83 lines
2.6 KiB
C++
83 lines
2.6 KiB
C++
//
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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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