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1507843f6c
Try to pass by reference where possible. Co-authored-by: Sergei Zimmerman <sergei@zimmerman.foo>
44 lines
1.1 KiB
C++
44 lines
1.1 KiB
C++
#pragma once
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///@file
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#include "nix/util/error.hh"
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namespace nix {
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template<typename T, typename Compare>
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std::vector<T> topoSort(
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std::set<T, Compare> items,
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std::function<std::set<T, Compare>(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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decltype(items) visited, parents;
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auto dfsVisit = [&](this auto & dfsVisit, const T & path, const T * parent) {
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if (parents.count(path))
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throw makeCycleError(path, *parent);
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if (!visited.insert(path).second)
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return;
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parents.insert(path);
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auto 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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} // namespace nix
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