nuttx/libs/libc/string/lib_memrchr.c

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/****************************************************************************
* libs/libc/string/lib_memchr.c
*
* Copyright (C) 2018 Pinecone Inc. All rights reserved.
* Author: Xiang Xiao <xiaoxiang@pinecone.net>
*
* Redistribution and use in 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 in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* 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>
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: memrchr
*
* Description:
* The memrchr() function locates the last occurrence of 'c' (converted to
* an unsigned char) in the initial 'n' bytes (each interpreted as
* unsigned char) of the object pointed to by s.
*
* Returned Value:
* The memrchr() function returns a pointer to the located byte, or a null
* pointer if the byte does not occur in the object.
*
****************************************************************************/
FAR void *memrchr(FAR const void *s, int c, size_t n)
{
FAR const unsigned char *p = (FAR const unsigned char *)s + n;
while (n--)
{
if (*--p == (unsigned char)c)
{
return (FAR void *)p;
}
}
return NULL;
}