amiga-clib2/library/string_memcmp.c

/*
 * $Id: string_memcmp.c,v 1.1.1.1 2004-07-26 16:32:15 obarthel Exp $
 *
 * :ts=4
 *
 * Portable ISO 'C' (1994) runtime library for the Amiga computer
 * Copyright (c) 2002-2004 by Olaf Barthel <olsen@sourcery.han.de>
 * 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 */

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

#define IS_UNALIGNED(a) 	((((unsigned long)(a)) & 1) != 0)
#define IS_SHORT_ALIGNED(a)	((((unsigned long)(a)) & 3) == 2)
#define IS_LONG_ALIGNED(a)	((((unsigned long)(a)) & 1) == 0)

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

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))
		{
			result = (*m1) - (*m2);
			break;
		}

		m1++;
		m2++;
	}

	return(result);
}

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

int
memcmp(const void *ptr1, const void *ptr2, size_t len)
{
	int result = 0;

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

	#if defined(CHECK_FOR_NULL_POINTERS)
	{
		if(ptr1 == NULL || ptr2 == NULL)
		{
			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))
				{
					result = (*m1) - (*m2);
					break;
				}

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

 out:

	return(result);
}