def007e2d7
since it's useful to redirect these functions to others sometime(e.g. validate the memory before write). Change-Id: I6253a9231af8809e8362f4bc5a1bd67fb094c3b0
92 lines
2.8 KiB
C
92 lines
2.8 KiB
C
/****************************************************************************
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* libs/libc/string/lib_strstr.c
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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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/****************************************************************************
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* Public Functions
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****************************************************************************/
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#undef strstr /* See mm/README.txt */
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FAR char *strstr(FAR const char *str, FAR const char *substr)
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{
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FAR const char *candidate; /* Candidate in str with matching start character */
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char ch; /* First character of the substring */
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size_t len; /* The length of the substring */
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/* Special case the empty substring */
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len = strlen(substr);
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ch = *substr;
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if (!ch)
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{
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/* We'll say that an empty substring matches at the beginning of
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* the string
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*/
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return (FAR char *)str;
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}
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/* Search for the substring */
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candidate = str;
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for (; ; )
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{
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/* strchr() will return a pointer to the next occurrence of the
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* character ch in the string
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*/
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candidate = strchr(candidate, ch);
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if (!candidate || strlen(candidate) < len)
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{
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/* First character of the substring does not appear in the string
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* or the remainder of the string is not long enough to contain the
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* substring.
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*/
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return NULL;
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}
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/* Check if this is the beginning of a matching substring */
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if (strncmp(candidate, substr, len) == 0)
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{
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return (FAR char *)candidate;
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}
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/* No, find the next candidate after this one */
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candidate++;
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}
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/* Won't get here, but some compilers might complain. Other compilers
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* might complain about this code being unreachable too.
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*/
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return NULL;
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}
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