1/*	$NetBSD: wcscspn_bloom.h,v 1.3 2011/11/25 16:46:56 dholland Exp $	*/
2
3/*-
4 * Copyright (c) 2011 Joerg Sonnenberger,
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29/*
30 * Bloom filter for fast test if a given character is part of the reject set.
31 * The test may have false positives, but doesn't have false negatives.
32 * The first hash function is designed to be very fast to evaluate.
33 * It is collision free if the input is part of the same European language
34 * and shouldn't be too bad even other input.  The second hash function
35 * tries to provide a much better mixing, but involves the slower
36 * multiplication.
37 */
38
39#include <limits.h>
40
41#define	BLOOM_SIZE		64
42#define	BLOOM_ARRAY_SIZE	(BLOOM_SIZE / sizeof(size_t))
43#define	BLOOM_BITS		(BLOOM_SIZE * CHAR_BIT)
44#define	BLOOM_DIV		(sizeof(size_t) * CHAR_BIT)
45
46static inline size_t
47wcscspn_bloom1(size_t x)
48{
49	return x % BLOOM_BITS;
50}
51
52static inline size_t
53wcscspn_bloom2(size_t x)
54{
55	return (size_t)((uint32_t)(x * 2654435761U) /
56	    (0x100000000ULL / BLOOM_BITS));
57}
58
59static inline void
60wcsspn_bloom_init(size_t *bloom, const wchar_t *charset)
61{
62	size_t val;
63
64	memset(bloom, 0, BLOOM_SIZE);
65	do {
66		val = wcscspn_bloom1((size_t)*charset);
67		bloom[val / BLOOM_DIV] |= (size_t)1 << (val % BLOOM_DIV);
68		val = wcscspn_bloom2((size_t)*charset);
69		bloom[val / BLOOM_DIV] |= (size_t)1 << (val % BLOOM_DIV);
70	}
71	while (*++charset);
72}
73
74static inline int
75wcsspn_in_bloom(const size_t *bloom, wchar_t ch)
76{
77	size_t val;
78
79	val = wcscspn_bloom1((size_t)ch);
80	if (bloom[val / BLOOM_DIV] & ((size_t)1 << (val % BLOOM_DIV)))
81		return 1;
82	val = wcscspn_bloom2((size_t)ch);
83	if (bloom[val / BLOOM_DIV] & ((size_t)1 << (val % BLOOM_DIV)))
84		return 1;
85	return 0;
86}
87