mem.c

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/*
 * Copyright (c) 2005 Martin Decky
 * Copyright (c) 2008 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 <mem.h>
#include <stdlib.h>
#include <sys/types.h>

void *memset(void *dest, int b, size_t n)
{
        char *pb;
        unsigned long *pw;
        size_t word_size;
        size_t n_words;

        unsigned long pattern;
        size_t i;
        size_t fill;

        /* Fill initial segment. */
        word_size = sizeof(unsigned long);
        fill = word_size - ((uintptr_t) dest & (word_size - 1));
        if (fill > n) fill = n;

        pb = dest;

        i = fill;
        while (i-- != 0)
                *pb++ = b;

        /* Compute remaining size. */
        n -= fill;
        if (n == 0) return dest;

        n_words = n / word_size;
        n = n % word_size;
        pw = (unsigned long *) pb;

        /* Create word-sized pattern for aligned segment. */
        pattern = 0;
        i = word_size;
        while (i-- != 0)
                pattern = (pattern << 8) | (uint8_t) b;

        /* Fill aligned segment. */
        i = n_words;
        while (i-- != 0)
                *pw++ = pattern;

        pb = (char *) pw;

        /* Fill final segment. */
        i = n;
        while (i-- != 0)
                *pb++ = b;

        return dest;
}

struct along {
        unsigned long n;
} __attribute__ ((packed));

static void *unaligned_memcpy(void *dst, const void *src, size_t n)
{
        size_t i, j;
        struct along *adst = dst;
        const struct along *asrc = src;

        for (i = 0; i < n / sizeof(unsigned long); i++)
                adst[i].n = asrc[i].n;
                
        for (j = 0; j < n % sizeof(unsigned long); j++)
                ((unsigned char *) (((unsigned long *) dst) + i))[j] =
                    ((unsigned char *) (((unsigned long *) src) + i))[j];
                
        return (char *) dst;
}

void *memcpy(void *dst, const void *src, size_t n)
{
        size_t i;
        size_t mod, fill;
        size_t word_size;
        size_t n_words;

        const unsigned long *srcw;
        unsigned long *dstw;
        const uint8_t *srcb;
        uint8_t *dstb;

        word_size = sizeof(unsigned long);

        /*
         * Are source and destination addresses congruent modulo word_size?
         * If not, use unaligned_memcpy().
         */

        if (((uintptr_t) dst & (word_size - 1)) !=
            ((uintptr_t) src & (word_size - 1)))
                return unaligned_memcpy(dst, src, n);

        /*
         * mod is the address modulo word size. fill is the length of the
         * initial buffer segment before the first word boundary.
         * If the buffer is very short, use unaligned_memcpy(), too.
         */

        mod = (uintptr_t) dst & (word_size - 1);
        fill = word_size - mod;
        if (fill > n) fill = n;

        /* Copy the initial segment. */

        srcb = src;
        dstb = dst;

        i = fill;
        while (i-- != 0)
                *dstb++ = *srcb++;

        /* Compute remaining length. */

        n -= fill;
        if (n == 0) return dst;

        /* Pointers to aligned segment. */

        dstw = (unsigned long *) dstb;
        srcw = (const unsigned long *) srcb;

        n_words = n / word_size;        /* Number of whole words to copy. */
        n -= n_words * word_size;       /* Remaining bytes at the end. */

        /* "Fast" copy. */
        i = n_words;
        while (i-- != 0)
                *dstw++ = *srcw++;

        /*
         * Copy the rest.
         */

        srcb = (const uint8_t *) srcw;
        dstb = (uint8_t *) dstw;

        i = n;
        while (i-- != 0)
                *dstb++ = *srcb++;

        return dst;
}

void *memmove(void *dst, const void *src, size_t n)
{
        const uint8_t *sp;
        uint8_t *dp;

        /* Nothing to do? */
        if (src == dst)
                return dst;

        /* Non-overlapping? */
        if (dst >= src + n || src >= dst + n) { 
                return memcpy(dst, src, n);
        }

        /* Which direction? */
        if (src > dst) {
                /* Forwards. */
                sp = src;
                dp = dst;

                while (n-- != 0)
                        *dp++ = *sp++;
        } else {
                /* Backwards. */
                sp = src + (n - 1);
                dp = dst + (n - 1);

                while (n-- != 0)
                        *dp-- = *sp--;
        }

        return dst;
}

int bcmp(const void *s1, const void *s2, size_t len)
{
        uint8_t *u1 = (uint8_t *) s1;
        uint8_t *u2 = (uint8_t *) s2;
        
        for (; (len != 0) && (*u1++ == *u2++); len--);
        
        return len;
}

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