compat_recallocarray.c

   1 /*      $Id: compat_recallocarray.c,v 1.2 2020/06/15 01:37:15 schwarze Exp $ */
   2 /*      $OpenBSD: recallocarray.c,v 1.1 2017/03/06 18:44:21 otto Exp $  */
   3 /*
   4  * Copyright (c) 2008, 2017 Otto Moerbeek <otto@drijf.net>
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18 #include "config.h"
  19
  20 #include <sys/types.h>
  21 #include <errno.h>
  22 #include <stdlib.h>
  23 #include <stdint.h>
  24 #include <string.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 /*
  33  * Even though specified in POSIX, the PAGESIZE and PAGE_SIZE
  34  * macros have very poor portability.  Since we only use this
  35  * to avoid free() overhead for small shrinking, simply pick
  36  * an arbitrary number.
  37  */
  38 #define getpagesize()   (1UL << 12)
  39
  40
  41 void *
  42 recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
  43 {
  44         size_t oldsize, newsize;
  45         void *newptr;
  46
  47         if (ptr == NULL)
  48                 return calloc(newnmemb, size);
  49
  50         if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
  51             newnmemb > 0 && SIZE_MAX / newnmemb < size) {
  52                 errno = ENOMEM;
  53                 return NULL;
  54         }
  55         newsize = newnmemb * size;
  56
  57         if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
  58             oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
  59                 errno = EINVAL;
  60                 return NULL;
  61         }
  62         oldsize = oldnmemb * size;
  63
  64         /*
  65          * Don't bother too much if we're shrinking just a bit,
  66          * we do not shrink for series of small steps, oh well.
  67          */
  68         if (newsize <= oldsize) {
  69                 size_t d = oldsize - newsize;
  70
  71                 if (d < oldsize / 2 && d < getpagesize()) {
  72                         memset((char *)ptr + newsize, 0, d);
  73                         return ptr;
  74                 }
  75         }
  76
  77         newptr = malloc(newsize);
  78         if (newptr == NULL)
  79                 return NULL;
  80
  81         if (newsize > oldsize) {
  82                 memcpy(newptr, ptr, oldsize);
  83                 memset((char *)newptr + oldsize, 0, newsize - oldsize);
  84         } else
  85                 memcpy(newptr, ptr, newsize);
  86
  87         /*
  88          * At this point, the OpenBSD implementation calls
  89          * explicit_bzero() on the old memory before it is
  90          * freed.  Since explicit_bzero() is hard to implement
  91          * portably and we don't handle confidential data in
  92          * mandoc in the first place, simply free the memory
  93          * without clearing it.
  94          */
  95
  96         free(ptr);
  97
  98         return newptr;
  99 }