C++11 多线程框架、线程锁、等待条件、双缓冲的使用

做过相关工程很久了，没有记录，发现有些忘记了，又复习了一遍，这里记录下：

我这里的代码做过删减，直接运行不了，重点在于说明thread创建框架、锁的使用、条件等待以及双缓冲的使用！

#include <stdio.h>
#include <iostream>
//thread
#include "thread"
#include "mutex"
#include <condition_variable>

struct Content 
{
   char img_data[1843200];
};

// Forward function definitions:
using namespace cv;
using namespace std;
bool sendimg = false;
void get_img();//线程1函数
void detect_trafficcone(int argc, char** argv); //线程2函数
void get_imginfo(pair<Mat,string>& info);
pair<Mat,string> g_imginfo;//缓存1 
pair<Mat,string> g_imginfoT;//缓存2
mutex mutex_imginfo;//mutex锁
condition_variable cond_imginfo;//条件变量
bool g_imginfo_flag = false;//信号量
string g_send_img = "name=detector5;timestamp=";
bool g_send_flag = false;
mutex mutex_send_img;
condition_variable cond_send_img;

int main(int argc, char** argv)
{
    thread getframe(get_img);//起线程1
    sleep(3);
    thread getobjinfo(detect_trafficcone,argc, argv);//起线程2
    getobjinfo.join();//.join是等待式结束，上面运行完毕才结束线程
    getframe.join();
    return 0;
}

void get_imginfo(pair<Mat,string>& info)
{
　　//双缓冲交换数据
    g_imginfoT = info;
    info = g_imginfo;
    g_imginfo = g_imginfoT;

}
void detect_trafficcone(int argc, char** argv)
{
    
    while(true)
    {
                        
        pair<Mat,string> imginfo;
        unique_lock<mutex> lock_imginfo(mutex_imginfo);
        while(!g_imginfo_flag)
        {
             cond_imginfo.wait(lock_imginfo);//等待cond_imginfo条件提醒，接收到提醒後先上锁，然后检查个g_imginfo_flag是否满足条件，满足就向下进行，不满足解锁。
        }        
        get_imginfo(imginfo);
        g_imginfo_flag = false;
        lock_imginfo.unlock();
        Mat recv_img = imginfo.first;
        string timestamp = imginfo.second;

               cout<<"detect trafficcone ..."<<endl;
        imshow("recv_img",recv_img);
        waitKey(0);
        send_img = send_img + "trafficcone_num="+to_string(box_num)+posboxs;
        unique_lock<mutex> lock_send_img(mutex_send_img);//unique_lock互斥锁，管理mutex的工具，此时对mutex_send_img加锁
        g_send_img = send_img;    
        g_send_flag = true;    
        lock_send_img.unlock();//解锁，省略不写的话，该函数运行结束自动解锁
        cond_send_img.notify_all();//条件提醒
        cout<<"send_img:"<<send_img<<endl;
        
    }
}

void get_img()
{
    
    while(true)
    {        
        unique_lock<mutex> lock_imginfo(mutex_imginfo);
        g_imginfo.first = recv_img;
        g_imginfo.second = timestamp;
        g_imginfo_flag = true;
        lock_imginfo.unlock();
        cond_imginfo.notify_all();

        
        unique_lock<mutex> lock_send_img(mutex_send_img);
         while(!g_send_flag)
        {
             cond_send_img.wait(lock_send_img);
        }
        zmq::message_t req_message(strlen(g_send_img.c_str()));
            memcpy((void*)req_message.data(),g_send_img.c_str(), strlen(g_send_img.c_str()));
        REQsocket.send(req_message);
        g_send_flag = false;
        lock_send_img.unlock();    
                    
    }
}