70 lines
1.7 KiB
C++
70 lines
1.7 KiB
C++
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#include <set>
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#include <future>
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#include "sync.hh"
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using std::set;
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namespace nix {
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template<typename T>
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using GetEdgesAsync = std::function<void(const T &, std::function<void(std::promise<set<T>> &)>)>;
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template<typename T>
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void computeClosure(
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const set<T> startElts,
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set<T> & res,
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GetEdgesAsync<T> getEdgesAsync
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)
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{
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struct State
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{
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size_t pending;
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set<T> & res;
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std::exception_ptr exc;
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};
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Sync<State> state_(State{0, res, 0});
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std::function<void(const T &)> enqueue;
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std::condition_variable done;
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enqueue = [&](const T & current) -> void {
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{
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auto state(state_.lock());
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if (state->exc) return;
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if (!state->res.insert(current).second) return;
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state->pending++;
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}
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getEdgesAsync(current, [&](std::promise<set<T>> & prom) {
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try {
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auto children = prom.get_future().get();
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for (auto & child : children)
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enqueue(child);
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{
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auto state(state_.lock());
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assert(state->pending);
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if (!--state->pending) done.notify_one();
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}
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} catch (...) {
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auto state(state_.lock());
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if (!state->exc) state->exc = std::current_exception();
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assert(state->pending);
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if (!--state->pending) done.notify_one();
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};
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});
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};
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for (auto & startElt : startElts)
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enqueue(startElt);
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{
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auto state(state_.lock());
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while (state->pending) state.wait(done);
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if (state->exc) std::rethrow_exception(state->exc);
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}
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}
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}
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