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- /*-
- * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
- *
- * 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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