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memcpy.c

/*-
 * 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.
 * 4. 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.
 */

/* $FreeBSD: src/sys/powerpc/powerpc/bcopy.c,v 1.5.24.1 2010/02/10 00:26:20 kensmith Exp $ */

#include <string.h>

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

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

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

      dst = dst0;
      src = src0;

      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 = (int)src;     /* only need low bits */

            if ((t | (int)dst) & wmask) {
                  /*
                   * Try to align operands.  This cannot be done
                   * unless the low bits match.
                   */
                  if ((t ^ (int)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 = *(const 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 = (int)src;

            if ((t | (int)dst) & wmask) {
                  if ((t ^ (int)dst) & wmask || length <= wsize) {
                        t = length;
                  } else {
                        t &= wmask;
                  }

                  length -= t;
                  TLOOP1(*--dst = *--src);
            }
            t = length / wsize;
            TLOOP(src -= wsize; dst -= wsize;
                *(word *)dst = *(const word *)src);
            t = length & wmask;
            TLOOP(*--dst = *--src);
      }
done:
      return (dst0);
}

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