mirror of
https://github.com/matrix-construct/construct
synced 2024-07-03 17:28:18 +02:00
109 lines
3.2 KiB
C++
109 lines
3.2 KiB
C++
/*
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* charybdis: 21st Century IRC++d
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*
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* Copyright (C) 2017 Charybdis Development Team
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* Copyright (C) 2017 Jason Volk <jason@zemos.net>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice is present in all copies.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* 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,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#define HAVE_IRCD_CUCKOO_H
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/// Cuckoo filtering and hashing.
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///
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/// This is an API for building cuckoo filters for efficient set membership
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/// tests. Cuckoo filters are a recently celebrated result by Bin Fan inspired
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/// by Mitzenmacher's seminal thesis: the Power Of Two choices in randomized
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/// linear load balancing. These filters are used extensively to optimize
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/// queries made into matrix room state after accumulating events.
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///
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/// Note that the hash residue has to be kept secret from an adversary who
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/// may try to craft strings to attack the filter. A secret salt should be
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/// used. Filters may also be serialized to the db so the salt will have to
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/// persist secretly too.
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///
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namespace ircd::cuckoo
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{
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IRCD_EXCEPTION(ircd::error, error)
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template<class word, size_t words> struct entry;
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template<class entry, size_t entries> struct bucket;
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template<class bucket, size_t buckets> struct table;
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struct filter;
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struct counter;
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}
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template<class word,
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size_t words>
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struct ircd::cuckoo::entry
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:std::array<word, words>
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{
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using array_type = std::array<word, words>;
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};
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template<class entry,
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size_t entries>
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struct ircd::cuckoo::bucket
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:std::array<entry, entries>
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{
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using array_type = std::array<entry, entries>;
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};
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template<class bucket,
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size_t buckets>
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struct ircd::cuckoo::table
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:std::array<bucket, buckets>
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{
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using array_type = std::array<bucket, buckets>;
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static_assert(is_powerof2(buckets), "Bucket count must be power of 2");
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};
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struct ircd::cuckoo::filter
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{
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using entry = cuckoo::entry<uint8_t, 1>;
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using bucket = cuckoo::bucket<entry, 1>;
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using table = cuckoo::table<bucket, 32>;
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table a, b;
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bool has(const string_view &) const;
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void add(const string_view &);
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void del(const string_view &);
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};
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struct ircd::cuckoo::counter
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{
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using int_t = int32_t;
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using entry = cuckoo::entry<int_t, 1>;
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using bucket = cuckoo::bucket<entry, 1>;
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using table = cuckoo::table<bucket, 32>;
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table a, b;
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int_t count(const string_view &) const;
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bool has(const string_view &) const;
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void add(const string_view &);
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void del(const string_view &);
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};
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