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UnorderedMap.hpp
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UnorderedMap.hpp
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#ifndef UNORDERED_CONCURRENT_MAP_H
#define UNORDERED_CONCURRENT_MAP_H
#include <shared_mutex>
#include <unordered_map>
namespace concurrency {
// This class provides a thread-safe unordered map with most of the same functionality as
// std::unordered_map. However, iterator access has been removed in order to preserve
// thread-safety. No direct access to begin() or end() iterators is provided. Iterators
// have also been removed from the return type of any function which typically includes
// them.
//
// Aside from the above, functions which behave differently than their std::unordered_map
// counterpart of the same name are documented with comments, as are functions that
// do not exist for std::unordered_map.
//
// https://en.cppreference.com/w/cpp/container/unordered_map
template <class Key, class Val, class Hash = std::hash<Key>, class Pred = std::equal_to<Key>, class Allocator = std::allocator<std::pair<const Key, Val>>>
class UnorderedMap {
public:
// ------------------------------ Member types ------------------------------ //
using mutex_type = std::shared_mutex;
using read_lock = std::shared_lock<mutex_type>;
using write_lock = std::unique_lock<mutex_type>;
using self_type = UnorderedMap<Key, Val, Hash, Pred, Allocator>;
using internal_map_type = std::unordered_map<Key, Val, Hash, Pred, Allocator>;
using key_type = typename internal_map_type::key_type;
using mapped_type = typename internal_map_type::mapped_type;
using value_type = typename internal_map_type::value_type;
using size_type = typename internal_map_type::size_type;
using difference_type = typename internal_map_type::difference_type;
using hasher = typename internal_map_type::hasher;
using key_equal = typename internal_map_type::key_equal;
using allocator_type = typename internal_map_type::allocator_type;
using reference = typename internal_map_type::reference;
using const_reference = typename internal_map_type::const_reference;
using pointer = typename internal_map_type::pointer;
using const_pointer = typename internal_map_type::const_pointer;
using iterator = typename internal_map_type::iterator;
using const_iterator = typename internal_map_type::const_iterator;
using local_iterator = typename internal_map_type::local_iterator;
using const_local_iterator = typename internal_map_type::const_local_iterator;
using node_type = typename internal_map_type::node_type;
// This member type intentionally excluded, as it is not used in this implementation.
// using insert_return_type = typename internal_map_type::insert_return_type;
// ------------------------------ Constructors ------------------------------ //
UnorderedMap() = default;
UnorderedMap(const UnorderedMap &other) {
auto lock = lock_for_writing();
m_map = std::move(other.data());
}
UnorderedMap(UnorderedMap &&other) {
auto lock = lock_for_writing();
m_map = std::move(other.data());
}
UnorderedMap(std::initializer_list<value_type> ilist) { insert(ilist); }
UnorderedMap &operator=(const UnorderedMap &other) {
auto lock = lock_for_writing();
this->m_map = other.data();
return *this;
}
UnorderedMap &operator=(UnorderedMap &&other) noexcept {
auto lock = lock_for_writing();
this->m_map = std::move(other.data());
return *this;
}
UnorderedMap &operator=(std::initializer_list<value_type> ilist) {
this->insert(ilist);
return *this;
}
~UnorderedMap() = default;
allocator_type get_allocator() const { return m_map.get_allocator(); }
// ------------------------------- Iterators -------------------------------- //
/*
begin(), end(), cbegin(), and cend() iterators are not supported due to the footgun they present
to concurrent access.
*/
// -------------------------------- Capacity -------------------------------- //
bool empty() const noexcept {
auto l = lock_for_reading();
return m_map.empty();
}
size_type size() const noexcept {
auto l = lock_for_reading();
return m_map.size();
}
size_type max_size() const noexcept { return m_map.max_size(); }
// ------------------------------- Modifiers -------------------------------- //
void clear() noexcept {
auto lock = lock_for_writing();
m_map.clear();
}
bool insert(const value_type &value) {
auto lock = lock_for_writing();
return m_map.insert(value).second;
}
bool insert(value_type &&value) {
auto lock = lock_for_writing();
return m_map.insert(value).second;
}
template <class P>
bool insert(P &&value) {
auto lock = lock_for_writing();
return m_map.insert(value).second;
}
void insert(std::initializer_list<value_type> ilist) {
auto lock = lock_for_writing();
(void) m_map.insert(ilist);
}
bool insert(node_type &&nh) {
auto lock = lock_for_writing();
return m_map.insert(std::move(nh)).inserted;
}
template <class M>
bool insert_or_assign(const Key &k, M &&obj) {
auto lock = lock_for_writing();
return m_map.insert_or_assign(k, obj).second;
}
template <class M>
bool insert_or_assign(Key &&k, M &&obj) {
auto lock = lock_for_writing();
return m_map.insert_or_assign(k, obj).second;
}
template <class... Args>
bool emplace(Args &&...args) {
auto lock = lock_for_writing();
return m_map.emplace(args...).second;
}
template <class... Args>
bool try_emplace(const Key &k, Args &&...args) {
auto lock = lock_for_writing();
return m_map.try_emplace(k, args...).second;
}
template <class... Args>
bool try_emplace(Key &&k, Args &&...args) {
auto lock = lock_for_writing();
return m_map.try_emplace(k, args...).second;
}
size_type erase(const Key &key) {
auto lock = lock_for_writing();
return m_map.erase(key);
}
void swap(UnorderedMap<Key, Val, Hash, Pred, Allocator> &other) noexcept {
auto lhs_lock = this->lock_for_writing();
auto rhs_lock = other.lock_for_writing();
this->m_map.swap(other.m_map);
}
void swap(internal_map_type &other) noexcept {
auto lock = lock_for_writing();
m_map.swap(other);
}
node_type extract(const Key &k) {
auto lock = lock_for_writing();
return m_map.extract(k);
}
void merge(internal_map_type &source) {
auto lock = lock_for_writing();
m_map.merge(source);
}
void merge(internal_map_type &&source) {
auto lock = lock_for_writing();
m_map.merge(source);
}
void merge(std::unordered_multimap<Key, Val, Hash, Pred, Allocator> &source) {
auto lock = lock_for_writing();
m_map.merge(source);
}
void merge(std::unordered_multimap<Key, Val, Hash, Pred, Allocator> &&source) {
auto lock = lock_for_writing();
m_map.merge(source);
}
void merge(UnorderedMap<Key, Val, Hash, Pred, Allocator> &source) {
for (auto const &el: source.data()) {
if (find(el.first)) continue;
(void) insert(std::move(source.extract(el.first)));
}
}
void merge(UnorderedMap<Key, Val, Hash, Pred, Allocator> &&source) {
for (auto const &el: source.data()) {
if (find(el.first)) continue;
(void) insert(std::move(source.extract(el.first)));
}
}
// ------------------------------ Accessors --------------------------------- //
// Returns a copy of the element mapped to
// the provided key. Does bounds checking.
Val at(const Key &key) const {
auto lock = lock_for_reading();
return m_map.at(key);
}
// Returns a copy of the element mapped to
// the provided key. Does bounds checking.
Val at(const Key &&key) const {
auto lock = lock_for_reading();
return m_map.at(key);
}
// Returns a copy of the element mapped to
// the provided key. If no element is present,
// a new one is default constructed.
Val operator[](const Key &key) {
if (this->find(key)) return this->at(key);
auto lock = lock_for_writing();
return m_map[key];
}
// Returns a copy of the element mapped to
// the provided key. If no element is present,
// a new one is default constructed.
Val operator[](Key &&key) {
if (this->find(key)) return this->at(key);
auto lock = lock_for_writing();
return m_map[key];
}
size_type count(const Key &key) const {
auto lock = lock_for_reading();
return m_map.count(key);
}
// Returns a bool indicating whether or not the
// provided key is present in the map.
bool find(const Key &key) const {
auto lock = lock_for_reading();
return m_map.find(key) != m_map.end();
}
// Returns a non-thread-safe copy of the underlying map.
internal_map_type data() const {
auto lock = lock_for_reading();
return m_map;
}
// --------------------------- Bucket Interface ----------------------------- //
size_type bucket_count() const {
auto lock = lock_for_reading();
return m_map.bucket_count();
}
size_type max_bucket_count() const { return m_map.max_bucket_count(); }
size_type bucket_size(size_type n) const {
auto lock = lock_for_reading();
return m_map.bucket_size(n);
}
size_type bucket(const Key &key) const {
auto lock = lock_for_reading();
return m_map.bucket(key);
}
// ------------------------------ Hash Policy ------------------------------- //
float load_factor() const {
auto lock = lock_for_reading();
return m_map.load_factor();
}
float max_load_factor() const {
auto lock = lock_for_reading();
return m_map.max_load_factor();
}
void max_load_factor(float ml) {
auto lock = lock_for_writing();
m_map.max_load_factor(ml);
}
void rehash(size_type count) {
auto lock = lock_for_writing();
m_map.rehash(count);
}
void reserve(size_type count) {
auto lock = lock_for_writing();
m_map.reserve(count);
}
// ------------------------------- Observers -------------------------------- //
hasher hash_function() const { return m_map.hash_function(); }
key_equal key_eq() const { return m_map.key_eq(); }
private:
// Returns a locked read_lock that prevents concurrent write access to
// the underlying map.
read_lock lock_for_reading() const { return read_lock(m_mutex); }
// Returns a locked write_lock that prevents concurrent access to the
// underlying map.
write_lock lock_for_writing() const { return write_lock(m_mutex); }
mutable mutex_type m_mutex{};
internal_map_type m_map{};
};
template <class Key, class T, class Hash, class KeyEqual, class Alloc>
bool operator==(const ::concurrency::UnorderedMap<Key, T, Hash, KeyEqual, Alloc> &lhs, const ::concurrency::UnorderedMap<Key, T, Hash, KeyEqual, Alloc> &rhs) {
return lhs.data() == rhs.data();
}
template <class Key, class T, class Hash, class KeyEqual, class Alloc>
bool operator!=(const ::concurrency::UnorderedMap<Key, T, Hash, KeyEqual, Alloc> &lhs, const ::concurrency::UnorderedMap<Key, T, Hash, KeyEqual, Alloc> &rhs) {
return !(lhs == rhs);
}
template <class Key, class T, class Hash, class KeyEqual, class Alloc>
bool operator==(const ::concurrency::UnorderedMap<Key, T, Hash, KeyEqual, Alloc> &lhs, const ::concurrency::UnorderedMap<Key, T, Hash, KeyEqual, Alloc> &&rhs) {
return lhs.data() == rhs.data();
}
template <class Key, class T, class Hash, class KeyEqual, class Alloc>
bool operator!=(const ::concurrency::UnorderedMap<Key, T, Hash, KeyEqual, Alloc> &lhs, const ::concurrency::UnorderedMap<Key, T, Hash, KeyEqual, Alloc> &&rhs) {
return !(lhs == rhs);
}
// Specializes the std::swap algorithm for ::concurrency::UnorderedMap. Swaps the contents of lhs and rhs. Calls lhs.swap(rhs).
template <class Key, class T, class Hash, class KeyEqual, class Alloc>
void swap(::concurrency::UnorderedMap<Key, T, Hash, KeyEqual, Alloc> &lhs, ::concurrency::UnorderedMap<Key, T, Hash, KeyEqual, Alloc> &rhs) noexcept {
lhs.swap(rhs);
}
} // namespace concurrency
#endif // UNORDERED_CONCURRENT_MAP_H