strcspn.c revision 331722 
1/*-
2 * Copyright (c) 2005 David Schultz <das@FreeBSD.ORG>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: stable/11/lib/libc/string/strcspn.c 331722 2018-03-29 02:50:57Z eadler $");
29
30#include <sys/types.h>
31#include <limits.h>
32#include <string.h>
33
34#define	IDX(c)	((u_char)(c) / LONG_BIT)
35#define	BIT(c)	((u_long)1 << ((u_char)(c) % LONG_BIT))
36
37size_t
38strcspn(const char *s, const char *charset)
39{
40	/*
41	 * NB: idx and bit are temporaries whose use causes gcc 3.4.2 to
42	 * generate better code.  Without them, gcc gets a little confused.
43	 */
44	const char *s1;
45	u_long bit;
46	u_long tbl[(UCHAR_MAX + 1) / LONG_BIT];
47	int idx;
48
49	if(*s == '\0')
50		return (0);
51
52#if LONG_BIT == 64	/* always better to unroll on 64-bit architectures */
53	tbl[0] = 1;
54	tbl[3] = tbl[2] = tbl[1] = 0;
55#else
56	for (tbl[0] = idx = 1; idx < sizeof(tbl) / sizeof(tbl[0]); idx++)
57		tbl[idx] = 0;
58#endif
59	for (; *charset != '\0'; charset++) {
60		idx = IDX(*charset);
61		bit = BIT(*charset);
62		tbl[idx] |= bit;
63	}
64
65	for(s1 = s; ; s1++) {
66		idx = IDX(*s1);
67		bit = BIT(*s1);
68		if ((tbl[idx] & bit) != 0)
69			break;
70	}
71	return (s1 - s);
72}
73