forked from lix-project/lix
42 lines
1 KiB
C++
42 lines
1 KiB
C++
#pragma once
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#include "error.hh"
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namespace nix {
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template<typename T>
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std::vector<T> topoSort(std::set<T> items,
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std::function<std::set<T>(const T &)> getChildren,
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std::function<Error(const T &, const T &)> makeCycleError)
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{
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std::vector<T> sorted;
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std::set<T> visited, parents;
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std::function<void(const T & path, const T * parent)> dfsVisit;
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dfsVisit = [&](const T & path, const T * parent) {
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if (parents.count(path)) throw makeCycleError(path, *parent);
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if (!visited.insert(path).second) return;
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parents.insert(path);
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std::set<T> references = getChildren(path);
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for (auto & i : references)
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/* Don't traverse into items that don't exist in our starting set. */
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if (i != path && items.count(i))
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dfsVisit(i, &path);
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sorted.push_back(path);
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parents.erase(path);
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};
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for (auto & i : items)
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dfsVisit(i, nullptr);
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std::reverse(sorted.begin(), sorted.end());
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return sorted;
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}
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}
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