132 lines
3.5 KiB
C
132 lines
3.5 KiB
C
/****************************************************************************
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* libs/libc/string/lib_memcmp.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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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#ifdef CONFIG_LIBC_STRING_OPTIMIZE
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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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#endif
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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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#ifdef CONFIG_LIBC_STRING_OPTIMIZE
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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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#else
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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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while (n-- > 0)
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{
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if (*p1 < *p2)
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{
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return -1;
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}
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else if (*p1 > *p2)
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{
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return 1;
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}
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p1++;
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p2++;
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}
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#endif
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return 0;
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}
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#endif
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