80 lines
2.6 KiB
C++
80 lines
2.6 KiB
C++
/*
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Copyright (c) 2010-2018, Arvid Norberg
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All rights reserved.
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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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* 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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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the distribution.
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* Neither the name of the author nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND 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 COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING 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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#ifndef TORRENT_BLOOM_FILTER_HPP_INCLUDED
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#define TORRENT_BLOOM_FILTER_HPP_INCLUDED
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#include "libtorrent/sha1_hash.hpp"
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#include <cmath> // for log()
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#include <cstdint>
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namespace libtorrent {
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TORRENT_EXTRA_EXPORT void set_bits(std::uint8_t const* b, std::uint8_t* bits, int len);
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TORRENT_EXTRA_EXPORT bool has_bits(std::uint8_t const* b, std::uint8_t const* bits, int len);
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TORRENT_EXTRA_EXPORT int count_zero_bits(std::uint8_t const* bits, int len);
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template <int N>
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struct bloom_filter
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{
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bool find(sha1_hash const& k) const
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{ return has_bits(&k[0], bits, N); }
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void set(sha1_hash const& k)
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{ set_bits(&k[0], bits, N); }
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std::string to_string() const
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{ return std::string(reinterpret_cast<char const*>(&bits[0]), N); }
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void from_string(char const* str)
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{ std::memcpy(bits, str, N); }
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void clear() { std::memset(bits, 0, N); }
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float size() const
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{
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const int c = (std::min)(count_zero_bits(bits, N), (N * 8) - 1);
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const int m = N * 8;
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return std::log(c / float(m)) / (2.f * std::log(1.f - 1.f/m));
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}
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bloom_filter() { clear(); }
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private:
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std::uint8_t bits[N];
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};
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}
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#endif // TORRENT_BLOOM_FILTER_HPP_INCLUDED
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