memchr.c

Go to the documentation of this file.

/*******************************************************************************
 Copyright (c) 2018 Walt Elam
 All rights reserved.
 
 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 of the copyright holder 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 HOLDER 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.
*******************************************************************************/
/***************************************************************************//**
 @file memchr.c
 
 @brief Defines the memchr function
*******************************************************************************/
#include <string.h>
 
/*******************************************************************************
 memchr
*//**
 @brief Searches for a given character
 @param *s Object being searched
 @param c Character to find
 @param n Maximum number of character to search
 
 The memchr function locates the first occurrence of c (converted to an
 unsigned char) in the initial n characters (each interpreted as unsigned
 char) of the object pointed to by s.
 
 @return A pointer to the located character
 @retval NULL The character does not occur in the object
*******************************************************************************/
void *
memchr(const void *s, int c, size_t n)
{
 const unsigned char *pCur = s;
 const unsigned char search = c;
 
 if ( !s ||
 /* Check for wrapping while searching */
 ((((unsigned long) -1) - ((unsigned long) s)) < n))
 {
 return NULL;
 }
 
 while (n-- > 0)
 {
 if (search == *(pCur++))
 {
 return (void *) --pCur;
 }
 }
 
 return NULL;
}