bcopy.c

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/*-
 * SPDX-License-Identifier: BSD-3-Clause
 * 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)
#if 0
static char *sccsid = "from: @(#)bcopy.c      5.11 (Berkeley) 6/21/91";
#endif
#if 0
static char *rcsid = "$NetBSD: bcopy.c,v 1.2 1997/04/16 22:09:41 thorpej Exp $";
#endif
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include <sys/param.h>
#ifdef _KERNEL
#include <sys/systm.h>
#else
#include <string.h>
#endif
 
#undef memcpy
#undef memmove
 
/*
 * 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)
 
/*
 * 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 = (size_t)src;        /* only need low bits */
 
                if ((t | (uintptr_t)dst) & wmask) {
                        /*
                         * Try to align operands.  This cannot be done
                         * unless the low bits match.
                         */
                        if ((t ^ (uintptr_t)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 = (uintptr_t)src;
 
                if ((t | (uintptr_t)dst) & wmask) {
                        if ((t ^ (uintptr_t)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);
}
 
__strong_reference(memcpy, memmove);