1 /*
2  * Copyright (c) 2008, 2017 Otto Moerbeek <otto@drijf.net>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include "../config.h"
18 
19 #include <errno.h>
20 #include <stdlib.h>
21 #include <stdint.h>
22 #include <string.h>
23 #include <unistd.h>
24 
25 /*
26  * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
27  * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
28  */
29 #define MUL_NO_OVERFLOW ((size_t)1 << (sizeof(size_t) * 4))
30 
31 /*
32  * Even though specified in POSIX, the PAGESIZE and PAGE_SIZE
33  * macros have very poor portability.  Since we only use this
34  * to avoid free() overhead for small shrinking, simply pick
35  * an arbitrary number.
36  */
37 #define getpagesize()	(1UL << 12)
38 
39 void *
40 recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
41 {
42 	size_t oldsize, newsize;
43 	void *newptr;
44 
45 	if (ptr == NULL)
46 		return calloc(newnmemb, size);
47 
48 	if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
49 	    newnmemb > 0 && SIZE_MAX / newnmemb < size) {
50 		errno = ENOMEM;
51 		return NULL;
52 	}
53 	newsize = newnmemb * size;
54 
55 	if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
56 	    oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
57 		errno = EINVAL;
58 		return NULL;
59 	}
60 	oldsize = oldnmemb * size;
61 
62 	/*
63 	 * Don't bother too much if we're shrinking just a bit,
64 	 * we do not shrink for series of small steps, oh well.
65 	 */
66 	if (newsize <= oldsize) {
67 		size_t d = oldsize - newsize;
68 
69 		if (d < oldsize / 2 && d < getpagesize()) {
70 			memset((char *)ptr + newsize, 0, d);
71 			return ptr;
72 		}
73 	}
74 
75 	newptr = malloc(newsize);
76 	if (newptr == NULL)
77 		return NULL;
78 
79 	if (newsize > oldsize) {
80 		memcpy(newptr, ptr, oldsize);
81 		memset((char *)newptr + oldsize, 0, newsize - oldsize);
82 	} else
83 		memcpy(newptr, ptr, newsize);
84 
85 	explicit_bzero(ptr, oldsize);
86 	free(ptr);
87 
88 	return newptr;
89 }