compat_recallocarray.c

   1 #include "config.h"
   2
   3 #if HAVE_RECALLOCARRAY
   4
   5 int dummy;
   6
   7 #else
   8
   9 /*      $Id: compat_recallocarray.c,v 1.1 2017/06/12 19:05:47 schwarze Exp $ */
  10 /*      $OpenBSD: malloc.c,v 1.225 2017/05/13 07:11:29 otto Exp $ */
  11 /*
  12  * Copyright (c) 2017 Otto Moerbeek <otto@drijf.net>
  13  *
  14  * Permission to use, copy, modify, and distribute this software for any
  15  * purpose with or without fee is hereby granted, provided that the above
  16  * copyright notice and this permission notice appear in all copies.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  19  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  20  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  21  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  22  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  23  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  24  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  25  */
  26
  27 #include <sys/types.h>
  28 #include <errno.h>
  29 #include <stdint.h>
  30 #include <stdlib.h>
  31 #include <string.h>
  32
  33 /*
  34  * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
  35  * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
  36  */
  37 #define MUL_NO_OVERFLOW ((size_t)1 << (sizeof(size_t) * 4))
  38
  39 /*
  40  * Even though specified in POSIX, the PAGESIZE and PAGE_SIZE
  41  * macros have very poor portability.  Since we only use this
  42  * to avoid free() overhead for small shrinking, simply pick
  43  * an arbitrary number.
  44  */
  45 #define MALLOC_PAGESIZE         (1UL << 12)
  46
  47
  48 void *
  49 recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
  50 {
  51         size_t oldsize, newsize;
  52         void *newptr;
  53
  54         if (ptr == NULL)
  55                 return calloc(newnmemb, size);
  56
  57         if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
  58             newnmemb > 0 && SIZE_MAX / newnmemb < size) {
  59                 errno = ENOMEM;
  60                 return NULL;
  61         }
  62         newsize = newnmemb * size;
  63
  64         if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
  65             oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
  66                 errno = EINVAL;
  67                 return NULL;
  68         }
  69         oldsize = oldnmemb * size;
  70
  71         /*
  72          * Don't bother too much if we're shrinking just a bit,
  73          * we do not shrink for series of small steps, oh well.
  74          */
  75         if (newsize <= oldsize) {
  76                 size_t d = oldsize - newsize;
  77
  78                 if (d < oldsize / 2 && d < MALLOC_PAGESIZE) {
  79                         memset((char *)ptr + newsize, 0, d);
  80                         return ptr;
  81                 }
  82         }
  83
  84         newptr = malloc(newsize);
  85         if (newptr == NULL)
  86                 return NULL;
  87
  88         if (newsize > oldsize) {
  89                 memcpy(newptr, ptr, oldsize);
  90                 memset((char *)newptr + oldsize, 0, newsize - oldsize);
  91         } else
  92                 memcpy(newptr, ptr, newsize);
  93
  94         /*
  95          * At this point, the OpenBSD implementation calls
  96          * explicit_bzero() on the old memory before it is
  97          * freed.  Since explicit_bzero() is hard to implement
  98          * portably and we don't handle confidential data in
  99          * mandoc in the first place, simply free the memory
 100          * without clearing it.
 101          */
 102
 103         free(ptr);
 104
 105         return newptr;
 106 }
 107
 108 #endif /* !HAVE_RECALLOCARRAY */