/*
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
	<<strncpy>>---counted copy string

INDEX
	strncpy

SYNOPSIS
	#include <string.h>
	char *strncpy(char *restrict <[dst]>, const char *restrict <[src]>,
                      size_t <[length]>);

DESCRIPTION
	<<strncpy>> copies not more than <[length]> characters from
	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>
#include <stdint.h>

/*SUPPRESS 560*/
/*SUPPRESS 530*/

/* Nonzero if either X or Y is not aligned on a "long" boundary.  */
#define UNALIGNED(X, Y) \
  (((uintptr_t)X & (sizeof (long) - 1)) | ((uintptr_t)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))

#undef strncpy

char *
strncpy (char *__restrict dst0,
	const char *__restrict src0,
	size_t count)
{
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) || \
    defined(PICOLIBC_NO_OUT_OF_BOUNDS_READS)
  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 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;
    }

  while (count > 0)
    {
      --count;
      if ((*dst++ = *src++) == '\0')
	break;
    }

  while (count-- > 0)
    *dst++ = '\0';

  return dst0;
#endif /* not PREFER_SIZE_OVER_SPEED */
}
