]>
Commit | Line | Data |
---|---|---|
454a20c8 | 1 | /* Append a null-terminated string to another string, with length checking. |
dff8da6b | 2 | Copyright (C) 2023-2024 Free Software Foundation, Inc. |
454a20c8 FW |
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 | <https://www.gnu.org/licenses/>. */ | |
18 | ||
19 | #include <stdint.h> | |
20 | #include <string.h> | |
21 | ||
22 | size_t | |
23 | __strlcat (char *__restrict dest, const char *__restrict src, size_t size) | |
24 | { | |
25 | size_t src_length = strlen (src); | |
26 | ||
27 | /* Our implementation strlcat supports dest == NULL if size == 0 | |
28 | (for consistency with snprintf and strlcpy), but strnlen does | |
29 | not, so we have to cover this case explicitly. */ | |
30 | if (size == 0) | |
31 | return src_length; | |
32 | ||
33 | size_t dest_length = __strnlen (dest, size); | |
34 | if (dest_length != size) | |
35 | { | |
36 | /* Copy at most the remaining number of characters in the | |
37 | destination buffer. Leave for the NUL terminator. */ | |
38 | size_t to_copy = size - dest_length - 1; | |
39 | /* But not more than what is available in the source string. */ | |
40 | if (to_copy > src_length) | |
41 | to_copy = src_length; | |
42 | ||
43 | char *target = dest + dest_length; | |
44 | memcpy (target, src, to_copy); | |
45 | target[to_copy] = '\0'; | |
46 | } | |
47 | ||
48 | /* If the sum wraps around, we have more than SIZE_MAX + 2 bytes in | |
49 | the two input strings (including both null terminators). If each | |
50 | byte in the address space can be assigned a unique size_t value | |
51 | (which the static_assert checks), then by the pigeonhole | |
52 | principle, the two input strings must overlap, which is | |
53 | undefined. */ | |
54 | _Static_assert (sizeof (uintptr_t) == sizeof (size_t), | |
55 | "theoretical maximum object size covers address space"); | |
56 | return dest_length + src_length; | |
57 | } | |
58 | libc_hidden_def (__strlcat) | |
59 | weak_alias (__strlcat, strlcat) |