119 lines
3.4 KiB
C
119 lines
3.4 KiB
C
/****************************************************************************
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* libs/libc/string/lib_strcmp.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 <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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/* Macros for detecting endchar */
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#if LONG_MAX == 2147483647
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# define DETECTNULL(x) (((x) - 0x01010101) & ~(x) & 0x80808080)
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#elif LONG_MAX == 9223372036854775807
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/* Nonzero if x (a long int) contains a NULL byte. */
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# define DETECTNULL(x) (((x) - 0x0101010101010101) & ~(x) & 0x8080808080808080)
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#endif
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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_STRCMP) && defined(LIBC_BUILD_STRCMP)
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#undef strcmp /* See mm/README.txt */
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int strcmp(FAR const char *cs, FAR const char *ct)
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{
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#ifdef CONFIG_LIBC_STRING_OPTIMIZE
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FAR unsigned long *a1;
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FAR unsigned long *a2;
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/* If cs or ct are unaligned, then compare bytes. */
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if (!UNALIGNED(cs, ct))
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{
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/* If cs and ct are word-aligned, compare them a word at a time. */
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a1 = (FAR unsigned long *)cs;
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a2 = (FAR unsigned long *)ct;
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while (*a1 == *a2)
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{
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/* To get here, *a1 == *a2, thus if we find a null in *a1,
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* then the strings must be equal, so return zero.
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*/
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if (DETECTNULL(*a1))
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{
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return 0;
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}
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a1++;
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a2++;
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}
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/* A difference was detected in last few bytes of cs,
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* so search bytewise.
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*/
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cs = (FAR char *)a1;
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ct = (FAR char *)a2;
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}
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while (*cs != '\0' && *cs == *ct)
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{
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cs++;
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ct++;
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}
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return (*(FAR unsigned char *)cs) - (*(FAR unsigned char *)ct);
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#else
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register int result;
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for (; ; )
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{
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if ((result = (unsigned char)*cs - (unsigned char)*ct++) != 0 ||
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*cs++ == '\0')
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{
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break;
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}
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}
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return result;
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#endif
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}
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#endif
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