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100 lines
3.2 KiB
C
100 lines
3.2 KiB
C
/****************************************************************************
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* libs/libc/string/lib_strstr.c
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2014-2015 Tal Einat
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation files
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* (the "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to permit
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* persons to whom the Software is furnished to do so, subject to the
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* following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE
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* SOFTWARE.
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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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