/* $Id: bs3-cmn-MemMove.c $ */
/** @file
 * BS3Kit - Bs3MemMove
 */

/*
 * Copyright (C) 2007-2019 Oracle Corporation
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
 * VirtualBox OSE distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 */

#include "bs3kit-template-header.h"

#undef Bs3MemMove
BS3_CMN_DEF(void BS3_FAR *, Bs3MemMove,(void BS3_FAR *pvDst, const void BS3_FAR *pvSrc, size_t cbToCopy))
{
    size_t          cLargeRounds;
    BS3CVPTRUNION   uSrc;
    BS3PTRUNION     uDst;
    uSrc.pv = pvSrc;
    uDst.pv = pvDst;

    /* We don't care about segment wrapping here. */
    if ((uintptr_t)pvDst > (uintptr_t)pvSrc + cbToCopy)
    {
        /* Reverse copy. */
        uSrc.pb += cbToCopy;
        uDst.pb += cbToCopy;

        cLargeRounds = cbToCopy / sizeof(*uSrc.pcb);
        while (cLargeRounds-- > 0)
        {
            size_t uTmp = *--uSrc.pcb;
            *--uDst.pcb = uTmp;
        }

        cbToCopy %= sizeof(*uSrc.pcb);
        while (cbToCopy-- > 0)
        {
            uint8_t b = *--uSrc.pb;
            *--uDst.pb = b;
        }
    }
    else
    {
        /* Forward copy. */
        cLargeRounds = cbToCopy / sizeof(*uSrc.pcb);
        while (cLargeRounds-- > 0)
        {
            size_t uTmp = *uSrc.pcb++;
            *uDst.pcb++ = uTmp;
        }

        cbToCopy %= sizeof(*uSrc.pcb);
        while (cbToCopy-- > 0)
        {
            uint8_t b = *uSrc.pb++;
            *uDst.pb++ = b;
        }
    }
    return pvDst;
}