strspn.c   [plain text]

/*-
 * Copyright (c) 2005 David Schultz <das@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: src/lib/libc/string/strspn.c,v 1.5 2005/04/02 18:52:44 das Exp $");

#include <sys/types.h>
#include <limits.h>
#include <string.h>

#define	IDX(c)	((u_char)(c) / LONG_BIT)
#define	BIT(c)	((u_long)1 << ((u_char)(c) % LONG_BIT))

size_t
strspn(const char *s, const char *charset)
{
	/*
	 * NB: idx and bit are temporaries whose use causes gcc 3.4.2 to
	 * generate better code.  Without them, gcc gets a little confused.
	 */
	const char *s1;
	u_long bit;
	u_long tbl[(UCHAR_MAX + 1) / LONG_BIT];
	int idx;

	if(*s == '\0')
		return (0);

#if LONG_BIT == 64	/* always better to unroll on 64-bit architectures */
	tbl[3] = tbl[2] = tbl[1] = tbl[0] = 0;
#else
	for (idx = 0; idx < sizeof(tbl) / sizeof(tbl[0]); idx++)
		tbl[idx] = 0;
#endif
	for (; *charset != '\0'; charset++) {
		idx = IDX(*charset);
		bit = BIT(*charset);
		tbl[idx] |= bit;
	}

	for(s1 = s; ; s1++) {
		idx = IDX(*s1);
		bit = BIT(*s1);
		if ((tbl[idx] & bit) == 0)
			break;
	}
	return (s1 - s);
}