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Add try_emplace_p extension method

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Iterators are invalidated by concurrent insertion (rehash, resize, etc...) whereas for node-based containers, pointers are only invalidated by erase/clear.
This commit is contained in:
Ed Catmur
2023-09-12 00:31:30 +01:00
parent 3362017f22
commit 4468822524
1 changed files with 18 additions and 0 deletions
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parallel_hashmap/phmap.h
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+18
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@@ -4022,6 +4022,24 @@ public:
return std::get<2>(res);
}
// returns {pointer, bool} instead of {iterator, bool} per try_emplace.
// useful for node-based containers, since the pointer is not invalidated by concurrent insert etc.
template <class K = key_type, class... Args>
std::pair<typename parallel_hash_map::parallel_hash_set::pointer, bool> try_emplace_p(K&& k, Args&&... args) {
size_t hashval = this->hash(k);
typename Lockable::UniqueLock m;
auto res = this->find_or_prepare_insert_with_hash(hashval, k, m);
typename Base::Inner *inner = std::get<0>(res);
if (std::get<2>(res)) {
inner->set_.emplace_at(std::get<1>(res), std::piecewise_construct,
std::forward_as_tuple(std::forward<K>(k)),
std::forward_as_tuple(std::forward<Args>(args)...));
inner->set_.set_ctrl(std::get<1>(res), H2(hashval));
}
auto it = this->iterator_at(inner, inner->set_.iterator_at(std::get<1>(res)));
return {&*it, std::get<2>(res)};
}
// ----------- end of phmap extensions --------------------------
template <class K = key_type, class P = Policy, K* = nullptr>