mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
77 lines
2.1 KiB
C++
77 lines
2.1 KiB
C++
/*
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This file is part of solidity.
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solidity is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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solidity is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with solidity. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <functional>
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#include <set>
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namespace dev
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{
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/**
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* Detector for cycles in directed graphs. It returns the first
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* vertex on the path towards a cycle or a nullptr if there is
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* no reachable cycle starting from a given vertex.
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*/
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template <typename V>
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class CycleDetector
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{
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public:
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/// Initializes the cycle detector
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/// @param _visit function that is given the current vertex
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/// and is supposed to call @a run on all
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/// adjacent vertices.
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explicit CycleDetector(std::function<void(V const&, CycleDetector&)> _visit):
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m_visit(std::move(_visit))
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{ }
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/// Recursively perform cycle detection starting
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/// (or continuing) with @param _vertex
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/// @returns the first vertex on the path towards a cycle from @a _vertex
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/// or nullptr if no cycle is reachable from @a _vertex.
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V const* run(V const& _vertex)
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{
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if (m_firstCycleVertex)
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return m_firstCycleVertex;
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if (m_processed.count(&_vertex))
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return nullptr;
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else if (m_processing.count(&_vertex))
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return m_firstCycleVertex = &_vertex;
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m_processing.insert(&_vertex);
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m_depth++;
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m_visit(_vertex, *this);
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m_depth--;
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if (m_firstCycleVertex && m_depth == 1)
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m_firstCycleVertex = &_vertex;
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m_processing.erase(&_vertex);
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m_processed.insert(&_vertex);
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return m_firstCycleVertex;
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}
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private:
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std::function<void(V const&, CycleDetector&)> m_visit;
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std::set<V const*> m_processing;
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std::set<V const*> m_processed;
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size_t m_depth = 0;
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V const* m_firstCycleVertex = nullptr;
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};
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}
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