#include <sys/time.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>

using namespace std;

// The iteration count below needs to be in a reasonable range for the
// specific hardware this program is run on.  If you make a change to
// the inner loop that makes it slower (as assigned in the lab), you
// may also want to adjust the iteration count downward.

static const int ITERATIONS = 1000000;

// This program runs furiously away in a loop, writing a character to
// a temporary file each time around the loop.  It will stop only when
// interrupted or killed.  Every ITERATIONS times through its loop it
// prints a report of how long (in microseconds) it took to do the
// last ITERATIONS iterations.  The time is elapsed (wall clock) time,
// so that it includes not only time this process spent, but also time
// when the processor is busy running other processes.  The times are
// not actually accurate to the microsecond.  -Max Hailperin
// <max@gustavus.edu> 2007-08-22
   

int main(int argc, char *argv[]){
  FILE *outFile;  // temporary output file

  if((outFile = tmpfile()) == NULL){
    cerr << "Couldn't open temporary file." << endl;
    exit(1);
  }
  int outFd = fileno(outFile);  // convert to system-level file desciptor

  while(1){ // Do the timing test repeatedly until killed.
    timeval start, stop;
    
    if(gettimeofday(&start, 0) < 0){ // Get starting time.
      perror("gettimeofday");
      exit(1);
    }
    for(long i = ITERATIONS; i > 0; i--){ // the actual test
      char c = 'X'; // arbitrary character to write
      if(pwrite(outFd, &c, 1, 0) < 0){ // Write the 'X' out from c to temp file.
        perror("pwrite");
      }
    }
    if(gettimeofday(&stop, 0) < 0){ // Get ending time.
      perror("gettimeofday");
      exit(1);
    }
    long diff = stop.tv_sec - start.tv_sec;
    diff *= 1000000; // microseconds per second
    diff += stop.tv_usec - start.tv_usec;
    cout << diff << endl; // Print elapsed time.
  }
}