how to implement timer in c++ - c++

Question

i'm working on gesture recognition application and i would like to implement timer but i don't know how.
here is what i want to do: user should be showing one gesture for 3 seconds before next function happens.
now it looks like this:
if(left_index==1)
{
putText("correct",Point(95,195),FONT_HERSHEY_COMPLEX_SMALL,0.8,Scalar(0,255,0),1,CV_AA);
correct = true;
}
break;
i would like it to be like this: if(left_index==1) <- if this is true for 3 seconds than the {} happens.
thank you for help.

Answer 1

there is a built-in function called sleep. It will kind of put your program at rest for int x milliseconds
I will make a function wait(int seconds):
void wait(long seconds)
{
seconds = seconds * 1000;
sleep(seconds);
}
wait(1); //waits for 1 second or 1000 milliseconds

Answer 2

You could try the following:
#include <time.h>
#include <unistd.h>
// Whatever your context is ...
if(left_index==1)
{
clock_t init, now;
init=clock();
now=clock();
while((left_index==1) && ((now-init) / CLOCKS_PER_SEC) < 3))
{
sleep(100); // give other threads a chance!
now=clock();
}
if((left_index==1) && (now-init) / CLOCKS_PER_SEC) >= 3))
{
// proceed with stuff
putText
( "correct"
, Point(95,195)
, FONT_HERSHEY_COMPLEX_SMALL,0.8,Scalar(0,255,0),1,CV_AA);
correct = true;
}
}
For c++11 I'd prefer a solution involving the classes from std::chrono instead working with time.h.

Answer 3

Also, you can try doing the following :
#include <time.h>
clock_t init, final;
init=clock();
//
// do stuff
//
final=clock()-init;
cout << (double)final / ((double)CLOCKS_PER_SEC);
Check these links out for further reference :
http://www.cplusplus.com/forum/beginner/317/
http://www.cplusplus.com/reference/ctime/

Answer 4

assuming your app is running an update loop.
bool gesture_testing = false;
std::chrono::time_point time_start;
while(app_running) {
if (! gesture_testing) {
if (left_index == 1) {
gesture_testing = true;
time_start = std::chrono::high_resolution_clock::now();
}
} else {
if (left_index != 1) {
gesture_testing = false;
} else {
auto time_end = std::chrono::high_resolution_clock::now();
auto duration = std::chrono::duration_cast<std::chrono::seconds>(time_end - time_start);
if (duration.count() == 3) {
// do gesture function
gesture_testing = false;
}
}
}
}
this is the basic logic, you can write a timer class and refactor the body into one function to make room for other part of your app.