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/*
FUNCTION
	<<strncpy>>---counted copy string
 
INDEX
	strncpy
 
ANSI_SYNOPSIS
	#include <string.h>
	char *strncpy(char *<[dst]>, const char *<[src]>, size_t <[length]>);
 
TRAD_SYNOPSIS
	#include <string.h>
	char *strncpy(<[dst]>, <[src]>, <[length]>)
	char *<[dst]>;
	char *<[src]>;
	size_t <[length]>;
 
DESCRIPTION
	<<strncpy>> 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 the initial value of <[dst]>.
 
PORTABILITY
<<strncpy>> is ANSI C.
 
<<strncpy>> requires no supporting OS subroutines.
 
QUICKREF
	strncpy ansi pure
*/
 
#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 *
_DEFUN (strncpy, (dst0, src0),
	char *dst0 _AND
	_CONST char *src0 _AND
	size_t count)
{
#ifdef PREFER_SIZE_OVER_SPEED
  char *dscan;
  _CONST char *sscan;
 
  dscan = dst0;
  sscan = src0;
  while (count > 0)
    {
      --count;
      if ((*dscan++ = *sscan++) == '\0')
	break;
    }
  while (count-- > 0)
    *dscan++ = '\0';
 
  return dst0;
#else
  char *dst = dst0;
  _CONST char *src = src0;
  long *aligned_dst;
  _CONST long *aligned_src;
 
  /* If SRC or DEST is unaligned, then copy bytes.  */
  if (TOO_SMALL (count) || UNALIGNED (src, dst))
    {
      while (count > 0)
	{
	  --count;
	  if ((*dst++ = *src++) == '\0')
	    break;
	}
 
      while (count -- > 0)
	*dst++ = '\0';
 
      return dst0;
    }
 
  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;
 
  while (count > 0)
    {
      --count;
      if ((*dst++ = *src++) == '\0')
	break;
    }
 
  while (count-- > 0)
    *dst++ = '\0';
 
  return dst0;
#endif /* not PREFER_SIZE_OVER_SPEED */
}