compat/recallocarray.c

   1 /*      $OpenBSD: recallocarray.c,v 1.1 2017/03/06 18:44:21 otto Exp $  */
   2 /*
   3  * Copyright (c) 2008, 2017 Otto Moerbeek <otto@drijf.net>
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 #include <errno.h>
  19 #include <stdlib.h>
  20 #include <stdint.h>
  21 #include <string.h>
  22 #include <unistd.h>
  23
  24 #include "compat.h"
  25
  26 /*
  27  * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
  28  * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
  29  */
  30 #define MUL_NO_OVERFLOW ((size_t)1 << (sizeof(size_t) * 4))
  31
  32 void *
  33 recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
  34 {
  35         size_t oldsize, newsize;
  36         void *newptr;
  37
  38         if (ptr == NULL)
  39                 return calloc(newnmemb, size);
  40
  41         if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
  42             newnmemb > 0 && SIZE_MAX / newnmemb < size) {
  43                 errno = ENOMEM;
  44                 return NULL;
  45         }
  46         newsize = newnmemb * size;
  47
  48         if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
  49             oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
  50                 errno = EINVAL;
  51                 return NULL;
  52         }
  53         oldsize = oldnmemb * size;
  54
  55         /*
  56          * Don't bother too much if we're shrinking just a bit,
  57          * we do not shrink for series of small steps, oh well.
  58          */
  59         if (newsize <= oldsize) {
  60                 size_t d = oldsize - newsize;
  61
  62                 if (d < oldsize / 2 && d < (size_t)getpagesize()) {
  63                         memset((char *)ptr + newsize, 0, d);
  64                         return ptr;
  65                 }
  66         }
  67
  68         newptr = malloc(newsize);
  69         if (newptr == NULL)
  70                 return NULL;
  71
  72         if (newsize > oldsize) {
  73                 memcpy(newptr, ptr, oldsize);
  74                 memset((char *)newptr + oldsize, 0, newsize - oldsize);
  75         } else
  76                 memcpy(newptr, ptr, newsize);
  77
  78         explicit_bzero(ptr, oldsize);
  79         free(ptr);
  80
  81         return newptr;
  82 }