timer function - how to improve?

[grizzlei]

I don't feel so comfortable using the following code I wrote. How can I make it better?

#include <time.h>
  void timer(int interval){
    clock_t timeInit = clock();
    while(true){
    clock_t timeTest = clock();
        if(timeTest - timeInit == interval){
            std::cout<<"stuff happened"<<std::endl;
            break;
        }
    }
}

this is my timer function and I use it as the following

int main()
{
while(true){
    timer(1000);
    //do stuff
}

 return 0;
}

[salem c]

Well what are you trying to do in the meantime?

It burns 100% of the CPU at the moment.

Also, your exit condition should be
if(timeTest - timeInit >= interval)
There's no reason to assume that clock() returns a monotonic +1 value.
If the value were to increase by +2 at the wrong moment, you could miss the == test completely.

From the manual page.

Note that the time can wrap around. On a 32-bit system where CLOCKS_PER_SEC equals 1000000 this function will return the same value approximately every 72 minutes.

So you also need to take into account when timeTest < timeInit, and act accordingly.

[grizzlei]

Well what are you trying to do in the meantime?

It burns 100% of the CPU at the moment.

Also, your exit condition should be
if(timeTest - timeInit >= interval)
There's no reason to assume that clock() returns a monotonic +1 value.
If the value were to increase by +2 at the wrong moment, you could miss the == test completely.

From the manual page.

Note that the time can wrap around. On a 32-bit system where CLOCKS_PER_SEC equals 1000000 this function will return the same value approximately every 72 minutes.

So you also need to take into account when timeTest < timeInit, and act accordingly.

In the meantime my server sends messages to clients every second, what I try do is receive messages on a given time interval. The code works, I'm doing what I intended to do , but in a dirty, dirty way. Burns the entire CPU as you said.

I'll make changes according to your suggestions and edit.

[nuderobmonkey]

Your program loops as long as 'interval' endures through your while loop.
If you want to save CPU power, you could make your program sleep for some time:

#include <chrono>
#include <iostream>
#include <thread>

void timer( int ms)
{
    std::this_thread::sleep_for( std::chrono::milliseconds( ms));
    std::cout << "stuff happend" << std::endl;
}

int main()
{
    std::cout << "Starting timer:\n";
    timer( 3000);
}

http://www.cplusplus.com/reference/thread/this_thread/sleep_for/