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/*
* Copyright (c) 2010-2018 Isode Limited.
* All rights reserved.
* See the COPYING file for more information.
*/
#include <Swiften/Network/DomainNameServiceQuery.h>
#include <cassert>
#include <functional>
#include <iterator>
#include <numeric>
#include <boost/numeric/conversion/cast.hpp>
#include <Swiften/Base/RandomGenerator.h>
using namespace Swift;
namespace {
struct ResultPriorityComparator {
bool operator()(const DomainNameServiceQuery::Result& a, const DomainNameServiceQuery::Result& b) const {
return a.priority < b.priority;
}
};
}
namespace Swift {
DomainNameServiceQuery::~DomainNameServiceQuery() {
}
void DomainNameServiceQuery::sortResults(std::vector<DomainNameServiceQuery::Result>& queries, RandomGenerator& generator) {
ResultPriorityComparator comparator;
std::stable_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), [](const DomainNameServiceQuery::Result& result) {
/* easy hack to account for '0' weights getting at least some weight */
return result.weight + 1;
});
try {
for (int j = 0; j < boost::numeric_cast<int>(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());
auto 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]);
}
}
catch (const boost::numeric::bad_numeric_cast&) {
// In the unlikely event of weights.size() being too large, use the list as-is.
}
}
i = next;
}
}
}
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Swift