Add generation counted storage

include/util/binary_heap.hpp

@@ -16,6 +16,40 @@ namespace osrm
 namespace util
 {
 
+template <typename NodeID, typename Key> class GenerationArrayStorage
+{
+    using GenerationCounter = std::uint16_t;
+  public:
+    explicit GenerationArrayStorage(std::size_t size) : positions(size, 0), generation(0), generations(size, 0) {}
+
+    Key &operator[](NodeID node) {
+        generation[node] = generation;
+        return positions[node];
+    }
+
+    Key peek_index(const NodeID node) const {
+        if (generations[node] < generation)
+        {
+            return std::numeric_limits<Key>::max();
+        }
+        return positions[node];
+    }
+
+    void Clear() {
+        generation++;
+        if (generation == std::numeric_limits<GenerationCounter>::max())
+        {
+            std::fill(generations.begin(), generations.end(), 0);
+            std::fill(positions.begin(), positions.end(), 0);
+        }
+    }
+
+  private:
+    GenerationCounter generation;
+    std::vector<GenerationCounter> generations;
+    std::vector<Key> positions;
+};
+
 template <typename NodeID, typename Key> class ArrayStorage
 {
   public: