#include <dirent.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

int scandir(const char* path, struct dirent*** res, int (*sel)(const struct dirent*),
            int (*cmp)(const struct dirent**, const struct dirent**)) {
  DIR* d = opendir(path);
  struct dirent *de, **names = 0, **tmp;
  size_t cnt = 0, len = 0;
  int old_errno = errno;

  if (!d)
    return -1;

  while ((errno = 0), (de = readdir(d))) {
    if (sel && !sel(de))
      continue;
    if (cnt >= len) {
      len = 2 * len + 1;
      if (len > SIZE_MAX / sizeof *names)
        break;
      tmp = realloc(names, len * sizeof *names);
      if (!tmp)
        break;
      names = tmp;
    }
    names[cnt] = malloc(de->d_reclen);
    if (!names[cnt])
      break;
    memcpy(names[cnt++], de, de->d_reclen);
  }

  closedir(d);

  if (errno) {
    if (names)
      while (cnt-- > 0)
        free(names[cnt]);
    free(names);
    return -1;
  }
  errno = old_errno;

  if (cmp)
    qsort(names, cnt, sizeof *names, (int (*)(const void*, const void*))cmp);
  *res = names;
  return cnt;
}