src/kademlia/node_id.cpp

   1 /*
   2
   3 Copyright (c) 2006, Arvid Norberg
   4 All rights reserved.
   5
   6 Redistribution and use in source and binary forms, with or without
   7 modification, are permitted provided that the following conditions
   8 are met:
   9
  10     * Redistributions of source code must retain the above copyright
  11       notice, this list of conditions and the following disclaimer.
  12     * Redistributions in binary form must reproduce the above copyright
  13       notice, this list of conditions and the following disclaimer in
  14       the documentation and/or other materials provided with the distribution.
  15     * Neither the name of the author nor the names of its
  16       contributors may be used to endorse or promote products derived
  17       from this software without specific prior written permission.
  18
  19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  20 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  23 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29 POSSIBILITY OF SUCH DAMAGE.
  30
  31 */
  32
  33 #include "libtorrent/pch.hpp"
  34
  35 #include <algorithm>
  36 #include <iomanip>
  37 #include <ctime>
  38 #include <boost/bind.hpp>
  39
  40 #include "libtorrent/kademlia/node_id.hpp"
  41 #include "libtorrent/hasher.hpp"
  42 #include "libtorrent/assert.hpp"
  43
  44 using boost::bind;
  45
  46 namespace libtorrent { namespace dht
  47 {
  48
  49 // returns the distance between the two nodes
  50 // using the kademlia XOR-metric
  51 node_id distance(node_id const& n1, node_id const& n2)
  52 {
  53         node_id ret;
  54         node_id::iterator k = ret.begin();
  55         for (node_id::const_iterator i = n1.begin(), j = n2.begin()
  56                 , end(n1.end()); i != end; ++i, ++j, ++k)
  57         {
  58                 *k = *i ^ *j;
  59         }
  60         return ret;
  61 }
  62
  63 // returns true if: distance(n1, ref) < distance(n2, ref)
  64 bool compare_ref(node_id const& n1, node_id const& n2, node_id const& ref)
  65 {
  66         for (node_id::const_iterator i = n1.begin(), j = n2.begin()
  67                 , k = ref.begin(), end(n1.end()); i != end; ++i, ++j, ++k)
  68         {
  69                 boost::uint8_t lhs = (*i ^ *k);
  70                 boost::uint8_t rhs = (*j ^ *k);
  71                 if (lhs < rhs) return true;
  72                 if (lhs > rhs) return false;
  73         }
  74         return false;
  75 }
  76
  77 // returns n in: 2^n <= distance(n1, n2) < 2^(n+1)
  78 // useful for finding out which bucket a node belongs to
  79 int distance_exp(node_id const& n1, node_id const& n2)
  80 {
  81         int byte = node_id::size - 1;
  82         for (node_id::const_iterator i = n1.begin(), j = n2.begin()
  83                 , end(n1.end()); i != end; ++i, ++j, --byte)
  84         {
  85                 TORRENT_ASSERT(byte >= 0);
  86                 boost::uint8_t t = *i ^ *j;
  87                 if (t == 0) continue;
  88                 // we have found the first non-zero byte
  89                 // return the bit-number of the first bit
  90                 // that differs
  91                 int bit = byte * 8;
  92                 for (int b = 7; b >= 0; --b)
  93                         if (t >= (1 << b)) return bit + b;
  94                 return bit;
  95         }
  96
  97         return 0;
  98 }
  99
 100 struct static_ { static_() { std::srand(std::time(0)); } } static__;
 101
 102 node_id generate_id()
 103 {
 104         char random[20];
 105 #ifdef _MSC_VER
 106         std::generate(random, random + 20, &rand);
 107 #else
 108         std::generate(random, random + 20, &std::rand);
 109 #endif
 110
 111         hasher h;
 112         h.update(random, 20);
 113         return h.final();
 114 }
 115
 116 } }  // namespace libtorrent::dht
 117