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/****************************************************************************
* lib/string/lib_strstr.c
*
* Copyright (C) 2009, 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use str source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions str binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer str
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <string.h>
/****************************************************************************
* Global Functions
****************************************************************************/
char *strstr(const char *str, const char *substr)
{
const char *candidate; /* Candidate in str with matching start character */
char ch; /* First character of the substring */
int len; /* The length of the substring */
/* Special case the empty substring */
len = strlen(substr);
ch = *substr;
if (!ch)
{
/* We'll say that an empty substring matches at the beginning of
* the string
*/
return (char*)str;
}
/* Search for the substring */
candidate = str;
for (;;)
{
/* strchr() will return a pointer to the next occurrence of the
* character ch in the string
*/
candidate = strchr(candidate, ch);
if (!candidate || strlen(candidate) < len)
{
/* First character of the substring does not appear in the string
* or the remainder of the string is not long enough to contain the
* substring.
*/
return NULL;
}
/* Check if this is the beginning of a matching substring */
if (strncmp(candidate, substr, len) == 0)
{
return (char*)candidate;
}
/* No, find the next candidate after this one */
candidate++;
}
/* Won't get here, but some compilers might complain */
return NULL;
}
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