105 lines
3.1 KiB
C
105 lines
3.1 KiB
C
/****************************************************************************
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* libs/libc/string/lib_bsdmemcmp.c
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*
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* Copyright (c) 1994-2009 Red Hat, Inc. All rights reserved.
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*
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* This copyrighted material is made available to anyone wishing to use,
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* modify, copy, or redistribute it subject to the terms and conditions
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* of the BSD License. This program is distributed in the hope that
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* it will be useful, but WITHOUT ANY WARRANTY expressed or implied,
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* including the implied warranties of MERCHANTABILITY or FITNESS FOR
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* A PARTICULAR PURPOSE. A copy of this license is available at
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* http://www.opensource.org/licenses. Any Red Hat trademarks that are
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* incorporated in the source code or documentation are not subject to
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* the BSD License and may only be used or replicated with the express
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* permission of Red Hat, Inc.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <string.h>
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#include "libc.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* Nonzero if either x or y is not aligned on a "long" boundary. */
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#define UNALIGNED(x, y) \
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(((long)(uintptr_t)(x) & (sizeof(long) - 1)) | ((long)(uintptr_t)(y) & (sizeof(long) - 1)))
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/* How many bytes are copied each iteration of the word copy loop. */
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#define LBLOCKSIZE (sizeof(long))
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/* Threshhold for punting to the byte copier. */
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#define TOO_SMALL(len) ((len) < LBLOCKSIZE)
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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#if !defined(CONFIG_LIBC_ARCH_MEMCMP) && defined(LIBC_BUILD_MEMCMP)
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#undef memcmp /* See mm/README.txt */
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no_builtin("memcmp")
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int memcmp(FAR const void *s1, FAR const void *s2, size_t n)
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{
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FAR unsigned char *p1 = (FAR unsigned char *)s1;
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FAR unsigned char *p2 = (FAR unsigned char *)s2;
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FAR unsigned long *a1;
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FAR unsigned long *a2;
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/* If the size is too small, or either pointer is unaligned,
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* then we punt to the byte compare loop. Hopefully this will
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* not turn up in inner loops.
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*/
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if (!TOO_SMALL(n) && !UNALIGNED(p1, p2))
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{
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/* Otherwise, load and compare the blocks of memory one
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* word at a time.
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*/
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a1 = (FAR unsigned long *)p1;
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a2 = (FAR unsigned long *)p2;
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while (n >= LBLOCKSIZE)
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{
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if (*a1 != *a2)
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{
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break;
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}
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a1++;
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a2++;
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n -= LBLOCKSIZE;
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}
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/* check s mod LBLOCKSIZE remaining characters */
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p1 = (FAR unsigned char *)a1;
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p2 = (FAR unsigned char *)a2;
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}
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while (n--)
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{
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if (*p1 != *p2)
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{
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return *p1 - *p2;
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}
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p1++;
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p2++;
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}
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return 0;
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}
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#endif
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