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94 lines
2.3 KiB
C++
94 lines
2.3 KiB
C++
/* Serialization of boost::bloom::filter.
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*
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* Copyright 2025 Joaquin M Lopez Munoz.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See https://www.boost.org/libs/bloom for library home page.
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*/
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#include <boost/bloom/filter.hpp>
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#include <boost/bloom/multiblock.hpp>
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#include <boost/core/detail/splitmix64.hpp>
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#include <boost/cstdint.hpp>
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#include <boost/uuid/uuid.hpp>
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#include <cstring>
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#include <fstream>
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#include <iostream>
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/* emits a deterministic pseudorandom sequence of UUIDs */
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struct uuid_generator
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{
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boost::uuids::uuid operator()()
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{
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boost::uint64_t x = rng();
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std::memcpy(&data[0], &x, sizeof(x));
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x = rng();
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std::memcpy(&data[8], &x, sizeof(x));
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return {data};
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}
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boost::detail::splitmix64 rng;
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std::uint8_t data[16];
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};
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using filter = boost::bloom::filter<
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boost::uuids::uuid, 1, boost::bloom::multiblock<boost::uint64_t, 8> >;
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static constexpr std::size_t num_elements = 10000;
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/* creates a filter with num_elements UUIDs */
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filter create_filter()
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{
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uuid_generator gen;
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filter f(num_elements, 0.005);
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for(std::size_t i = 0; i < num_elements; ++i) f.insert(gen());
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return f;
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}
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static constexpr const char* filename = "filter.bin";
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void save_filter(const filter& f)
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{
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std::ofstream out(filename, std::ios::binary | std::ios::trunc);
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std::size_t c=f.capacity();
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out.write((const char*) &c, sizeof(c)); /* save capacity (bits) */
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auto s = f.array();
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out.write((const char*) s.data(), s.size()); /* save array */
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}
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filter load_filter()
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{
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std::ifstream in(filename, std::ios::binary);
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std::size_t c;
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in.read((char*) &c, sizeof(c));
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filter f(c);
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auto s = f.array();
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in.read((char*) s.data(), s.size()); /* load array */
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return f;
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}
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int main()
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{
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/* creates and saves filter and then loads it */
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save_filter(create_filter());
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auto f = load_filter();
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/* Check that all the UUIDs used on filter creation are actually contained
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* in the restored filter.
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*/
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uuid_generator gen;
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std::size_t n = 0;
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for(std::size_t i = 0; i < num_elements; ++i) {
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if (f.may_contain(gen())) ++n;
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}
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if (n == num_elements) std::cout << "all elements in filter\n";
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else std::cout << "something went wrong\n";
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}
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