#include <stdio.h>
#include <sys/mman.h>
#include <time.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <locale.h>
#include <sys/stat.h>
#include <fcntl.h>


#define handle_error(msg) \
           do { perror(msg); exit(EXIT_FAILURE); } while (0)


unsigned long long monotonic_timer()
{
  struct timespec time;
  if (clock_gettime(CLOCK_MONOTONIC, &time)) {
    handle_error("clock_gettime");
  }
  return time.tv_sec * 1000000000ULL + time.tv_nsec;
}


void measure_shared_anon_mmap(size_t size)
{
  unsigned long long t0, t_mmap, t_write, t_close, t_munmap;

  t0 = monotonic_timer();

  char* data = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
  if (!data) {
    handle_error("mmap");
  }
  t_mmap = monotonic_timer();

  for (size_t i = 0; i < size; i += 4096) {
    // write something in all pages
    data[i] = 'x';
  }
  t_write = monotonic_timer();

  // no close because we did't open a file
  t_close = monotonic_timer();

  munmap(data, size);
  t_munmap = monotonic_timer();

  setlocale(LC_NUMERIC, "");
  printf("mmap time   %'15lld ns\n", t_mmap - t0);
  printf("write time  %'15lld ns\n", t_write - t_mmap);
  printf("munmap time %'15lld ns\n", t_munmap - t_close);
  printf("--\n");
}


void measure_private_anon_mmap(size_t size)
{
  unsigned long long t0, t_mmap, t_write, t_close, t_munmap;

  t0 = monotonic_timer();

  char* data = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
  if (!data) {
    handle_error("mmap");
  }
  t_mmap = monotonic_timer();

  for (size_t i = 0; i < size; i += 4096) {
    // write something in all pages
    data[i] = 'x';
  }
  t_write = monotonic_timer();

  // no close because we did't open a file
  t_close = monotonic_timer();

  munmap(data, size);
  t_munmap = monotonic_timer();

  setlocale(LC_NUMERIC, "");
  printf("mmap time   %'15lld ns\n", t_mmap - t0);
  printf("write time  %'15lld ns\n", t_write - t_mmap);
  printf("munmap time %'15lld ns\n", t_munmap - t_close);
  printf("--\n");
}


void measure_shm_mmap(size_t size)
{
  unsigned long long t0, t_mmap, t_write, t_close, t_munmap;

  char* name = "/my-shm-object";
  shm_unlink(name);  // ignore errors
  t0 = monotonic_timer();
  int shm = shm_open(name, O_RDWR|O_CREAT|O_EXCL, 0);
  if (shm < 0) {
    handle_error("shm_open");
  }
  if (ftruncate(shm, size)) {
    handle_error("ftruncate");
  }
  char* data = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_SHARED, shm, 0);
  if (!data) {
    handle_error("mmap");
  }
  t_mmap = monotonic_timer();

  for (size_t i = 0; i < size; i += 4096) {
    // write something in all pages
    data[i] = 'x';
  }
  t_write = monotonic_timer();

  close(shm);
  t_close = monotonic_timer();

  munmap(data, size);
  t_munmap = monotonic_timer();

  setlocale(LC_NUMERIC, "");
  printf("mmap time   %'15lld ns\n", t_mmap - t0);
  printf("write time  %'15lld ns\n", t_write - t_mmap);
  printf("close time  %'15lld ns\n", t_close - t_write);
  printf("munmap time %'15lld ns\n", t_munmap - t_close);
  printf("--\n");
}


void bench_round(size_t size) {
  printf("shared anon mmap %lu bytes\n", size);
  measure_shared_anon_mmap(size);
  printf("private anon mmap %lu bytes\n", size);
  measure_private_anon_mmap(size);
  printf("posix shm + mmap %lu bytes\n", size);
  measure_shm_mmap(size);
  printf("\n");
}


int main(int argc, char** argv)
{
  bench_round(1024 * 1024);
  bench_round(128 * 1024 * 1024);
  bench_round(1024 * 1024 * 1024);
}