// -*- C++ -*-
#ifndef CILK_EXAMPLE_UTIL_GETTIME_H_INCLUDED
#define CILK_EXAMPLE_UTIL_GETTIME_H_INCLUDED

/* 
 * This simple utility function hides Linux/Windows differences so that
 * we can provide examples with source code common to the different
 * platforms.
 */

#ifdef _WIN32
#include <Windows.h>
#else
#include <stdlib.h>
#include <sys/time.h>
#endif

/* example_get_time
 * get the time in milliseconds.  This means different things in Windows vs.
 * Unix.  In Windows, it's a call to GetTickCount() which is the uptime of
 * the system.  In Unix, it is implemented with gettimeofday() and sets the
 * counter to zero the first time example_get_time is called.
 *
 * returns: the number of milliseconds since the start time.
 */

extern "C++"
inline
int example_get_time()
{
#ifdef _WIN32
    // Windows implementation.
    return (int) GetTickCount();
    #else
    static timeval* start = NULL;
    struct timezone tzp ={0, 0};
    if (NULL == start) {
      // define the current time as 0.
      start = (timeval *) malloc(sizeof(timeval));
      gettimeofday(start, &tzp);
      return 0;
    } else {
      // subtract the start time from the current time.
      timeval end;
      long ms = 0;
      gettimeofday(&end, &tzp);
      ms = (end.tv_sec - start->tv_sec) * 1000;
      ms += ((int) end.tv_usec - (int) start->tv_usec) / 1000;
      return (int) ms;
    }
    #endif
}

/* example_random
 * hash the value, n, that is passed using a 32-bit LCG:
 *       (a * n + b) % c
 * The values of a, b, and c, are the same as those used in glibc.  This
 * function exists to provide random numbers that are consistent across
 * compilers and between 32 and 64 bit platforms.  It will also generate
 * consistent results in parallel, provided that each node in the call-
 * graph provides a consistent n.
 *
 * returns: the hashed value of n in the low 32 bits.
 */

extern "C++"
inline
unsigned int example_random(unsigned int n)
{
  // 32-bit LCG used by glibc.
  // We use this to keep random numbers consistent between 32 and 64 bit
  // platforms and between compilers.
  return (((unsigned int) 1103515245 * n) + (unsigned int) 12345) %
        (unsigned int) 0xFFFFFFFF;
}
#endif // CILK_EXAMPLE_UTIL_GETTIME_H_INCLUDED