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git.proxmox.com Git - mirror_frr.git/blob - lib/strlcat.c
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.
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.
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.
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/>. */
19 /* adapted for Quagga from glibc patch submission originally from
20 * Florian Weimer <fweimer@redhat.com>, 2016-05-18 */
31 strlcat (char *__restrict dest
, const char *__restrict src
, size_t size
);
34 strlcat (char *__restrict dest
, const char *__restrict src
, size_t size
)
36 size_t src_length
= strlen (src
);
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. */
44 size_t dest_length
= strnlen (dest
, size
);
45 if (dest_length
!= size
)
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
)
54 char *target
= dest
+ dest_length
;
55 memcpy (target
, src
, to_copy
);
56 target
[to_copy
] = '\0';
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
65 #if __STDC_VERSION__ >= 201112L
66 _Static_assert (sizeof (uintptr_t) == sizeof (size_t),
67 "theoretical maximum object size covers address space");
69 return dest_length
+ src_length
;
71 #endif /* HAVE_STRLCAT */