/*      $OpenBSD: recallocarray.c,v 1.1 2017/03/06 18:44:21 otto Exp $  */
/*
* Copyright (c) 2008, 2017 Otto Moerbeek <[email protected]>
*
* 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>

#include "compat.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;
}