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 *
recallocarray(void * ptr,size_t oldnmemb,size_t newnmemb,size_t size)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 }
100