/*
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
	<<strcat>>---concatenate strings

INDEX
	strcat

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

DESCRIPTION
	<<strcat>> appends a copy of 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]>.

RETURNS
	This function returns the initial value of <[dst]>

PORTABILITY
<<strcat>> is ANSI C.

<<strcat>> requires no supporting OS subroutines.

QUICKREF
	strcat ansi pure
*/

#include <string.h>
#include <limits.h>
#include <stdint.h>

/* Nonzero if X is aligned on a "long" boundary.  */
#define ALIGNED(X) \
  (((uintptr_t)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


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

#undef strcat

char *
strcat (char *__restrict s1,
	const char *__restrict s2)
{
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) || \
    defined(PICOLIBC_NO_OUT_OF_BOUNDS_READS)
  char *s = s1;

  while (*s1)
    s1++;

  while ((*s1++ = *s2++))
    ;
  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, we can
     just use strcpy to do the work for us now.

     ?!? We might want to just include strcpy here.
     Also, this will cause many more unaligned string copies because
     s1 is much less likely to be aligned.  I don't know if its worth
     tweaking strcpy to handle this better.  */
  strcpy (s1, s2);

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