67 lines
1.8 KiB
C
67 lines
1.8 KiB
C
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2022
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#pragma once
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#include "td/utils/common.h"
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#include "td/utils/FlatHashMap.h"
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#include "td/utils/HashTableUtils.h"
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#include <functional>
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namespace td {
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template <class KeyT, class ValueT, class HashT = std::hash<KeyT>, class EqT = std::equal_to<KeyT>>
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class WaitFreeHashMap {
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using Storage = FlatHashMap<KeyT, ValueT, HashT, EqT>;
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static constexpr size_t MAX_STORAGE_COUNT = 256;
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static_assert((MAX_STORAGE_COUNT & (MAX_STORAGE_COUNT - 1)) == 0, "");
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static constexpr size_t MAX_STORAGE_SIZE = MAX_STORAGE_COUNT * MAX_STORAGE_COUNT / 2;
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Storage default_map_;
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struct WaitFreeStorage {
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Storage maps_[MAX_STORAGE_COUNT];
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};
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unique_ptr<WaitFreeStorage> wait_free_storage_;
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Storage &get_storage(const KeyT &key) {
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if (wait_free_storage_ == nullptr) {
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return default_map_;
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}
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return wait_free_storage_->maps_[randomize_hash(HashT()(key)) & (MAX_STORAGE_COUNT - 1)];
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}
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public:
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void set(const KeyT &key, ValueT value) {
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auto &storage = get_storage(key);
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storage[key] = std::move(value);
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if (default_map_.size() == MAX_STORAGE_SIZE) {
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CHECK(wait_free_storage_ == nullptr);
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wait_free_storage_ = make_unique<WaitFreeStorage>();
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for (auto &it : default_map_) {
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get_storage(it.first).emplace(it.first, std::move(it.second));
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}
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default_map_.clear();
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}
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}
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ValueT get(const KeyT &key) {
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auto &storage = get_storage(key);
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auto it = storage.find(key);
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if (it == storage.end()) {
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return {};
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}
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return it->second;
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}
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size_t erase(const KeyT &key) {
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return get_storage(key).erase(key);
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}
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};
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} // namespace td
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