77 lines
2.9 KiB
C++
77 lines
2.9 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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#include "libtorrent/bloom_filter.hpp"
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#include "libtorrent/aux_/numeric_cast.hpp"
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namespace libtorrent {
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bool has_bits(std::uint8_t const* k, std::uint8_t const* bits, int const len)
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{
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std::uint32_t idx1 = std::uint32_t(k[0]) | (std::uint32_t(k[1]) << 8);
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std::uint32_t idx2 = std::uint32_t(k[2]) | (std::uint32_t(k[3]) << 8);
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idx1 %= aux::numeric_cast<std::uint32_t>(len * 8);
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idx2 %= aux::numeric_cast<std::uint32_t>(len * 8);
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return (bits[idx1 / 8] & (1 << (idx1 & 7))) != 0
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&& (bits[idx2 / 8] & (1 << (idx2 & 7))) != 0;
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}
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void set_bits(std::uint8_t const* k, std::uint8_t* bits, int const len)
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{
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std::uint32_t idx1 = std::uint32_t(k[0]) | (std::uint32_t(k[1]) << 8);
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std::uint32_t idx2 = std::uint32_t(k[2]) | (std::uint32_t(k[3]) << 8);
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idx1 %= aux::numeric_cast<std::uint32_t>(len * 8);
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idx2 %= aux::numeric_cast<std::uint32_t>(len * 8);
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bits[idx1 / 8] |= (1 << (idx1 & 7));
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bits[idx2 / 8] |= (1 << (idx2 & 7));
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}
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int count_zero_bits(std::uint8_t const* bits, int const len)
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{
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// number of bits _not_ set in a nibble
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std::uint8_t bitcount[16] =
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{
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// 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111,
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// 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111
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4, 3, 3, 2, 3, 2, 2, 1,
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3, 2, 2, 1, 2, 1, 1, 0
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};
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int ret = 0;
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for (int i = 0; i < len; ++i)
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{
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ret += bitcount[bits[i] & 0xf];
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ret += bitcount[(bits[i] >> 4) & 0xf];
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}
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return ret;
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}
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}
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