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/*-
* Copyright (c) 2012 Ed Schouten <ed@FreeBSD.org>
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/libkern.h>
#include <sys/limits.h>
#include <sys/param.h>
/*
* memcchr(): find first character in buffer not matching `c'.
*
* This function performs the complement of memchr(). To provide decent
* performance, this function compares data from the buffer one word at
* a time.
*
* This code is inspired by libc's strlen(), written by Xin Li.
*/
#if LONG_BIT != 32 && LONG_BIT != 64
#error Unsupported word size
#endif
#define LONGPTR_MASK (sizeof(long) - 1)
#define TESTBYTE \
do { \
if (*p != (unsigned char)c) \
goto done; \
p++; \
} while (0)
void *
memcchr(const void *begin, int c, size_t n)
{
const unsigned long *lp;
const unsigned char *p, *end;
unsigned long word;
/* Four or eight repetitions of `c'. */
word = (unsigned char)c;
word |= word << 8;
word |= word << 16;
#if LONG_BIT >= 64
word |= word << 32;
#endif
/* Don't perform memory I/O when passing a zero-length buffer. */
if (n == 0)
return (NULL);
/*
* First determine whether there is a character unequal to `c'
* in the first word. As this word may contain bytes before
* `begin', we may execute this loop spuriously.
*/
lp = (const unsigned long *)((uintptr_t)begin & ~LONGPTR_MASK);
end = (const unsigned char *)begin + n;
if (*lp++ != word)
for (p = begin; p < (const unsigned char *)lp;)
TESTBYTE;
/* Now compare the data one word at a time. */
for (; (const unsigned char *)lp < end; lp++) {
if (*lp != word) {
p = (const unsigned char *)lp;
TESTBYTE;
TESTBYTE;
TESTBYTE;
#if LONG_BIT >= 64
TESTBYTE;
TESTBYTE;
TESTBYTE;
TESTBYTE;
#endif
goto done;
}
}
return (NULL);
done:
/*
* If the end of the buffer is not word aligned, the previous
* loops may obtain an address that's beyond the end of the
* buffer.
*/
if (p < end)
return (__DECONST(void *, p));
return (NULL);
}
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