[英]access to a thread variable from main loop - c++ - windows
I'm completely new to the concept of thread. 我对线程的概念是全新的。
I have to use a thread to update some cv::mat variable from camera from my main program. 我必须使用线程从我的主程序中的相机更新一些cv :: mat变量。
I only know that thread mean problem to share variable :/ 我只知道线程意味着共享变量的问题:/
So I think that I can't use a general variable in both my main and in the thread 所以我认为我不能在我的主线程和线程中都使用通用变量
I'm using 我正在使用
#include <thread>
Here is my thread fct: 这是我的线程fct:
void MyThreadFunction()
{
cv::Mat a;
cv::Mat b;
while (1)
{
capture_L.read(a);
capture_R.read(b);
}
}
I'm calling it before entering in my main loop(for rendering). 在进入主循环(用于渲染)之前,我先调用它。 So my goal is to access a and b in my main function.
因此,我的目标是访问主函数中的a和b。 How can I do that?
我怎样才能做到这一点?
Indeed, if you access your a
and b
variables from several threads, there will be a problem of mutual exclusion. 实际上,如果您从多个线程访问
a
和b
变量,将存在相互排斥的问题。 This can be solved by using a mutex
. 这可以通过使用
mutex
来解决。 You need to lock
the mutex before read and/or write the variables, and unlock
it after. 您需要在读取和/或写入变量之前先
lock
互斥锁,然后再对其进行unlock
。 This can be done by lock_guard
. 这可以通过
lock_guard
完成。
You can do something like that : 您可以这样做:
#include <mutex>
#include <thread>
void MyThreadFunction(mutex& m, cv::Mat& a, cv::Mat& b)
{
while (1)
{
[ ... ]
{
lock_gard<mutex> l(m);
capture_L.read(a);
capture_R.read(b);
}
}
}
int main()
{
mutex m;
cv::Mat a, b;
thread t(MyTjreadFunction, ref(m), ref(a), ref(b));
{
lock_gard<mutex> l(m);
[ ... access a & b ... ]
}
t.join();
return 0;
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.