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 <errno.h>
19 #include <stdlib.h>
20 #include <stdint.h>
21 #include <string.h>
22 #include <unistd.h>
23 
24 /*
25  * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
26  * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
27  */
28 #define MUL_NO_OVERFLOW ((size_t)1 << (sizeof(size_t) * 4))
29 
30 /*
31  * Even though specified in POSIX, the PAGESIZE and PAGE_SIZE
32  * macros have very poor portability.  Since we only use this
33  * to avoid free() overhead for small shrinking, simply pick
34  * an arbitrary number.
35  */
36 #define getpagesize()	(1UL << 12)
37 
38 void *
39 recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
40 {
41 	size_t oldsize, newsize;
42 	void *newptr;
43 
44 	if (ptr == NULL)
45 		return calloc(newnmemb, size);
46 
47 	if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
48 	    newnmemb > 0 && SIZE_MAX / newnmemb < size) {
49 		errno = ENOMEM;
50 		return NULL;
51 	}
52 	newsize = newnmemb * size;
53 
54 	if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
55 	    oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
56 		errno = EINVAL;
57 		return NULL;
58 	}
59 	oldsize = oldnmemb * size;
60 
61 	/*
62 	 * Don't bother too much if we're shrinking just a bit,
63 	 * we do not shrink for series of small steps, oh well.
64 	 */
65 	if (newsize <= oldsize) {
66 		size_t d = oldsize - newsize;
67 
68 		if (d < oldsize / 2 && d < (size_t)getpagesize()) {
69 			memset((char *)ptr + newsize, 0, d);
70 			return ptr;
71 		}
72 	}
73 
74 	newptr = malloc(newsize);
75 	if (newptr == NULL)
76 		return NULL;
77 
78 	if (newsize > oldsize) {
79 		memcpy(newptr, ptr, oldsize);
80 		memset((char *)newptr + oldsize, 0, newsize - oldsize);
81 	} else
82 		memcpy(newptr, ptr, newsize);
83 
84 	explicit_bzero(ptr, oldsize);
85 	free(ptr);
86 
87 	return newptr;
88 }