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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 <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 WeightAccumulator {
int operator()(int accumulator, const DomainNameServiceQuery::Result& result) {
return accumulator + result.weight;
}
};
struct WeightToProbability {
WeightToProbability(int total) : total(total) {}
double operator()(const DomainNameServiceQuery::Result& result) {
return result.weight / boost::numeric_cast<double>(total);
}
int total;
};
}
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) {
int weightSum = std::accumulate(i, next, 0, WeightAccumulator());
std::vector<double> probabilities;
std::transform(i, next, std::back_inserter(probabilities), WeightToProbability(weightSum > 0 ? weightSum : 1));
// Shuffling the result array and the probabilities in parallel
for (size_t j = 0; j < probabilities.size(); ++j) {
int selectedIndex = generator.generateWeighedRandomNumber(probabilities.begin() + j, probabilities.end());
std::swap(i[j], i[j + selectedIndex]);
std::swap(probabilities.begin()[j], probabilities.begin()[j + selectedIndex]);
}
}
i = next;
}
}
}
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Swift