98 lines
3.0 KiB
C++
98 lines
3.0 KiB
C++
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/*
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Copyright (c) 2006, 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 <algorithm>
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#include <iomanip>
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#include <cassert>
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#include <boost/bind.hpp>
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#include "libtorrent/kademlia/node_id.hpp"
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using boost::bind;
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namespace libtorrent { namespace dht
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{
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// returns the distance between the two nodes
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// using the kademlia XOR-metric
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node_id distance(node_id const& n1, node_id const& n2)
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{
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node_id ret;
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node_id::iterator k = ret.begin();
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for (node_id::const_iterator i = n1.begin(), j = n2.begin()
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, end(n1.end()); i != end; ++i, ++j, ++k)
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{
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*k = *i ^ *j;
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}
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return ret;
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}
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// returns true if: distance(n1, ref) < distance(n2, ref)
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bool compare_ref(node_id const& n1, node_id const& n2, node_id const& ref)
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{
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for (node_id::const_iterator i = n1.begin(), j = n2.begin()
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, k = ref.begin(), end(n1.end()); i != end; ++i, ++j, ++k)
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{
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boost::uint8_t lhs = (*i ^ *k);
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boost::uint8_t rhs = (*j ^ *k);
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if (lhs < rhs) return true;
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if (lhs > rhs) return false;
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}
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return false;
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}
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// returns n in: 2^n <= distance(n1, n2) < 2^(n+1)
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// useful for finding out which bucket a node belongs to
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int distance_exp(node_id const& n1, node_id const& n2)
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{
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int byte = node_id::size - 1;
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for (node_id::const_iterator i = n1.begin(), j = n2.begin()
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, end(n1.end()); i != end; ++i, ++j, --byte)
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{
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assert(byte >= 0);
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boost::uint8_t t = *i ^ *j;
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if (t == 0) continue;
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// we have found the first non-zero byte
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// return the bit-number of the first bit
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// that differs
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int bit = byte * 8;
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for (int b = 7; b > 0; --b)
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if (t >= (1 << b)) return bit + b;
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return bit;
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}
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return 0;
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}
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} } // namespace libtorrent::dht
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