tarjan.h revision f9cb98c0cacccca803db48502c7bd461d04cb6b0 
1// Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef UPDATE_ENGINE_PAYLOAD_GENERATOR_TARJAN_H_
6#define UPDATE_ENGINE_PAYLOAD_GENERATOR_TARJAN_H_
7
8// This is an implementation of Tarjan's algorithm which finds all
9// Strongly Connected Components in a graph.
10
11// Note: a true Tarjan algorithm would find all strongly connected components
12// in the graph. This implementation will only find the strongly connected
13// component containing the vertex passed in.
14
15#include <vector>
16
17#include "update_engine/payload_generator/graph_types.h"
18
19namespace chromeos_update_engine {
20
21class TarjanAlgorithm {
22 public:
23  TarjanAlgorithm() : index_(0), required_vertex_(0) {}
24
25  // 'out' is set to the result if there is one, otherwise it's untouched.
26  void Execute(Vertex::Index vertex,
27               Graph* graph,
28               std::vector<Vertex::Index>* out);
29 private:
30  void Tarjan(Vertex::Index vertex, Graph* graph);
31
32  Vertex::Index index_;
33  Vertex::Index required_vertex_;
34  std::vector<Vertex::Index> stack_;
35  std::vector<std::vector<Vertex::Index>> components_;
36};
37
38}  // namespace chromeos_update_engine
39
40#endif  // UPDATE_ENGINE_PAYLOAD_GENERATOR_TARJAN_H_
41