1 files changed, 55 insertions, 0 deletions
diff --git a/Swiften/Network/DomainNameServiceQuery.cpp b/Swiften/Network/DomainNameServiceQuery.cpp
index 5713b63..eb999e0 100644
--- a/Swiften/Network/DomainNameServiceQuery.cpp
+++ b/Swiften/Network/DomainNameServiceQuery.cpp
@@ -6,9 +6,64 @@
 
 #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));
+
+			// 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;
+	}
+}
+
+
 }