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60 lines
2.3 KiB
C
60 lines
2.3 KiB
C
/* Append a null-terminated string to another string, with length checking.
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Copyright (C) 2023-2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <stdint.h>
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#include <string.h>
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size_t
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__strlcat (char *__restrict dest, const char *__restrict src, size_t size)
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{
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size_t src_length = strlen (src);
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/* Our implementation strlcat supports dest == NULL if size == 0
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(for consistency with snprintf and strlcpy), but strnlen does
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not, so we have to cover this case explicitly. */
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if (size == 0)
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return src_length;
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size_t dest_length = __strnlen (dest, size);
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if (dest_length != size)
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{
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/* Copy at most the remaining number of characters in the
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destination buffer. Leave for the NUL terminator. */
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size_t to_copy = size - dest_length - 1;
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/* But not more than what is available in the source string. */
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if (to_copy > src_length)
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to_copy = src_length;
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char *target = dest + dest_length;
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memcpy (target, src, to_copy);
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target[to_copy] = '\0';
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}
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/* If the sum wraps around, we have more than SIZE_MAX + 2 bytes in
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the two input strings (including both null terminators). If each
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byte in the address space can be assigned a unique size_t value
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(which the static_assert checks), then by the pigeonhole
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principle, the two input strings must overlap, which is
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undefined. */
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_Static_assert (sizeof (uintptr_t) == sizeof (size_t),
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"theoretical maximum object size covers address space");
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return dest_length + src_length;
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}
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libc_hidden_def (__strlcat)
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weak_alias (__strlcat, strlcat)
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