116 lines
2.5 KiB
C
116 lines
2.5 KiB
C
|
/*
|
||
|
|
FUNCTION
|
||
|
|
<<strncat>>---concatenate strings
|
||
|
|
|
||
|
|
INDEX
|
||
|
|
strncat
|
||
|
|
|
||
|
|
ANSI_SYNOPSIS
|
||
|
|
#include <string.h>
|
||
|
|
char *strncat(char *<[dst]>, const char *<[src]>, size_t <[length]>);
|
||
|
|
|
||
|
|
TRAD_SYNOPSIS
|
||
|
|
#include <string.h>
|
||
|
|
char *strncat(<[dst]>, <[src]>, <[length]>)
|
||
|
|
char *<[dst]>;
|
||
|
|
char *<[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>
|
||
|
|
|
||
|
|
/* Nonzero if X is aligned on a "long" boundary. */
|
||
|
|
#define ALIGNED(X) \
|
||
|
|
(((long)X & (sizeof (long) - 1)) == 0)
|
||
|
|
|
||
|
|
#if LONG_MAX == 2147483647L
|
||
|
|
#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
|
||
|
|
#else
|
||
|
|
#if LONG_MAX == 9223372036854775807L
|
||
|
|
/* Nonzero if X (a long int) contains a NULL byte. */
|
||
|
|
#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
|
||
|
|
#else
|
||
|
|
#error long int is not a 32bit or 64bit type.
|
||
|
|
#endif
|
||
|
|
#endif
|
||
|
|
|
||
|
|
#ifndef DETECTNULL
|
||
|
|
#error long int is not a 32bit or 64bit byte
|
||
|
|
#endif
|
||
|
|
|
||
|
|
char *
|
||
|
|
_DEFUN (strncat, (s1, s2, n),
|
||
|
|
char *s1 _AND
|
||
|
|
_CONST char *s2 _AND
|
||
|
|
size_t n)
|
||
|
|
{
|
||
|
|
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
|
||
|
|
char *s = s1;
|
||
|
|
|
||
|
|
while (*s1)
|
||
|
|
s1++;
|
||
|
|
while (n-- != 0 && (*s1++ = *s2++))
|
||
|
|
{
|
||
|
|
if (n == 0)
|
||
|
|
*s1 = '\0';
|
||
|
|
}
|
||
|
|
|
||
|
|
return s;
|
||
|
|
#else
|
||
|
|
char *s = s1;
|
||
|
|
|
||
|
|
/* Skip over the data in s1 as quickly as possible. */
|
||
|
|
if (ALIGNED (s1))
|
||
|
|
{
|
||
|
|
unsigned long *aligned_s1 = (unsigned long *)s1;
|
||
|
|
while (!DETECTNULL (*aligned_s1))
|
||
|
|
aligned_s1++;
|
||
|
|
|
||
|
|
s1 = (char *)aligned_s1;
|
||
|
|
}
|
||
|
|
|
||
|
|
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 */
|
||
|
|
}
|