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c5d9d3bb | 1 | /* Append a null-terminated string to another string, with length checking. |
896014f4 DL |
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 | |
d62a17ae | 17 | * <http://www.gnu.org/licenses/>. |
896014f4 | 18 | */ |
c5d9d3bb DL |
19 | |
20 | /* adapted for Quagga from glibc patch submission originally from | |
21 | * Florian Weimer <fweimer@redhat.com>, 2016-05-18 */ | |
22 | ||
23 | #include <stdint.h> | |
24 | #include <string.h> | |
25 | ||
26 | #include "config.h" | |
27 | ||
28 | #ifndef HAVE_STRLCAT | |
29 | #undef strlcat | |
30 | ||
d62a17ae | 31 | size_t strlcat(char *__restrict dest, const char *__restrict src, size_t size); |
c5d9d3bb | 32 | |
d62a17ae | 33 | size_t strlcat(char *__restrict dest, const char *__restrict src, size_t size) |
c5d9d3bb | 34 | { |
d62a17ae | 35 | size_t src_length = strlen(src); |
c5d9d3bb | 36 | |
d62a17ae | 37 | /* Our implementation strlcat supports dest == NULL if size == 0 |
38 | (for consistency with snprintf and strlcpy), but strnlen does | |
39 | not, so we have to cover this case explicitly. */ | |
40 | if (size == 0) | |
41 | return src_length; | |
c5d9d3bb | 42 | |
d62a17ae | 43 | size_t dest_length = strnlen(dest, size); |
44 | if (dest_length != size) { | |
45 | /* Copy at most the remaining number of characters in the | |
46 | destination buffer. Leave for the NUL terminator. */ | |
47 | size_t to_copy = size - dest_length - 1; | |
48 | /* But not more than what is available in the source string. */ | |
49 | if (to_copy > src_length) | |
50 | to_copy = src_length; | |
c5d9d3bb | 51 | |
d62a17ae | 52 | char *target = dest + dest_length; |
53 | memcpy(target, src, to_copy); | |
54 | target[to_copy] = '\0'; | |
55 | } | |
c5d9d3bb | 56 | |
d62a17ae | 57 | /* If the sum wraps around, we have more than SIZE_MAX + 2 bytes in |
58 | the two input strings (including both null terminators). If each | |
59 | byte in the address space can be assigned a unique size_t value | |
60 | (which the static_assert checks), then by the pigeonhole | |
61 | principle, the two input strings must overlap, which is | |
62 | undefined. */ | |
c5d9d3bb | 63 | #if __STDC_VERSION__ >= 201112L |
d62a17ae | 64 | _Static_assert(sizeof(uintptr_t) == sizeof(size_t), |
65 | "theoretical maximum object size covers address space"); | |
c5d9d3bb | 66 | #endif |
d62a17ae | 67 | return dest_length + src_length; |
c5d9d3bb DL |
68 | } |
69 | #endif /* HAVE_STRLCAT */ |