87 lines
2.9 KiB
C
87 lines
2.9 KiB
C
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/* $NetBSD: wcscspn_bloom.h,v 1.4 2011/11/25 17:48:22 joerg Exp $ */
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/*-
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* Copyright (c) 2011 Joerg Sonnenberger,
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* Bloom filter for fast test if a given character is part of the reject set.
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* The test may have false positives, but doesn't have false negatives.
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* The first hash function is designed to be very fast to evaluate.
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* It is collision free if the input is part of the same European language
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* and shouldn't be too bad even other input. The second hash function
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* tries to provide a much better mixing, but involves the slower
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* multiplication.
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*/
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#include <limits.h>
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#define BLOOM_SIZE 64
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#define BLOOM_ARRAY_SIZE (BLOOM_SIZE / sizeof(size_t))
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#define BLOOM_BITS (BLOOM_SIZE * CHAR_BIT)
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#define BLOOM_DIV (sizeof(size_t) * CHAR_BIT)
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static inline size_t
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wcscspn_bloom1(size_t x)
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{
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return x % BLOOM_BITS;
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}
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static inline size_t
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wcscspn_bloom2(size_t x)
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{
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return (size_t)((uint32_t)(x * 2654435761U) /
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(0x100000000ULL / BLOOM_BITS));
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}
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static inline void
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wcsspn_bloom_init(size_t *bloom, const wchar_t *charset)
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{
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size_t val;
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memset(bloom, 0, BLOOM_SIZE);
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do {
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val = wcscspn_bloom1((size_t)*charset);
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bloom[val / BLOOM_DIV] |= (size_t)1 << (val % BLOOM_DIV);
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val = wcscspn_bloom2((size_t)*charset);
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bloom[val / BLOOM_DIV] |= (size_t)1 << (val % BLOOM_DIV);
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}
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while (*++charset);
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}
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static inline int
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wcsspn_in_bloom(const size_t *bloom, wchar_t ch)
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{
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size_t val;
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val = wcscspn_bloom1((size_t)ch);
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if (bloom[val / BLOOM_DIV] & ((size_t)1 << (val % BLOOM_DIV)))
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return 1;
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val = wcscspn_bloom2((size_t)ch);
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if (bloom[val / BLOOM_DIV] & ((size_t)1 << (val % BLOOM_DIV)))
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return 1;
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return 0;
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}
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