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/*

FUNCTION

        <<memccpy>>---copy memory regions with end-token check

ANSI_SYNOPSIS

        #include <string.h>

        void* memccpy(void *<[out]>, const void *<[in]>,

                      int <[endchar]>, size_t <[n]>);

TRAD_SYNOPSIS

        void *memccpy(<[out]>, <[in]>, <[endchar]>, <[n]>

        void *<[out]>;

        void *<[in]>;

        int <[endchar]>;

        size_t <[n]>;

DESCRIPTION

        This function copies up to <[n]> bytes from the memory region

        pointed to by <[in]> to the memory region pointed to by

        <[out]>.  If a byte matching the <[endchar]> is encountered,

        the byte is copied and copying stops.

        If the regions overlap, the behavior is undefined.

RETURNS

        <<memccpy>> returns a pointer to the first byte following the

        <[endchar]> in the <[out]> region.  If no byte matching

        <[endchar]> was copied, then <<NULL>> is returned.

PORTABILITY

<<memccpy>> is a GNU extension.

<<memccpy>> requires no supporting OS subroutines.

        */

#include <_ansi.h>

#include <stddef.h>

#include <string.h>

#include <limits.h>

/* 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)))

/* How many bytes are copied each iteration of the word copy loop.  */

#define LITTLEBLOCKSIZE (sizeof (long))

/* Threshhold for punting to the byte copier.  */

#define TOO_SMALL(LEN)  ((LEN) < LITTLEBLOCKSIZE)

/* Macros for detecting endchar */

#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

_PTR

_DEFUN (memccpy, (dst0, src0, endchar, len0),

        _PTR dst0 _AND

        _CONST _PTR src0 _AND

        int endchar0 _AND

        size_t len0)

{

#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)

  _PTR ptr = NULL;

  char *dst = (char *) dst0;

  char *src = (char *) src0;

  char endchar = endchar0 & 0xff;

  while (len0--)

    {

      if ((*dst++ = *src++) == endchar)

        {

          ptr = dst;

          break;

        }

    }

  return ptr;

#else

  _PTR ptr = NULL;

  char *dst = dst0;

  _CONST char *src = src0;

  long *aligned_dst;

  _CONST long *aligned_src;

  int   len =  len0;

  char endchar = endchar0 & 0xff;

  /* If the size is small, or either SRC or DST is unaligned,

     then punt into the byte copy loop.  This should be rare.  */

  if (!TOO_SMALL(len) && !UNALIGNED (src, dst))

    {

      int i;

      unsigned long mask = 0;

      aligned_dst = (long*)dst;

      aligned_src = (long*)src;

      /* The fast code reads the ASCII one word at a time and only

         performs the bytewise search on word-sized segments if they

         contain the search character, which is detected by XORing

         the word-sized segment with a word-sized block of the search

         character and then detecting for the presence of NULL in the

         result.  */

      for (i = 0; i < LITTLEBLOCKSIZE; i++)

        mask = (mask << 8) + endchar;

      /* Copy one long word at a time if possible.  */

      while (len >= LITTLEBLOCKSIZE)

        {

          unsigned long buffer = (unsigned long)(*aligned_src);

          buffer ^=  mask;

          if (DETECTNULL (buffer))

            break; /* endchar is found, go byte by byte from here */

          *aligned_dst++ = *aligned_src++;

          len -= LITTLEBLOCKSIZE;

        }

       /* Pick up any residual with a byte copier.  */

      dst = (char*)aligned_dst;

      src = (char*)aligned_src;

    }

  while (len--)

    {

      if ((*dst++ = *src++) == endchar)

        {

          ptr = dst;

          break;

        }

    }

  return ptr;

#endif /* not PREFER_SIZE_OVER_SPEED */

}