/* $Id: kHlpMemPMove.c 29 2009-07-01 20:30:29Z bird $ */
/** @file
 * kHlpString - kHlpMemPMove.
 */

/*
 * Copyright (c) 2006-2007 Knut St. Osmundsen <bird-kStuff-spamix@anduin.net>
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

/*******************************************************************************
*   Header Files                                                               *
*******************************************************************************/
#include <k/kHlpString.h>


KHLP_DECL(void *) kHlpMemPMove(void *pv1, const void *pv2, KSIZE cb)
{
    union
    {
        void *pv;
        KU8 *pb;
        KUPTR *pu;
    } u1;
    union
    {
        const void *pv;
        volatile KU8 *pb;
        volatile KUPTR *pu;
    } u2;

    u1.pv = pv1;
    u2.pv = pv2;

    if ((KUPTR)u1.pb <= (KUPTR)u2.pb)
    {
        /* forwards copy */
        if (cb >= 32)
        {
            while (cb > sizeof(KUPTR))
            {
                KUPTR u = *u2.pu++;
                *u1.pu++ = u;
                cb -= sizeof(KUPTR);
            }
        }

        while (cb-- > 0)
        {
            KU8 b = *u2.pb++;
            *u1.pb++ = b;
        }

        return u1.pb;
    }

    /* backwards copy */
    u1.pb += cb;
    u2.pb += cb;

    if (cb >= 32)
    {
        while (cb > sizeof(KUPTR))
        {
            KUPTR u = *--u2.pu;
            *--u1.pu = u;
            cb -= sizeof(KUPTR);
        }
    }

    while (cb-- > 0)
    {
        KU8 b = *--u2.pb;
        *--u1.pb = b;
    }

    return (KU8 *)pv1 + cb;
}