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yangguangcai
108 lines
3.1 KiB
C
108 lines
3.1 KiB
C
/****************************************************************************
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* libs/libc/string/lib_strcat.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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#define ALIGNED(x) \
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(((long)(uintptr_t)(x) & (sizeof(long) - 1)) == 0)
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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_STRCAT) && defined(LIBC_BUILD_STRCAT)
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#undef strcat /* See mm/README.txt */
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nosanitize_address
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FAR char *strcat(FAR char *dest, FAR const char *src)
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{
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#ifdef CONFIG_LIBC_STRING_OPTIMIZE
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FAR char *ret = dest;
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/* Skip over the data in dest as quickly as possible. */
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if (ALIGNED(dest))
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{
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FAR unsigned long *aligned_s1 = (FAR unsigned long *)dest;
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while (!DETECTNULL(*aligned_s1))
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{
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aligned_s1++;
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}
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dest = (FAR char *)aligned_s1;
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}
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while (*dest)
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{
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dest++;
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}
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/* dest now points to the its trailing null character, we can
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* just use strcpy to do the work for us now.
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* ?!? We might want to just include strcpy here.
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* Also, this will cause many more unaligned string copies because
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* dest is much less likely to be aligned. I don't know if its worth
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* tweaking strcpy to handle this better.
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*/
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strcpy(dest, src);
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#else
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FAR char *ret = dest;
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dest += strlen(dest);
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while (*src != '\0')
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{
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*dest++ = *src++;
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}
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*dest = '\0';
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#endif
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return ret;
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}
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#endif
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