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/*
Copyright (c) 1994 Cygnus Support.
All rights reserved.
Redistribution and use in source and binary forms are permitted
provided that the above copyright notice and this paragraph are
duplicated in all such forms and that any documentation,
and/or other materials related to such
distribution and use acknowledge that the software was developed
at Cygnus Support, Inc. Cygnus Support, Inc. may not be used to
endorse or promote products derived from this software without
specific prior written permission.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
/*
FUNCTION
<<strncat>>---concatenate strings
INDEX
strncat
SYNOPSIS
#include <string.h>
char *strncat(char *restrict <[dst]>, const char *restrict <[src]>,
size_t <[length]>);
DESCRIPTION
<<strncat>> appends not more than <[length]> characters from
the string pointed to by <[src]> (including the terminating
null character) to the end of the string pointed to by
<[dst]>. The initial character of <[src]> overwrites the null
character at the end of <[dst]>. A terminating null character
is always appended to the result
WARNINGS
Note that a null is always appended, so that if the copy is
limited by the <[length]> argument, the number of characters
appended to <[dst]> is <<n + 1>>.
RETURNS
This function returns the initial value of <[dst]>
PORTABILITY
<<strncat>> is ANSI C.
<<strncat>> requires no supporting OS subroutines.
QUICKREF
strncat ansi pure
*/
#include <string.h>
#include <limits.h>
#include "local.h"
#undef strncat
char *
strncat(char * __restrict s1, const char * __restrict s2, size_t n)
{
#if defined(__PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) \
|| defined(_PICOLIBC_NO_OUT_OF_BOUNDS_READS)
char *s = s1;
while (*s1)
s1++;
while (n-- != 0 && (*s1++ = *s2++)) {
if (n == 0)
*s1 = '\0';
}
return s;
#else
char *s = s1;
/* Skip unaligned memory in s1. */
while (UNALIGNED_X(s1) && *s1)
s1++;
if (*s1) {
/* Skip over the aligned data in s1 as quickly as possible. */
unsigned long *aligned_s1 = (unsigned long *)s1;
while (!DETECT_NULL(*aligned_s1))
aligned_s1++;
s1 = (char *)aligned_s1;
/* Find string terminator. */
while (*s1)
s1++;
}
/* s1 now points to the its trailing null character, now copy
up to N bytes from S2 into S1 stopping if a NULL is encountered
in S2.
It is not safe to use strncpy here since it copies EXACTLY N
characters, NULL padding if necessary. */
while (n-- != 0 && (*s1++ = *s2++)) {
if (n == 0)
*s1 = '\0';
}
return s;
#endif /* not __PREFER_SIZE_OVER_SPEED */
}
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