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/*
FUNCTION
<<stpncpy>>---counted copy string returning a pointer to its end
INDEX
stpncpy
SYNOPSIS
#include <string.h>
char *stpncpy(char *restrict <[dst]>, const char *restrict <[src]>,
size_t <[length]>);
DESCRIPTION
<<stpncpy>> copies not more than <[length]> characters from the
the string pointed to by <[src]> (including the terminating
null character) to the array pointed to by <[dst]>. If the
string pointed to by <[src]> is shorter than <[length]>
characters, null characters are appended to the destination
array until a total of <[length]> characters have been
written.
RETURNS
This function returns a pointer to the end of the destination string,
thus pointing to the trailing '\0', or, if the destination string is
not null-terminated, pointing to dst + n.
PORTABILITY
<<stpncpy>> is a GNU extension, candidate for inclusion into POSIX/SUSv4.
<<stpncpy>> requires no supporting OS subroutines.
QUICKREF
stpncpy gnu
*/
#include <string.h>
#include <limits.h>
/*SUPPRESS 560*/
/*SUPPRESS 530*/
/* Nonzero if either X or Y is not aligned on a "long" boundary. */
#define UNALIGNED(X, Y) \
(((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
#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
#define TOO_SMALL(LEN) ((LEN) < sizeof (long))
char *
stpncpy (char *__restrict dst,
const char *__restrict src,
size_t count)
{
char *ret = NULL;
#if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
long *aligned_dst;
const long *aligned_src;
/* If SRC and DEST is aligned and count large enough, then copy words. */
if (!UNALIGNED (src, dst) && !TOO_SMALL (count))
{
aligned_dst = (long*)dst;
aligned_src = (long*)src;
/* SRC and DEST are both "long int" aligned, try to do "long int"
sized copies. */
while (count >= sizeof (long int) && !DETECTNULL(*aligned_src))
{
count -= sizeof (long int);
*aligned_dst++ = *aligned_src++;
}
dst = (char*)aligned_dst;
src = (char*)aligned_src;
}
#endif /* not PREFER_SIZE_OVER_SPEED */
while (count > 0)
{
--count;
if ((*dst++ = *src++) == '\0')
{
ret = dst - 1;
break;
}
}
while (count-- > 0)
*dst++ = '\0';
return ret ? ret : dst;
}
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