/* Measure the time to sum a file of native-byte-order floating-point
 * numbers, as a kind of upper bound on how fast brute force can be.
 */

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

void die(char *why) {
  perror(why);
  abort();
}

int main(int argc, char **argv) {
  int fd = open(argv[1], O_RDONLY);
  if (fd < 0) die(argv[1]);

  struct stat st;
  if (fstat(fd, &st) < 0) die("fstat");

  size_t size = st.st_size;
  char *mapped = mmap(0, size, PROT_READ, MAP_SHARED, fd, 0);
  if (MAP_FAILED == mapped) die("mmap");

  float total = 0;
  size_t max_idx = size / sizeof(total);
  for (int i = 0; i < max_idx; i++) {
    total += ((float*)mapped)[i];
  }

  printf("%ld items totaling %f\n", (long)max_idx, total);

  return 0;
}