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83 lines
2.6 KiB
83 lines
2.6 KiB
// |
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// Copyright (C) 2010 The Android Open Source Project |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// http://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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// |
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#include "update_engine/payload_generator/tarjan.h" |
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#include <algorithm> |
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#include <vector> |
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#include <base/logging.h> |
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#include "update_engine/common/utils.h" |
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using std::min; |
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using std::vector; |
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namespace chromeos_update_engine { |
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namespace { |
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const vector<Vertex>::size_type kInvalidIndex = -1; |
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} |
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void TarjanAlgorithm::Execute(Vertex::Index vertex, |
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Graph* graph, |
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vector<Vertex::Index>* out) { |
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stack_.clear(); |
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components_.clear(); |
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index_ = 0; |
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for (Graph::iterator it = graph->begin(); it != graph->end(); ++it) |
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it->index = it->lowlink = kInvalidIndex; |
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required_vertex_ = vertex; |
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Tarjan(vertex, graph); |
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if (!components_.empty()) |
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out->swap(components_[0]); |
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} |
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void TarjanAlgorithm::Tarjan(Vertex::Index vertex, Graph* graph) { |
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CHECK_EQ((*graph)[vertex].index, kInvalidIndex); |
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(*graph)[vertex].index = index_; |
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(*graph)[vertex].lowlink = index_; |
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index_++; |
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stack_.push_back(vertex); |
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for (Vertex::EdgeMap::iterator it = (*graph)[vertex].out_edges.begin(); |
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it != (*graph)[vertex].out_edges.end(); ++it) { |
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Vertex::Index vertex_next = it->first; |
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if ((*graph)[vertex_next].index == kInvalidIndex) { |
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Tarjan(vertex_next, graph); |
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(*graph)[vertex].lowlink = min((*graph)[vertex].lowlink, |
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(*graph)[vertex_next].lowlink); |
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} else if (utils::VectorContainsValue(stack_, vertex_next)) { |
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(*graph)[vertex].lowlink = min((*graph)[vertex].lowlink, |
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(*graph)[vertex_next].index); |
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} |
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} |
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if ((*graph)[vertex].lowlink == (*graph)[vertex].index) { |
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vector<Vertex::Index> component; |
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Vertex::Index other_vertex; |
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do { |
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other_vertex = stack_.back(); |
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stack_.pop_back(); |
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component.push_back(other_vertex); |
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} while (other_vertex != vertex && !stack_.empty()); |
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if (utils::VectorContainsValue(component, required_vertex_)) { |
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components_.resize(components_.size() + 1); |
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component.swap(components_.back()); |
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} |
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} |
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} |
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} // namespace chromeos_update_engine
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