strchrnul.c

/*-
 * SPDX-License-Identifier: MIT
 *
 * Copyright (c) 2005-2014 Rich Felker, et al.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
#include <limits.h>
#include <stdint.h>
#include <string.h>

#define ALIGN (sizeof(size_t))
#define ONES ((size_t)-1 / UCHAR_MAX)
#define HIGHS (ONES * (UCHAR_MAX / 2 + 1))
#define HASZERO(x) (((x)-ONES) & ~(x)&HIGHS)

char *__strchrnul(const char *, int);

char *
__strchrnul(const char *s, int c)
{
	c = (unsigned char)c;
	if (!c)
		return (char *)s + strlen(s);

#ifdef __GNUC__
	typedef size_t __attribute__((__may_alias__)) word;
	const word *w;
	for (; (uintptr_t)s % ALIGN; s++)
		if (!*s || *(unsigned char *)s == c)
			return (char *)s;
	size_t k = ONES * c;
	for (w = (void *)s; !HASZERO(*w) && !HASZERO(*w ^ k); w++)
		;
	s = (void *)w;
#endif
	for (; *s && *(unsigned char *)s != c; s++)
		;
	return (char *)s;
}

__weak_reference(__strchrnul, strchrnul);