tdlight/tdutils/td/utils/WaitFreeHashSet.h

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2022-08-20 15:19:58 +02:00
//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2022
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#pragma once
#include "td/utils/common.h"
#include "td/utils/FlatHashSet.h"
#include "td/utils/HashTableUtils.h"
#include <functional>
namespace td {
template <class KeyT, class HashT = std::hash<KeyT>, class EqT = std::equal_to<KeyT>>
class WaitFreeHashSet {
using Storage = FlatHashSet<KeyT, HashT, EqT>;
static constexpr size_t MAX_STORAGE_COUNT = 1 << 11;
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static_assert((MAX_STORAGE_COUNT & (MAX_STORAGE_COUNT - 1)) == 0, "");
static constexpr size_t MAX_STORAGE_SIZE = 1 << 16;
static_assert((MAX_STORAGE_SIZE & (MAX_STORAGE_SIZE - 1)) == 0, "");
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Storage default_set_;
struct WaitFreeStorage {
Storage sets_[MAX_STORAGE_COUNT];
};
unique_ptr<WaitFreeStorage> wait_free_storage_;
Storage &get_wait_free_storage(const KeyT &key) {
return wait_free_storage_->sets_[randomize_hash(HashT()(key)) & (MAX_STORAGE_COUNT - 1)];
}
Storage &get_storage(const KeyT &key) {
if (wait_free_storage_ == nullptr) {
return default_set_;
}
return get_wait_free_storage(key);
}
const Storage &get_storage(const KeyT &key) const {
return const_cast<WaitFreeHashSet *>(this)->get_storage(key);
}
void split_storage() {
CHECK(wait_free_storage_ == nullptr);
wait_free_storage_ = make_unique<WaitFreeStorage>();
for (auto &it : default_set_) {
get_wait_free_storage(it).insert(it);
}
default_set_.clear();
}
public:
void insert(const KeyT &key) {
auto &storage = get_storage(key);
storage.insert(key);
if (default_set_.size() == MAX_STORAGE_SIZE) {
split_storage();
}
}
size_t count(const KeyT &key) const {
const auto &storage = get_storage(key);
return storage.count(key);
}
size_t erase(const KeyT &key) {
return get_storage(key).erase(key);
}
void foreach(std::function<void(const KeyT &key)> callback) const {
if (wait_free_storage_ == nullptr) {
for (auto &it : default_set_) {
callback(it);
}
return;
}
for (size_t i = 0; i < MAX_STORAGE_COUNT; i++) {
for (auto &it : wait_free_storage_->sets_[i]) {
callback(it);
}
}
}
size_t size() const {
if (wait_free_storage_ == nullptr) {
return default_set_.size();
}
size_t result = 0;
for (size_t i = 0; i < MAX_STORAGE_COUNT; i++) {
result += wait_free_storage_->sets_[i].size();
}
return result;
}
bool empty() const {
if (wait_free_storage_ == nullptr) {
return default_set_.empty();
}
for (size_t i = 0; i < MAX_STORAGE_COUNT; i++) {
if (!wait_free_storage_->sets_[i].empty()) {
return false;
}
}
return true;
}
};
} // namespace td