tdlight/tdutils/td/utils/FlatHashTable.h

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//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2023
//
// 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/HashTableUtils.h"
#include <cstddef>
#include <initializer_list>
#include <iterator>
#include <utility>
namespace td {
namespace detail {
uint32 normalize_flat_hash_table_size(uint32 size);
uint32 get_random_flat_hash_table_bucket(uint32 bucket_count_mask);
} // namespace detail
template <class NodeT, class HashT, class EqT>
class FlatHashTable {
static constexpr uint32 INVALID_BUCKET = 0xFFFFFFFF;
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void allocate_nodes(uint32 size) {
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DCHECK(size >= 8);
DCHECK((size & (size - 1)) == 0);
CHECK(size <= min(static_cast<uint32>(1) << 29, static_cast<uint32>(0x7FFFFFFF / sizeof(NodeT))));
nodes_ = new NodeT[size];
// used_node_count_ = 0;
bucket_count_mask_ = size - 1;
bucket_count_ = size;
begin_bucket_ = INVALID_BUCKET;
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}
static void clear_nodes(NodeT *nodes) {
delete[] nodes;
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}
public:
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using KeyT = typename NodeT::public_key_type;
using key_type = typename NodeT::public_key_type;
using value_type = typename NodeT::public_type;
// TODO use EndSentinel for end() after switching to C++17
// struct EndSentinel {};
struct Iterator {
using iterator_category = std::forward_iterator_tag;
using difference_type = std::ptrdiff_t;
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using value_type = FlatHashTable::value_type;
using pointer = value_type *;
using reference = value_type &;
Iterator &operator++() {
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DCHECK(it_ != nullptr);
do {
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if (unlikely(++it_ == end_)) {
it_ = begin_;
}
if (unlikely(it_ == start_)) {
it_ = nullptr;
break;
}
} while (it_->empty());
return *this;
}
reference operator*() {
return it_->get_public();
}
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const value_type &operator*() const {
return it_->get_public();
}
pointer operator->() {
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return &it_->get_public();
}
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const value_type *operator->() const {
return &it_->get_public();
}
NodeT *get() {
return it_;
}
bool operator==(const Iterator &other) const {
DCHECK(other.it_ == nullptr);
return it_ == nullptr;
}
bool operator!=(const Iterator &other) const {
DCHECK(other.it_ == nullptr);
return it_ != nullptr;
}
Iterator() = default;
Iterator(NodeT *it, NodeT *begin, NodeT *end) : it_(it), begin_(begin), start_(it), end_(end) {
}
private:
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NodeT *it_ = nullptr;
NodeT *begin_ = nullptr;
NodeT *start_ = nullptr;
NodeT *end_ = nullptr;
};
struct ConstIterator {
using iterator_category = std::forward_iterator_tag;
using difference_type = std::ptrdiff_t;
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using value_type = FlatHashTable::value_type;
using pointer = const value_type *;
using reference = const value_type &;
ConstIterator &operator++() {
++it_;
return *this;
}
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reference operator*() const {
return *it_;
}
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pointer operator->() const {
return &*it_;
}
bool operator==(const ConstIterator &other) const {
return it_ == other.it_;
}
bool operator!=(const ConstIterator &other) const {
return it_ != other.it_;
}
ConstIterator() = default;
ConstIterator(Iterator it) : it_(std::move(it)) {
}
private:
Iterator it_;
};
using iterator = Iterator;
using const_iterator = ConstIterator;
struct NodePointer {
value_type &operator*() {
return it_->get_public();
}
const value_type &operator*() const {
return it_->get_public();
}
value_type *operator->() {
return &it_->get_public();
}
const value_type *operator->() const {
return &it_->get_public();
}
NodeT *get() {
return it_;
}
bool operator==(const Iterator &) const {
return it_ == nullptr;
}
bool operator!=(const Iterator &) const {
return it_ != nullptr;
}
explicit NodePointer(NodeT *it) : it_(it) {
}
private:
NodeT *it_ = nullptr;
};
struct ConstNodePointer {
const value_type &operator*() const {
return it_->get_public();
}
const value_type *operator->() const {
return &it_->get_public();
}
bool operator==(const ConstIterator &) const {
return it_ == nullptr;
}
bool operator!=(const ConstIterator &) const {
return it_ != nullptr;
}
const NodeT *get() const {
return it_;
}
explicit ConstNodePointer(const NodeT *it) : it_(it) {
}
private:
const NodeT *it_ = nullptr;
};
FlatHashTable() = default;
FlatHashTable(const FlatHashTable &other) = delete;
FlatHashTable &operator=(const FlatHashTable &other) = delete;
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FlatHashTable(std::initializer_list<NodeT> nodes) {
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if (nodes.size() == 0) {
return;
}
reserve(nodes.size());
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uint32 used_nodes = 0;
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for (auto &new_node : nodes) {
CHECK(!new_node.empty());
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auto bucket = calc_bucket(new_node.key());
while (true) {
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auto &node = nodes_[bucket];
if (node.empty()) {
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node.copy_from(new_node);
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used_nodes++;
break;
}
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if (EqT()(node.key(), new_node.key())) {
break;
}
next_bucket(bucket);
}
}
used_node_count_ = used_nodes;
}
FlatHashTable(FlatHashTable &&other) noexcept
: nodes_(other.nodes_)
, used_node_count_(other.used_node_count_)
, bucket_count_mask_(other.bucket_count_mask_)
, bucket_count_(other.bucket_count_)
, begin_bucket_(other.begin_bucket_) {
other.drop();
}
void operator=(FlatHashTable &&other) noexcept {
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clear();
nodes_ = other.nodes_;
used_node_count_ = other.used_node_count_;
bucket_count_mask_ = other.bucket_count_mask_;
bucket_count_ = other.bucket_count_;
begin_bucket_ = other.begin_bucket_;
other.drop();
}
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~FlatHashTable() {
clear_nodes(nodes_);
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}
void swap(FlatHashTable &other) noexcept {
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std::swap(nodes_, other.nodes_);
std::swap(used_node_count_, other.used_node_count_);
std::swap(bucket_count_mask_, other.bucket_count_mask_);
std::swap(bucket_count_, other.bucket_count_);
std::swap(begin_bucket_, other.begin_bucket_);
}
uint32 bucket_count() const {
return bucket_count_;
}
NodePointer find(const KeyT &key) {
return NodePointer(find_impl(key));
}
ConstNodePointer find(const KeyT &key) const {
return ConstNodePointer(const_cast<FlatHashTable *>(this)->find_impl(key));
}
size_t size() const {
return used_node_count_;
}
bool empty() const {
return used_node_count_ == 0;
}
Iterator begin() {
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return create_iterator(begin_impl());
}
Iterator end() {
return Iterator();
}
ConstIterator begin() const {
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return ConstIterator(const_cast<FlatHashTable *>(this)->begin());
}
ConstIterator end() const {
return ConstIterator();
}
void reserve(size_t size) {
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if (size == 0) {
return;
}
CHECK(size <= (1u << 29));
uint32 want_size = detail::normalize_flat_hash_table_size(static_cast<uint32>(size) * 5 / 3 + 1);
if (want_size > bucket_count()) {
resize(want_size);
}
}
template <class... ArgsT>
std::pair<NodePointer, bool> emplace(KeyT key, ArgsT &&...args) {
CHECK(!is_hash_table_key_empty(key));
if (unlikely(bucket_count_mask_ == 0)) {
CHECK(used_node_count_ == 0);
resize(8);
}
auto bucket = calc_bucket(key);
while (true) {
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auto &node = nodes_[bucket];
if (node.empty()) {
if (unlikely(used_node_count_ * 5 >= bucket_count_mask_ * 3)) {
resize(2 * bucket_count_);
CHECK(used_node_count_ * 5 < bucket_count_mask_ * 3);
return emplace(std::move(key), std::forward<ArgsT>(args)...);
}
invalidate_iterators();
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node.emplace(std::move(key), std::forward<ArgsT>(args)...);
used_node_count_++;
return {NodePointer(&node), true};
}
if (EqT()(node.key(), key)) {
return {NodePointer(&node), false};
}
next_bucket(bucket);
}
}
std::pair<NodePointer, bool> insert(KeyT key) {
return emplace(std::move(key));
}
template <class ItT>
void insert(ItT begin, ItT end) {
for (; begin != end; ++begin) {
emplace(*begin);
}
}
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template <class T = typename NodeT::second_type>
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T &operator[](const KeyT &key) {
return emplace(key).first->second;
}
size_t erase(const KeyT &key) {
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auto *node = find_impl(key);
if (node == nullptr) {
return 0;
}
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erase_node(node);
try_shrink();
return 1;
}
size_t count(const KeyT &key) const {
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return const_cast<FlatHashTable *>(this)->find_impl(key) != nullptr;
}
void clear() {
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if (nodes_ != nullptr) {
clear_nodes(nodes_);
drop();
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}
}
void erase(Iterator it) {
DCHECK(it != end());
erase_node(it.get());
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try_shrink();
}
void erase(NodePointer it) {
DCHECK(it != end());
erase_node(it.get());
try_shrink();
}
template <class F>
void remove_if(F &&f) {
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if (empty()) {
return;
}
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auto it = begin_impl();
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auto end = nodes_ + bucket_count();
while (it != end && !it->empty()) {
++it;
}
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if (it == end) {
do {
--it;
} while (!it->empty());
}
auto first_empty = it;
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while (it != end) {
if (!it->empty() && f(it->get_public())) {
erase_node(it);
} else {
++it;
}
}
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for (it = nodes_; it != first_empty;) {
if (!it->empty() && f(it->get_public())) {
erase_node(it);
} else {
++it;
}
}
try_shrink();
}
private:
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NodeT *nodes_ = nullptr;
uint32 used_node_count_ = 0;
uint32 bucket_count_mask_ = 0;
uint32 bucket_count_ = 0;
uint32 begin_bucket_ = 0;
void drop() {
nodes_ = nullptr;
used_node_count_ = 0;
bucket_count_mask_ = 0;
bucket_count_ = 0;
begin_bucket_ = 0;
}
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NodeT *begin_impl() {
if (empty()) {
return nullptr;
}
if (begin_bucket_ == INVALID_BUCKET) {
begin_bucket_ = detail::get_random_flat_hash_table_bucket(bucket_count_mask_);
while (nodes_[begin_bucket_].empty()) {
next_bucket(begin_bucket_);
}
}
return nodes_ + begin_bucket_;
}
NodeT *find_impl(const KeyT &key) {
if (unlikely(nodes_ == nullptr) || is_hash_table_key_empty(key)) {
return nullptr;
}
auto bucket = calc_bucket(key);
while (true) {
auto &node = nodes_[bucket];
if (node.empty()) {
return nullptr;
}
if (EqT()(node.key(), key)) {
return &node;
}
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next_bucket(bucket);
}
}
void try_shrink() {
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DCHECK(nodes_ != nullptr);
if (unlikely(used_node_count_ * 10 < bucket_count_mask_ && bucket_count_mask_ > 7)) {
resize(detail::normalize_flat_hash_table_size((used_node_count_ + 1) * 5 / 3 + 1));
}
invalidate_iterators();
}
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uint32 calc_bucket(const KeyT &key) const {
return HashT()(key) & bucket_count_mask_;
}
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inline void next_bucket(uint32 &bucket) const {
bucket = (bucket + 1) & bucket_count_mask_;
}
void resize(uint32 new_size) {
if (unlikely(nodes_ == nullptr)) {
allocate_nodes(new_size);
used_node_count_ = 0;
return;
}
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auto old_nodes = nodes_;
uint32 old_size = used_node_count_;
uint32 old_bucket_count = bucket_count_;
allocate_nodes(new_size);
used_node_count_ = old_size;
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auto old_nodes_end = old_nodes + old_bucket_count;
for (NodeT *old_node = old_nodes; old_node != old_nodes_end; ++old_node) {
if (old_node->empty()) {
continue;
}
auto bucket = calc_bucket(old_node->key());
while (!nodes_[bucket].empty()) {
next_bucket(bucket);
}
nodes_[bucket] = std::move(*old_node);
}
clear_nodes(old_nodes);
}
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void erase_node(NodeT *it) {
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DCHECK(nodes_ <= it && static_cast<size_t>(it - nodes_) < bucket_count());
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it->clear();
used_node_count_--;
const auto bucket_count = bucket_count_;
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const auto *end = nodes_ + bucket_count;
for (auto *test_node = it + 1; test_node != end; test_node++) {
if (likely(test_node->empty())) {
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return;
}
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auto want_node = nodes_ + calc_bucket(test_node->key());
if (want_node <= it || want_node > test_node) {
*it = std::move(*test_node);
it = test_node;
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}
}
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auto empty_i = static_cast<uint32>(it - nodes_);
auto empty_bucket = empty_i;
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for (uint32 test_i = bucket_count;; test_i++) {
auto test_bucket = test_i - bucket_count_;
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if (nodes_[test_bucket].empty()) {
return;
}
auto want_i = calc_bucket(nodes_[test_bucket].key());
if (want_i < empty_i) {
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want_i += bucket_count;
}
if (want_i <= empty_i || want_i > test_i) {
nodes_[empty_bucket] = std::move(nodes_[test_bucket]);
empty_i = test_i;
empty_bucket = test_bucket;
}
}
}
Iterator create_iterator(NodeT *node) {
return Iterator(node, nodes_, nodes_ + bucket_count());
}
void invalidate_iterators() {
begin_bucket_ = INVALID_BUCKET;
}
};
} // namespace td