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/* Append a null-terminated string to another string, with length checking.
Copyright (C) 2023-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <stdint.h>
#include <string.h>
size_t
__strlcat (char *__restrict dest, const char *__restrict src, size_t size)
{
size_t src_length = strlen (src);
/* Our implementation strlcat supports dest == NULL if size == 0
(for consistency with snprintf and strlcpy), but strnlen does
not, so we have to cover this case explicitly. */
if (size == 0)
return src_length;
size_t dest_length = __strnlen (dest, size);
if (dest_length != size)
{
/* Copy at most the remaining number of characters in the
destination buffer. Leave for the NUL terminator. */
size_t to_copy = size - dest_length - 1;
/* But not more than what is available in the source string. */
if (to_copy > src_length)
to_copy = src_length;
char *target = dest + dest_length;
memcpy (target, src, to_copy);
target[to_copy] = '\0';
}
/* If the sum wraps around, we have more than SIZE_MAX + 2 bytes in
the two input strings (including both null terminators). If each
byte in the address space can be assigned a unique size_t value
(which the static_assert checks), then by the pigeonhole
principle, the two input strings must overlap, which is
undefined. */
_Static_assert (sizeof (uintptr_t) == sizeof (size_t),
"theoretical maximum object size covers address space");
return dest_length + src_length;
}
libc_hidden_def (__strlcat)
weak_alias (__strlcat, strlcat)
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