Merge pull request #3864 from obsidiansystems/more-topo-sort

Abstract out topo sorting logic
This commit is contained in:
Eelco Dolstra 2020-08-05 16:07:29 +02:00 committed by GitHub
commit 75f220a595
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2 changed files with 56 additions and 35 deletions

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@ -4,6 +4,7 @@
#include "local-store.hh" #include "local-store.hh"
#include "store-api.hh" #include "store-api.hh"
#include "thread-pool.hh" #include "thread-pool.hh"
#include "topo-sort.hh"
namespace nix { namespace nix {
@ -256,41 +257,21 @@ void Store::queryMissing(const std::vector<StorePathWithOutputs> & targets,
StorePaths Store::topoSortPaths(const StorePathSet & paths) StorePaths Store::topoSortPaths(const StorePathSet & paths)
{ {
StorePaths sorted; return topoSort(paths,
StorePathSet visited, parents; {[&](const StorePath & path) {
std::function<void(const StorePath & path, const StorePath * parent)> dfsVisit;
dfsVisit = [&](const StorePath & path, const StorePath * parent) {
if (parents.count(path))
throw BuildError("cycle detected in the references of '%s' from '%s'",
printStorePath(path), printStorePath(*parent));
if (!visited.insert(path).second) return;
parents.insert(path);
StorePathSet references; StorePathSet references;
try { try {
references = queryPathInfo(path)->references; references = queryPathInfo(path)->references;
} catch (InvalidPath &) { } catch (InvalidPath &) {
} }
return references;
for (auto & i : references) }},
/* Don't traverse into paths that don't exist. That can {[&](const StorePath & path, const StorePath & parent) {
happen due to substitutes for non-existent paths. */ return BuildError(
if (i != path && paths.count(i)) "cycle detected in the references of '%s' from '%s'",
dfsVisit(i, &path); printStorePath(path),
printStorePath(parent));
sorted.push_back(path); }});
parents.erase(path);
};
for (auto & i : paths)
dfsVisit(i, nullptr);
std::reverse(sorted.begin(), sorted.end());
return sorted;
} }

40
src/libutil/topo-sort.hh Normal file
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@ -0,0 +1,40 @@
#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;
}
}