closure.hh

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#pragma once
 
#include "lix/libutil/async.hh"
#include "lix/libutil/result.hh"
#include <functional>
#include <kj/async.h>
#include <set>
 
namespace nix {
 
template<typename T>
std::set<T> computeClosure(
    std::set<T> startElts,
    std::function<std::set<T>(const T &)> getEdges
)
{
    std::set<T> res, queue = std::move(startElts);
 
    while (!queue.empty()) {
        std::set<T> next;
 
        for (auto & e : queue) {
            if (res.insert(e).second) {
                next.merge(getEdges(e));
            }
        }
 
        queue = std::move(next);
    }
 
    return res;
}
 
template<typename T>
kj::Promise<Result<std::set<T>>> computeClosureAsync(
    std::set<T> startElts,
    std::function<kj::Promise<Result<std::set<T>>>(const T &)> getEdges
)
try {
    std::set<T> res, queue = std::move(startElts);
 
    while (!queue.empty()) {
        std::set<T> next;
 
        for (auto & e : queue) {
            if (res.insert(e).second) {
                next.merge(LIX_TRY_AWAIT(getEdges(e)));
            }
        }
 
        queue = std::move(next);
    }
 
    co_return res;
} catch (...) {
    co_return result::current_exception();
}
 
}