消费者模型 #

### 1.QMutex ###

QMutex需要配对使用lock()和unlock()来实现代码段的保护

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d6ejk1MzIwMDQ2Mw_size_16_color_FFFFFF_t_70][]

#ifndef MYTHREAD_H
    #define MYTHREAD_H
    
    #include <QThread>
    #include <QQueue>
    #include <QMutex>
    #include <QDebug>
    
    static int data = 100;
    static QQueue<int> que;
    static QMutex mutex;
    
    class Producer : public QThread
    {
        Q_OBJECT
    public:
        explicit Producer(QThread *parent)
            :QThread(parent)
        {
    
        }
    
    protected:
        void run()
        {
            for(int i=0;i<data;i++) //生产者生产的快
            {
                mutex.lock();
                que.enqueue(i);
                qDebug()<<"Producer produce: "<<QString::number(i);        
                mutex.unlock();
                msleep(100);
            }
        }
    
    };
    
    class Customer : public QThread
    {
        Q_OBJECT
    public:
        explicit Customer(QThread *parent,int id)
            :QThread(parent)
            ,m_id(id)
        {
    
        }
    protected:
        void run()
        {
            while(true)
            {
                mutex.lock();
                if(!que.isEmpty())
                {          
                    int num = que.dequeue();
                    qDebug()<<"Customer"<<QString::number(m_id)<<" consume:"<<QString::number(num);              
                }
                mutex.unlock();
                msleep(300);//生产者消费的慢
            }
        }
    
    private:
        int m_id = 0;
    };
    
    
    
    
    
    #endif // MYTHREAD_H

**建立3个消费者和一个生产者**

#include <QCoreApplication>
    #include "MyThread.h"
    
    int main(int argc, char *argv[])
    {
        QCoreApplication a(argc, argv);
    
        Producer producer(nullptr);
        Customer customer1(nullptr,1);
        Customer customer2(nullptr,2);
        Customer customer3(nullptr,3);
    
        producer.start();
        customer1.start();
        customer2.start();
        customer3.start();
    
        return a.exec();
    }

### 2.使用QMutexLocker ###

QMutexLocker是另外一个简化了互斥量处理的类。QMutexLocker构造函数接受一个互斥量作为参数并将其锁定，QMutexLocker的析构函数则将此互斥量解锁，所以在QMutexLocker实例变量的生存期内的代码段得到保护，自动进行互斥量的锁定和解锁。

#ifndef MYTHREAD_H
    #define MYTHREAD_H
    
    #include <QThread>
    #include <QQueue>
    #include <QMutex>
    #include <QMutexLocker>
    #include <QDebug>
    
    static int data = 100;
    static QQueue<int> que;
    static QMutex mutex;
    
    class Producer : public QThread
    {
        Q_OBJECT
    public:
        explicit Producer(QThread *parent)
            :QThread(parent)
        {
    
        }
    
    protected:
        void run()
        {
            for(int i=0;i<data;i++) //生产者生产的快
            {
                {
                    QMutexLocker locker(&mutex);
                    que.enqueue(i);
                    qDebug()<<"Producer produce: "<<QString::number(i);
                }
                msleep(100);
            }
        }
    
    };
    
    class Customer : public QThread
    {
        Q_OBJECT
    public:
        explicit Customer(QThread *parent,int id)
            :QThread(parent)
            ,m_id(id)
        {
    
        }
    protected:
        void run()
        {
            while(true)
            {
                {
                    QMutexLocker locker(&mutex);
                    if(!que.isEmpty())
                    {
                        int num = que.dequeue();
                        qDebug()<<"Customer"<<QString::number(m_id)<<" consume:"<<QString::number(num);
                    }
                }
                msleep(300);//生产者消费的慢
            }
        }
    
    private:
        int m_id = 0;
    };
    
    
    #endif // MYTHREAD_H

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