Friday, 1 April 2011

C++ Timer Class

Just thought I'd shove this somewhere public as it's probably useful for someone.

Earlier today I had a problem where boost::timer was always returning zero. The cause was boost::timer uses std::clock which only returns the elapsed CPU time. If you use sleep(), std::clock won't update!

So here's a little class that returns the elapsed time since the timer was instantiated (or restarted) which works with sleep().

 Copyright (C) 2011 by Luke Benstead  
   
 Permission is hereby granted, free of charge, to any person obtaining a copy  
 of this software and associated documentation files (the "Software"), to deal  
 in the Software without restriction, including without limitation the rights  
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell  
 copies of the Software, and to permit persons to whom the Software is  
 furnished to do so, subject to the following conditions:  
   
 The above copyright notice and this permission notice shall be included in  
 all copies or substantial portions of the Software.  
   
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR  
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE  
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER  
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,  
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN  
 THE SOFTWARE.  
   
 #ifndef TIMER_H_INCLUDED  
 #define TIMER_H_INCLUDED  
   
 #include <sys/time.h>  
   
 class Timer {  
 public:  
   Timer():  
     start_time_(now()) {  
   }  
   
   void restart() {  
     start_time_ = now();  
   }  
   
   double elapsed() const {  
     double t = now();  
   
     return double(t - start_time_);  
   }  
   
 private:  
   double now() const {  
     timeval t;  
     gettimeofday(&t, NULL);  
     return t.tv_sec + (t.tv_usec / 1000000.0);  
   }  
   
   double start_time_;  
 };  
   
 #endif // TIMER_H_INCLUDED  
   

Yeah I know, it's basic and anyone could've written it, but still might save someone 5 minutes :)

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