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