/*      $OpenBSD: memcpy.c,v 1.4 2017/11/29 05:13:57 guenther Exp $ */
/*-
 * 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.
 */

#include <string.h>
#include <stdlib.h>
#include <syslog.h>

/*
 * 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)

static const char backwards_msg[] = ": backwards memcpy";

/*
 * Copy a block of memory, not handling overlap.
 */
void *
memcpy(void *dst0, const void *src0, size_t length)
{
        char *dst = dst0;
        const char *src = src0;
        size_t t;

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

        if ((dst < src && dst + length > src) ||
            (src < dst && src + length > dst)) {
                char buf[1024];

                /* <10> is LOG_CRIT */
                strlcpy(buf, "<10>", sizeof buf);

                /* Make sure progname does not fill the whole buffer */
                strlcat(buf, __progname, sizeof(buf) - sizeof backwards_msg);
                strlcat(buf, backwards_msg, sizeof buf);

                sendsyslog(buf, strlen(buf), LOG_CONS);
                abort();
        }

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

        /*
         * 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++);
done:
        return (dst0);
}
DEF_BUILTIN(memcpy);