upload android base code part6

android/system/update_engine/payload_generator/tarjan.h

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+//
+// Copyright (C) 2010 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_PAYLOAD_GENERATOR_TARJAN_H_
+#define UPDATE_ENGINE_PAYLOAD_GENERATOR_TARJAN_H_
+
+// This is an implementation of Tarjan's algorithm which finds all
+// Strongly Connected Components in a graph.
+
+// Note: a true Tarjan algorithm would find all strongly connected components
+// in the graph. This implementation will only find the strongly connected
+// component containing the vertex passed in.
+
+#include <vector>
+
+#include "update_engine/payload_generator/graph_types.h"
+
+namespace chromeos_update_engine {
+
+class TarjanAlgorithm {
+ public:
+  TarjanAlgorithm() : index_(0), required_vertex_(0) {}
+
+  // 'out' is set to the result if there is one, otherwise it's untouched.
+  void Execute(Vertex::Index vertex,
+               Graph* graph,
+               std::vector<Vertex::Index>* out);
+ private:
+  void Tarjan(Vertex::Index vertex, Graph* graph);
+
+  Vertex::Index index_;
+  Vertex::Index required_vertex_;
+  std::vector<Vertex::Index> stack_;
+  std::vector<std::vector<Vertex::Index>> components_;
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // UPDATE_ENGINE_PAYLOAD_GENERATOR_TARJAN_H_