memmove.c

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/*
 * Copyright 2010 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#include <linux/types.h>
#include <linux/string.h>
#include <linux/module.h>

void *memmove(void *dest, const void *src, size_t n)
{
    if ((const char *)src >= (char *)dest + n
        || (char *)dest >= (const char *)src + n) {
        /* We found no overlap, so let memcpy do all the heavy
         * lifting (prefetching, etc.)
         */
        return memcpy(dest, src, n);
    }

    if (n != 0) {
        const uint8_t *in;
        uint8_t x;
        uint8_t *out;
        int stride;

        if (src < dest) {
            /* copy backwards */
            in = (const uint8_t *)src + n - 1;
            out = (uint8_t *)dest + n - 1;
            stride = -1;
        } else {
            /* copy forwards */
            in = (const uint8_t *)src;
            out = (uint8_t *)dest;
            stride = 1;
        }

        /* Manually software-pipeline this loop. */
        x = *in;
        in += stride;

        while (--n != 0) {
            *out = x;
            out += stride;
            x = *in;
            in += stride;
        }

        *out = x;
    }

    return dest;
}
EXPORT_SYMBOL(memmove);