1 /*	$OpenBSD: recallocarray.c,v 1.2 2021/03/18 11:16:58 claudio 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 "../config.h"
19 
20 #include <errno.h>
21 #include <stdlib.h>
22 #include <stdint.h>
23 #include <string.h>
24 #include <unistd.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 void *
41 recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
42 {
43 	size_t oldsize, newsize;
44 	void *newptr;
45 
46 	if (ptr == NULL)
47 		return calloc(newnmemb, size);
48 
49 	if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
50 	    newnmemb > 0 && SIZE_MAX / newnmemb < size) {
51 		errno = ENOMEM;
52 		return NULL;
53 	}
54 	newsize = newnmemb * size;
55 
56 	if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
57 	    oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
58 		errno = EINVAL;
59 		return NULL;
60 	}
61 	oldsize = oldnmemb * size;
62 
63 	/*
64 	 * Don't bother too much if we're shrinking just a bit,
65 	 * we do not shrink for series of small steps, oh well.
66 	 */
67 	if (newsize <= oldsize) {
68 		size_t d = oldsize - newsize;
69 
70 		if (d < oldsize / 2 && d < (size_t)getpagesize()) {
71 			memset((char *)ptr + newsize, 0, d);
72 			return ptr;
73 		}
74 	}
75 
76 	newptr = malloc(newsize);
77 	if (newptr == NULL)
78 		return NULL;
79 
80 	if (newsize > oldsize) {
81 		memcpy(newptr, ptr, oldsize);
82 		memset((char *)newptr + oldsize, 0, newsize - oldsize);
83 	} else
84 		memcpy(newptr, ptr, newsize);
85 
86 	explicit_bzero(ptr, oldsize);
87 	free(ptr);
88 
89 	return newptr;
90 }