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1 | /* Append a null-terminated string to another string, with length checking. |
2 | Copyright (C) 2016 Free Software Foundation, Inc. | |
3 | This file is part of the GNU C Library. | |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
17 | <http://www.gnu.org/licenses/>. */ | |
18 | ||
19 | /* adapted for Quagga from glibc patch submission originally from | |
20 | * Florian Weimer <fweimer@redhat.com>, 2016-05-18 */ | |
21 | ||
22 | #include <stdint.h> | |
23 | #include <string.h> | |
24 | ||
25 | #include "config.h" | |
26 | ||
27 | #ifndef HAVE_STRLCAT | |
28 | #undef strlcat | |
29 | ||
30 | size_t | |
31 | strlcat (char *__restrict dest, const char *__restrict src, size_t size); | |
32 | ||
33 | size_t | |
34 | strlcat (char *__restrict dest, const char *__restrict src, size_t size) | |
35 | { | |
36 | size_t src_length = strlen (src); | |
37 | ||
38 | /* Our implementation strlcat supports dest == NULL if size == 0 | |
39 | (for consistency with snprintf and strlcpy), but strnlen does | |
40 | not, so we have to cover this case explicitly. */ | |
41 | if (size == 0) | |
42 | return src_length; | |
43 | ||
44 | size_t dest_length = strnlen (dest, size); | |
45 | if (dest_length != size) | |
46 | { | |
47 | /* Copy at most the remaining number of characters in the | |
48 | destination buffer. Leave for the NUL terminator. */ | |
49 | size_t to_copy = size - dest_length - 1; | |
50 | /* But not more than what is available in the source string. */ | |
51 | if (to_copy > src_length) | |
52 | to_copy = src_length; | |
53 | ||
54 | char *target = dest + dest_length; | |
55 | memcpy (target, src, to_copy); | |
56 | target[to_copy] = '\0'; | |
57 | } | |
58 | ||
59 | /* If the sum wraps around, we have more than SIZE_MAX + 2 bytes in | |
60 | the two input strings (including both null terminators). If each | |
61 | byte in the address space can be assigned a unique size_t value | |
62 | (which the static_assert checks), then by the pigeonhole | |
63 | principle, the two input strings must overlap, which is | |
64 | undefined. */ | |
65 | #if __STDC_VERSION__ >= 201112L | |
66 | _Static_assert (sizeof (uintptr_t) == sizeof (size_t), | |
67 | "theoretical maximum object size covers address space"); | |
68 | #endif | |
69 | return dest_length + src_length; | |
70 | } | |
71 | #endif /* HAVE_STRLCAT */ |