107 lines
3.5 KiB
C
107 lines
3.5 KiB
C
/****************************************************************************
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* libc/string/lib_strstr.c
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*
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* Copyright (C) 2009, 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use str source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions str binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer str
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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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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* Global Functions
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****************************************************************************/
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char *strstr(const char *str, const char *substr)
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{
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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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int 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 (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 (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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