timer.h

#ifndef TIMER_H
#define TIMER_H

#include <ctime>
#include <iostream>
#include <iomanip>

class timer
{
 friend std::ostream& operator<<(std::ostream& os, timer& t);

 private:
  bool running;
  clock_t start_clock;
  time_t start_time;
  double acc_time;

  double elapsed_time();

 public:
  // 'running' is initially false.  A timer needs to be explicitly started
  // using 'start' or 'restart'
  timer() : running(false), start_clock(0), start_time(0), acc_time(0) { }

  void start(const char* msg = 0);
  void restart(const char* msg = 0);
  void stop(const char* msg = 0);
  void check(const char* msg = 0);

}; // class timer

//===========================================================================
// Return the total time that the timer has been in the "running"
// state since it was first "started" or last "restarted".  For
// "short" time periods (less than an hour), the actual cpu time
// used is reported instead of the elapsed time.

inline double timer::elapsed_time()
{
  time_t acc_sec = time(0) - start_time;
  if (acc_sec < 3600)
    return (clock() - start_clock) / (1.0 * CLOCKS_PER_SEC);
  else
    return (1.0 * acc_sec);

} // timer::elapsed_time

//===========================================================================
// Start a timer.  If it is already running, let it continue running.
// Print an optional message.

inline void timer::start(const char* msg)
{
  // Print an optional message, something like "Starting timer t";
  if (msg) std::cout << msg << std::endl;

  // Return immediately if the timer is already running
  if (running) return;

  // Set timer status to running and set the start time
  running = true;
  start_clock = clock();
  start_time = time(0);

} // timer::start

//===========================================================================
// Turn the timer off and start it again from 0.  Print an optional message.

inline void timer::restart(const char* msg)
{
  // Print an optional message, something like "Restarting timer t";
  if (msg) std::cout << msg << std::endl;

  // Set timer status to running, reset accumulated time, and set start time
  running = true;
  acc_time = 0;
  start_clock = clock();
  start_time = time(0);

} // timer::restart

//===========================================================================
// Stop the timer and print an optional message.

inline void timer::stop(const char* msg)
{
  // Print an optional message, something like "Stopping timer t";
  if (msg) std::cout << msg << std::endl;

  // Compute accumulated running time and set timer status to not running
  if (running) acc_time += elapsed_time();
  running = false;

} // timer::stop

//===========================================================================
// Print out an optional message followed by the current timer timing.

inline void timer::check(const char* msg)
{
  // Print an optional message, something like "Checking timer t";
  if (msg) std::cout << msg << " : ";

  std::cout << "Elapsed time [" << std::setiosflags(std::ios::fixed)
            << std::setprecision(2)
            << acc_time + (running ? elapsed_time() : 0) << "] seconds\n";

} // timer::check

//===========================================================================
// Allow timers to be printed to ostreams using the syntax 'os << t'
// for an ostream 'os' and a timer 't'.  For example, "cout << t" will
// print out the total amount of time 't' has been "running".

inline std::ostream& operator<<(std::ostream& os, timer& t)
{
  os << std::setprecision(2) << std::setiosflags(std::ios::fixed)
    << t.acc_time + (t.running ? t.elapsed_time() : 0);
  return os;
}

//===========================================================================

#endif // TIMER_H