linux-sgx-trts-modified/sdk/tlibc/string/bcopy.c

/*  $OpenBSD: bcopy.c,v 1.7 2015/08/31 02:53:57 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>

/*
 * 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)

#ifdef MEMPCPY
void *
mempcpy(void *dst0, const void *src0, size_t length)
#else
/*
 * Copy a block of memory, handling overlap.
 */
void
bcopy(const void *src0, void *dst0, size_t length)
#endif
{
    char *dst = (char *)dst0;
    const char *src = (const char *)src0;
    size_t t;

#ifdef MEMPCPY
    size_t len = length;
#endif

    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:
#if defined(MEMPCPY)
    return ((void *)(((char *)dst0) + len));
#else
    return;
#endif
}