C++11 多線程框架、線程鎖、等待條件、雙緩沖的使用

做過相關工程很久了，沒有記錄，發現有些忘記了，又復習了一遍，這里記錄下：

我這里的代碼做過刪減，直接運行不了，重點在於說明thread創建框架、鎖的使用、條件等待以及雙緩沖的使用！

#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();//線程1函數
void detect_trafficcone(int argc, char** argv); //線程2函數
void get_imginfo(pair<Mat,string>& info);
pair<Mat,string> g_imginfo;//緩存1 
pair<Mat,string> g_imginfoT;//緩存2
mutex mutex_imginfo;//mutex鎖
condition_variable cond_imginfo;//條件變量
bool g_imginfo_flag = false;//信號量
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);//起線程1
    sleep(3);
    thread getobjinfo(detect_trafficcone,argc, argv);//起線程2
    getobjinfo.join();//.join是等待式結束，上面運行完畢才結束線程
    getframe.join();
    return 0;
}

void get_imginfo(pair<Mat,string>& info)
{
　　//雙緩沖交換數據
    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條件提醒，接收到提醒後先上鎖，然后檢查個g_imginfo_flag是否滿足條件，滿足就向下進行，不滿足解鎖。
        }        
        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互斥鎖，管理mutex的工具，此時對mutex_send_img加鎖
        g_send_img = send_img;    
        g_send_flag = true;    
        lock_send_img.unlock();//解鎖，省略不寫的話，該函數運行結束自動解鎖
        cond_send_img.notify_all();//條件提醒
        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();    
                    
    }
}