/* $Id: memmove.c,v 1.10 2012/10/22 15:15:58 karls Exp $ */

#ifdef HAVE_CONFIG_H
#include "autoconf.h"
#endif /* HAVE_CONFIG_H */

#include "osdep.h"

/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char *rcsid = "$OpenBSD: bcopy.c,v 1.2 1996/08/19 08:33:58 tholo Exp $";
#endif /* LIBC_SCCS and not lint */

/*
 * sizeof(word) MUST BE A POWER OF TWO
 * SO THAT wmask BELOW IS ALL ONES
 */
typedef   long word;      /* "word" used for optimal copy speed */

#define   wsize   sizeof(word)
#define   wmask   (wsize - 1)

#undef memmove

/*
 * Copy a block of memory, handling overlap.
 * This is the routine that actually implements
 * (the portable versions of) bcopy, memcpy, and memmove.
 */
void *
memmove(dst0, src0, length)
   void *dst0;
   const void *src0;
   register size_t length;
{
   register char *dst = dst0;
   register const char *src = src0;
   register size_t t;

   if (length == 0 || dst == src)      /* nothing to do */
      goto done;

   /*
    * Macros: loop-t-times; and loop-t-times, t>0
    */
#define   TLOOP(s) if (t) TLOOP1(s)
#define   TLOOP1(s) do { s; } while (--t)

   if ((unsigned long)dst < (unsigned long)src) {
      /*
       * Copy forward.
       */
      t = (long)src;   /* only need low bits */
      if ((t | (long)dst) & wmask) {
         /*
          * Try to align operands.  This cannot be done
          * unless the low bits match.
          */
         if ((t ^ (long)dst) & wmask || length < wsize)
            t = length;
         else
            t = wsize - (t & wmask);
         length -= t;
         TLOOP1(*dst++ = *src++);
      }
      /*
       * Copy whole words, then mop up any trailing bytes.
       */
      t = length / wsize;
      TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
      t = length & wmask;
      TLOOP(*dst++ = *src++);
   } else {
      /*
       * Copy backwards.  Otherwise essentially the same.
       * Alignment works as before, except that it takes
       * (t&wmask) bytes to align, not wsize-(t&wmask).
       */
      src += length;
      dst += length;
      t = (long)src;
      if ((t | (long)dst) & wmask) {
         if ((t ^ (long)dst) & wmask || length <= wsize)
            t = length;
         else
            t &= wmask;
         length -= t;
         TLOOP1(*--dst = *--src);
      }
      t = length / wsize;
      TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
      t = length & wmask;
      TLOOP(*--dst = *--src);
   }
done:
   return (dst0);
}
