/*  $OpenBSD: recallocarray.c,v 1.2 2021/03/18 11:16:58 claudio Exp $ */

/*

 * Copyright (c) 2008, 2017 Otto Moerbeek <otto@drijf.net>

 *

 * Permission to use, copy, modify, and distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN

 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 */

#include <errno.h>

#include <stdlib.h>

#include <stdint.h>

#include <string.h>

#include <unistd.h>

/*

 * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX

 * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW

 */

#define MUL_NO_OVERFLOW ((size_t)1 << (sizeof(size_t) * 4))

void *

recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)

{

  size_t oldsize, newsize;

  void *newptr;

  if (ptr == NULL)

    return calloc(newnmemb, size);

  if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&

      newnmemb > 0 && SIZE_MAX / newnmemb < size) {

    errno = ENOMEM;

    return NULL;

  }

  newsize = newnmemb * size;

  if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&

      oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {

    errno = EINVAL;

    return NULL;

  }

  oldsize = oldnmemb * size;

  /*

   * Don't bother too much if we're shrinking just a bit,

   * we do not shrink for series of small steps, oh well.

   */

  if (newsize <= oldsize) {

    size_t d = oldsize - newsize;

    if (d < oldsize / 2 && d < (size_t)getpagesize()) {

      memset((char *)ptr + newsize, 0, d);

      return ptr;

    }

  }

  newptr = malloc(newsize);

  if (newptr == NULL)

    return NULL;

  if (newsize > oldsize) {

    memcpy(newptr, ptr, oldsize);

    memset((char *)newptr + oldsize, 0, newsize - oldsize);

  } else

    memcpy(newptr, ptr, newsize);

  explicit_bzero(ptr, oldsize);

  free(ptr);

  return newptr;

}