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/*
* Copyright (c) 2010 Remko Tronçon
* Licensed under the GNU General Public License v3.
* See Documentation/Licenses/GPLv3.txt for more information.
*/
#include <Swiften/Network/DomainNameServiceQuery.h>
#include <numeric>
#include <cassert>
#include <functional>
#include <iterator>
#include <Swiften/Base/RandomGenerator.h>
#include <boost/numeric/conversion/cast.hpp>
using namespace Swift;
namespace {
struct ResultPriorityComparator {
bool operator()(const DomainNameServiceQuery::Result& a, const DomainNameServiceQuery::Result& b) const {
return a.priority < b.priority;
}
};
struct GetWeight {
GetWeight() {}
int operator()(const DomainNameServiceQuery::Result& result) {
return result.weight + 1 /* easy hack to account for '0' weights getting at least some weight */;
}
};
}
namespace Swift {
DomainNameServiceQuery::~DomainNameServiceQuery() {
}
void DomainNameServiceQuery::sortResults(std::vector<DomainNameServiceQuery::Result>& queries, RandomGenerator& generator) {
ResultPriorityComparator comparator;
std::sort(queries.begin(), queries.end(), comparator);
std::vector<DomainNameServiceQuery::Result>::iterator i = queries.begin();
while (i != queries.end()) {
std::vector<DomainNameServiceQuery::Result>::iterator next = std::upper_bound(i, queries.end(), *i, comparator);
if (std::distance(i, next) > 1) {
std::vector<int> weights;
std::transform(i, next, std::back_inserter(weights), GetWeight());
for (size_t j = 0; j < weights.size() - 1; ++j) {
std::vector<int> cumulativeWeights;
std::partial_sum(weights.begin() + j, weights.end(), std::back_inserter(cumulativeWeights));
int randomNumber = generator.generateRandomInteger(cumulativeWeights.back());
int selectedIndex = std::lower_bound(cumulativeWeights.begin(), cumulativeWeights.end(), randomNumber) - cumulativeWeights.begin();
std::swap(i[j], i[j + selectedIndex]);
std::swap(weights.begin()[j], weights.begin()[j + selectedIndex]);
}
}
i = next;
}
}
}
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Swift