adtools/clib2

/*
 * $Id: string_memcmp.c,v 1.8 2010-08-20 15:33:36 obarthel Exp $
 *
 * :ts=4
 *
 * Portable ISO 'C' (1994) runtime library for the Amiga computer
 * Copyright (c) 2002-2015 by Olaf Barthel <obarthel (at) gmx.net>
 * 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.
 *
 *   - Neither the name of Olaf Barthel nor the names of contributors
 *     may be used to endorse or promote products derived from this
 *     software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
 */

#ifndef _STDLIB_NULL_POINTER_CHECK_H
#include "stdlib_null_pointer_check.h"
#endif /* _STDLIB_NULL_POINTER_CHECK_H */

/****************************************************************************/

#ifndef _STRING_HEADERS_H
#include "string_headers.h"
#endif /* _STRING_HEADERS_H */

/****************************************************************************/

INLINE STATIC int
__memcmp(const char *m1,const char *m2,size_t len)
{
    int result = 0;

    assert( m1 != NULL && m2 != NULL && len > 0 );

    /* The setup below is intended to speed up searching in larger
     * memory blocks. This can be very elaborate and should not be
     * done unless a payoff can be expected.
     */
    if(len > 4 * sizeof(long))
    {
        /* Try to align both memory blocks to even addresses. */
        if(IS_UNALIGNED(m1) && IS_UNALIGNED(m2))
        {
            len--;

            if((*m1) != (*m2))
            {
                result = (*m1) - (*m2);
                goto out;
            }

            m1++;
            m2++;
        }

        /* Try to align both memory blocks to addresses which are a
         * long word multiple.
         */
        if(len >= sizeof(short) && IS_SHORT_ALIGNED(m1) && IS_SHORT_ALIGNED(m2))
        {
            const short * _m1 = (const short *)m1;
            const short * _m2 = (const short *)m2;

            /* Check if the two words are different, and if they are,
             * figure out down below which of the bytes were different.
             */
            if((*_m1++) != (*_m2++))
                goto out;

            m1 = (const char *)_m1;
            m2 = (const char *)_m2;

            len -= sizeof(short);
        }

        /* If both memory blocks are aligned to addresses which can be
         * read directly one long word at a time, perform the comparison
         * in that manner.
         */
        if(len >= sizeof(long) && IS_LONG_ALIGNED(m1) && IS_LONG_ALIGNED(m2))
        {
            const long * _m1 = (const long *)m1;
            const long * _m2 = (const long *)m2;

            do
            {
                /* If the two long words are different, figure out down
                 * below which of the bytes were different.
                 */
                if((*_m1) != (*_m2))
                {
                    m1 = (const char *)_m1;
                    m2 = (const char *)_m2;

                    goto out;
                }

                _m1++;
                _m2++;

                len -= sizeof(long);
            }
            while(len >= sizeof(long));

            m1 = (const char *)_m1;
            m2 = (const char *)_m2;
        }
    }

 out:

    /* If there are bytes left in need of comparison, take
     * care of them here. This also includes 'aborted'
     * comparison attempts from above.
     */
    while(len-- > 0)
    {
        if((*m1) != (*m2))
        {
            int b1,b2;
            
            /* The comparison must be performed as if the
               bytes were unsigned characters. */
            b1 = *(unsigned char *)m1;
            b2 = *(unsigned char *)m2;

            result = b1 - b2;
            break;
        }

        m1++;
        m2++;
    }

    return(result);
}

/****************************************************************************/

/* This is ugly: GCC 2.95.x assumes that 'unsigned long' is used in the built-in
   memcmp/memcpy/memset functions instead of 'size_t'. This can produce warnings
   where none are necessary. */
#if defined(__GNUC__) && (__GNUC__ < 3)
int
memcmp(const void *ptr1, const void *ptr2, unsigned long len)
#else
int
memcmp(const void *ptr1, const void *ptr2, size_t len)
#endif /* __GNUC__ && __GNUC__ < 3 */
{
    int result = 0;

    assert( ptr1 != NULL && ptr2 != NULL );
    assert( (int)len >= 0 );

    #if defined(CHECK_FOR_NULL_POINTERS)
    {
        if(ptr1 == NULL || ptr2 == NULL)
        {
            __set_errno(EFAULT);
            goto out;
        }
    }
    #endif /* CHECK_FOR_NULL_POINTERS */

    if(ptr1 != ptr2 && len > 0)
    {
        const char * m1 = ptr1;
        const char * m2 = ptr2;

        #if 0
        {
            do
            {
                if((*m1) != (*m2))
                {
                    int b1,b2;

                    b1 = *(unsigned char *)m1;
                    b2 = *(unsigned char *)m2;

                    result = b1 - b2;
                    break;
                }

                m1++;
                m2++;
            }
            while(--len > 0);
        }
        #else
        {
            result = __memcmp(m1,m2,len);
        }
        #endif
    }

 out:

    return(result);
}