// FILE: /Users/aaa/myfile/github/c99/elapsedtime.c
#include <stdio.h>
#include <unistd.h>  // usleep()
#include <time.h>

// KEY: get time, get nano second, get nanosecond
int main() {
    long nano = 1E9;
    struct timespec start_time, end_time;

    // Get the start time
    clock_gettime(CLOCK_REALTIME, &start_time);

    usleep(1000);

    // Get the end time
    clock_gettime(CLOCK_REALTIME, &end_time);

    printf("start_time.tv_sec  %09ld\n", start_time.tv_sec);
    printf("start_time.tv_nsec %09ld\n", start_time.tv_nsec);
    printf("end_time.tv_sec  %09ld\n", end_time.tv_sec);
    printf("end_time.tv_nsec %09ld\n", end_time.tv_nsec);

    // Calculate the elapsed time
    long seconds = end_time.tv_sec - start_time.tv_sec;
    long nanoseconds = end_time.tv_nsec - start_time.tv_nsec;

    // Print the elapsed time
    printf("Elapsed time: %ld %09ld seconds\n", seconds, nanoseconds);
    printf("Elapsed time: %ld %09f seconds\n", seconds, (double)nanoseconds/nano);
    return 0;
}

uint64_t time_second(){
  struct timeval tv;
  gettimeofday(&tv, NULL);
  return (uint64_t)tv.tv_sec;
}

uint64_t time_micro() {
  struct timeval tv;
  uint64_t micro = 1E6;
  gettimeofday(&tv, NULL);
  return ((uint64_t)tv.tv_sec * micro) + ((uint64_t)tv.tv_usec);
}

uint64_t time_nano() {
  struct timeval tv;
  uint64_t nano = 1E9;
  gettimeofday(&tv, NULL);
  return ((uint64_t)tv.tv_sec * nano) + ((uint64_t)tv.tv_usec * 1000);
}

struct timespec {
  time_t tv_sec;   // seconds
  long   tv_nsec;  // nanoseconds
};

struct timeval {
  time_t      tv_sec;     // seconds
  suseconds_t tv_usec;    // microseconds
};