#include <math.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>

// The strndup() function shall be equivalent to the strdup() function,
// duplicating the provided s in a new block of memory allocated as if
// by using malloc(), with the exception being that strndup() copies at
// most size plus one bytes into the newly allocated memory, terminating
// the new string with a NUL character. If the length of s is larger
// than size, only size bytes shall be duplicated. If size is larger
// than the length of s, all bytes in s shall be copied into the new
// memory buffer, including the terminating NUL character. The newly
// created string shall always be properly terminated.
char *strndup(const char *s, size_t size) {
  size_t l = strlen(s);
  size_t real_l = min(l, size);
  char *r = malloc(real_l + 1);
  if (!r) {
    return NULL;
  }
  strlcpy(r, s, real_l);
  return r;
}