include/tsl/robin_map.h

/**
 * MIT License
 *
 * Copyright (c) 2017 Thibaut Goetghebuer-Planchon <tessil@gmx.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#ifndef TSL_ROBIN_MAP_H
#define TSL_ROBIN_MAP_H


#include <cstddef>
#include <functional>
#include <initializer_list>
#include <memory>
#include <type_traits>
#include <utility>
#include "robin_hash.h"


namespace tsl {


/**
 * Implementation of a hash map using open-addressing and the robin hood hashing algorithm with backward shift deletion.
 *
 * For operations modifying the hash map (insert, erase, rehash, ...), the strong exception guarantee
 * is only guaranteed when the expression `std::is_nothrow_swappable<std::pair<Key, T>>::value &&
 * std::is_nothrow_move_constructible<std::pair<Key, T>>::value` is true, otherwise if an exception
 * is thrown during the swap or the move, the hash map may end up in a undefined state. Per the standard
 * a `Key` or `T` with a noexcept copy constructor and no move constructor also satisfies the
 * `std::is_nothrow_move_constructible<std::pair<Key, T>>::value` criterion (and will thus guarantee the
 * strong exception for the map).
 *
 * When `StoreHash` is true, 32 bits of the hash are stored alongside the values. It can improve
 * the performance during lookups if the `KeyEqual` function takes time (if it engenders a cache-miss for example)
 * as we then compare the stored hashes before comparing the keys. When `tsl::rh::power_of_two_growth_policy` is used
 * as `GrowthPolicy`, it may also speed-up the rehash process as we can avoid to recalculate the hash.
 * When it is detected that storing the hash will not incur any memory penalty due to alignment (i.e.
 * `sizeof(tsl::detail_robin_hash::bucket_entry<ValueType, true>) ==
 * sizeof(tsl::detail_robin_hash::bucket_entry<ValueType, false>)`) and `tsl::rh::power_of_two_growth_policy` is
 * used, the hash will be stored even if `StoreHash` is false so that we can speed-up the rehash (but it will
 * not be used on lookups unless `StoreHash` is true).
 *
 * `GrowthPolicy` defines how the map grows and consequently how a hash value is mapped to a bucket.
 * By default the map uses `tsl::rh::power_of_two_growth_policy`. This policy keeps the number of buckets
 * to a power of two and uses a mask to map the hash to a bucket instead of the slow modulo.
 * Other growth policies are available and you may define your own growth policy,
 * check `tsl::rh::power_of_two_growth_policy` for the interface.
 *
 * `std::pair<Key, T>` must be swappable.
 *
 * `Key` and `T` must be copy and/or move constructible.
 *
 * If the destructor of `Key` or `T` throws an exception, the behaviour of the class is undefined.
 *
 * Iterators invalidation:
 *  - clear, operator=, reserve, rehash: always invalidate the iterators.
 *  - insert, emplace, emplace_hint, operator[]: if there is an effective insert, invalidate the iterators.
 *  - erase: always invalidate the iterators.
 */
template<class Key,
         class T,
         class Hash = std::hash<Key>,
         class KeyEqual = std::equal_to<Key>,
         class Allocator = std::allocator<std::pair<Key, T>>,
         bool StoreHash = false,
         class GrowthPolicy = tsl::rh::power_of_two_growth_policy<2>>
class robin_map {
private:
    template<typename U>
    using has_is_transparent = tsl::detail_robin_hash::has_is_transparent<U>;

    class KeySelect {
    public:
        using key_type = Key;

        const key_type& operator()(const std::pair<Key, T>& key_value) const noexcept {
            return key_value.first;
        }

        key_type& operator()(std::pair<Key, T>& key_value) noexcept {
            return key_value.first;
        }
    };

    class ValueSelect {
    public:
        using value_type = T;

        const value_type& operator()(const std::pair<Key, T>& key_value) const noexcept {
            return key_value.second;
        }

        value_type& operator()(std::pair<Key, T>& key_value) noexcept {
            return key_value.second;
        }
    };

    using ht = detail_robin_hash::robin_hash<std::pair<Key, T>, KeySelect, ValueSelect,
                                             Hash, KeyEqual, Allocator, StoreHash, GrowthPolicy>;

public:
    using key_type = typename ht::key_type;
    using mapped_type = T;
    using value_type = typename ht::value_type;
    using size_type = typename ht::size_type;
    using difference_type = typename ht::difference_type;
    using hasher = typename ht::hasher;
    using key_equal = typename ht::key_equal;
    using allocator_type = typename ht::allocator_type;
    using reference = typename ht::reference;
    using const_reference = typename ht::const_reference;
    using pointer = typename ht::pointer;
    using const_pointer = typename ht::const_pointer;
    using iterator = typename ht::iterator;
    using const_iterator = typename ht::const_iterator;


public:
    /*
     * Constructors
     */
    robin_map(): robin_map(ht::DEFAULT_INIT_BUCKETS_SIZE) {
    }

    explicit robin_map(size_type bucket_count,
                       const Hash& hash = Hash(),
                       const KeyEqual& equal = KeyEqual(),
                       const Allocator& alloc = Allocator()):
                m_ht(bucket_count, hash, equal, alloc)
    {
    }

    robin_map(size_type bucket_count,
              const Allocator& alloc): robin_map(bucket_count, Hash(), KeyEqual(), alloc)
    {
    }

    robin_map(size_type bucket_count,
              const Hash& hash,
              const Allocator& alloc): robin_map(bucket_count, hash, KeyEqual(), alloc)
    {
    }

    explicit robin_map(const Allocator& alloc): robin_map(ht::DEFAULT_INIT_BUCKETS_SIZE, alloc) {
    }

    template<class InputIt>
    robin_map(InputIt first, InputIt last,
              size_type bucket_count = ht::DEFAULT_INIT_BUCKETS_SIZE,
              const Hash& hash = Hash(),
              const KeyEqual& equal = KeyEqual(),
              const Allocator& alloc = Allocator()): robin_map(bucket_count, hash, equal, alloc)
    {
        insert(first, last);
    }

    template<class InputIt>
    robin_map(InputIt first, InputIt last,
              size_type bucket_count,
              const Allocator& alloc): robin_map(first, last, bucket_count, Hash(), KeyEqual(), alloc)
    {
    }

    template<class InputIt>
    robin_map(InputIt first, InputIt last,
              size_type bucket_count,
              const Hash& hash,
              const Allocator& alloc): robin_map(first, last, bucket_count, hash, KeyEqual(), alloc)
    {
    }

    robin_map(std::initializer_list<value_type> init,
              size_type bucket_count = ht::DEFAULT_INIT_BUCKETS_SIZE,
              const Hash& hash = Hash(),
              const KeyEqual& equal = KeyEqual(),
              const Allocator& alloc = Allocator()):
          robin_map(init.begin(), init.end(), bucket_count, hash, equal, alloc)
    {
    }

    robin_map(std::initializer_list<value_type> init,
              size_type bucket_count,
              const Allocator& alloc):
          robin_map(init.begin(), init.end(), bucket_count, Hash(), KeyEqual(), alloc)
    {
    }

    robin_map(std::initializer_list<value_type> init,
              size_type bucket_count,
              const Hash& hash,
              const Allocator& alloc):
          robin_map(init.begin(), init.end(), bucket_count, hash, KeyEqual(), alloc)
    {
    }

    robin_map& operator=(std::initializer_list<value_type> ilist) {
        m_ht.clear();

        m_ht.reserve(ilist.size());
        m_ht.insert(ilist.begin(), ilist.end());

        return *this;
    }

    allocator_type get_allocator() const { return m_ht.get_allocator(); }


    /*
     * Iterators
     */
    iterator begin() noexcept { return m_ht.begin(); }
    const_iterator begin() const noexcept { return m_ht.begin(); }
    const_iterator cbegin() const noexcept { return m_ht.cbegin(); }

    iterator end() noexcept { return m_ht.end(); }
    const_iterator end() const noexcept { return m_ht.end(); }
    const_iterator cend() const noexcept { return m_ht.cend(); }


    /*
     * Capacity
     */
    bool empty() const noexcept { return m_ht.empty(); }
    size_type size() const noexcept { return m_ht.size(); }
    size_type max_size() const noexcept { return m_ht.max_size(); }

    /*
     * Modifiers
     */
    void clear() noexcept { m_ht.clear(); }


    std::pair<iterator, bool> insert(const value_type& value) {
        return m_ht.insert(value);
    }

    template<class P, typename std::enable_if<std::is_constructible<value_type, P&&>::value>::type* = nullptr>
    std::pair<iterator, bool> insert(P&& value) {
        return m_ht.emplace(std::forward<P>(value));
    }

    std::pair<iterator, bool> insert(value_type&& value) {
        return m_ht.insert(std::move(value));
    }


    iterator insert(const_iterator hint, const value_type& value) {
        return m_ht.insert_hint(hint, value);
    }

    template<class P, typename std::enable_if<std::is_constructible<value_type, P&&>::value>::type* = nullptr>
    iterator insert(const_iterator hint, P&& value) {
        return m_ht.emplace_hint(hint, std::forward<P>(value));
    }

    iterator insert(const_iterator hint, value_type&& value) {
        return m_ht.insert_hint(hint, std::move(value));
    }


    template<class InputIt>
    void insert(InputIt first, InputIt last) {
        m_ht.insert(first, last);
    }

    void insert(std::initializer_list<value_type> ilist) {
        m_ht.insert(ilist.begin(), ilist.end());
    }


    template<class M>
    std::pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj) {
        return m_ht.insert_or_assign(k, std::forward<M>(obj));
    }

    template<class M>
    std::pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj) {
        return m_ht.insert_or_assign(std::move(k), std::forward<M>(obj));
    }

    template<class M>
    iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj) {
        return m_ht.insert_or_assign(hint, k, std::forward<M>(obj));
    }

    template<class M>
    iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj) {
        return m_ht.insert_or_assign(hint, std::move(k), std::forward<M>(obj));
    }


    /**
     * Due to the way elements are stored, emplace will need to move or copy the key-value once.
     * The method is equivalent to insert(value_type(std::forward<Args>(args)...));
     *
     * Mainly here for compatibility with the std::unordered_map interface.
     */
    template<class... Args>
    std::pair<iterator, bool> emplace(Args&&... args) {
        return m_ht.emplace(std::forward<Args>(args)...);
    }


    /**
     * Due to the way elements are stored, emplace_hint will need to move or copy the key-value once.
     * The method is equivalent to insert(hint, value_type(std::forward<Args>(args)...));
     *
     * Mainly here for compatibility with the std::unordered_map interface.
     */
    template<class... Args>
    iterator emplace_hint(const_iterator hint, Args&&... args) {
        return m_ht.emplace_hint(hint, std::forward<Args>(args)...);
    }


    template<class... Args>
    std::pair<iterator, bool> try_emplace(const key_type& k, Args&&... args) {
        return m_ht.try_emplace(k, std::forward<Args>(args)...);
    }

    template<class... Args>
    std::pair<iterator, bool> try_emplace(key_type&& k, Args&&... args) {
        return m_ht.try_emplace(std::move(k), std::forward<Args>(args)...);
    }

    template<class... Args>
    iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args) {
        return m_ht.try_emplace_hint(hint, k, std::forward<Args>(args)...);
    }

    template<class... Args>
    iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args) {
        return m_ht.try_emplace_hint(hint, std::move(k), std::forward<Args>(args)...);
    }


    iterator erase(iterator pos) { return m_ht.erase(pos); }
    iterator erase(const_iterator pos) { return m_ht.erase(pos); }
    iterator erase(const_iterator first, const_iterator last) { return m_ht.erase(first, last); }
    size_type erase(const key_type& key) { return m_ht.erase(key); }

    /**
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup to the value if you already have the hash.
     */
    size_type erase(const key_type& key, std::size_t precalculated_hash) {
        return m_ht.erase(key, precalculated_hash);
    }

    /**
     * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
     * If so, K must be hashable and comparable to Key.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    size_type erase(const K& key) { return m_ht.erase(key); }

    /**
     * @copydoc erase(const K& key)
     *
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup to the value if you already have the hash.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    size_type erase(const K& key, std::size_t precalculated_hash) {
        return m_ht.erase(key, precalculated_hash);
    }


    void swap(robin_map& other) { other.m_ht.swap(m_ht); }


    /*
     * Lookup
     */
    T& at(const Key& key) { return m_ht.at(key); }

    /**
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    T& at(const Key& key, std::size_t precalculated_hash) { return m_ht.at(key, precalculated_hash); }


    const T& at(const Key& key) const { return m_ht.at(key); }

    /**
     * @copydoc at(const Key& key, std::size_t precalculated_hash)
     */
    const T& at(const Key& key, std::size_t precalculated_hash) const { return m_ht.at(key, precalculated_hash); }


    /**
     * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
     * If so, K must be hashable and comparable to Key.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    T& at(const K& key) { return m_ht.at(key); }

    /**
     * @copydoc at(const K& key)
     *
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    T& at(const K& key, std::size_t precalculated_hash) { return m_ht.at(key, precalculated_hash); }


    /**
     * @copydoc at(const K& key)
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    const T& at(const K& key) const { return m_ht.at(key); }

    /**
     * @copydoc at(const K& key, std::size_t precalculated_hash)
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    const T& at(const K& key, std::size_t precalculated_hash) const { return m_ht.at(key, precalculated_hash); }


    T& operator[](const Key& key) { return m_ht[key]; }
    T& operator[](Key&& key) { return m_ht[std::move(key)]; }


    size_type count(const Key& key) const { return m_ht.count(key); }

    /**
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    size_type count(const Key& key, std::size_t precalculated_hash) const {
        return m_ht.count(key, precalculated_hash);
    }

    /**
     * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
     * If so, K must be hashable and comparable to Key.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    size_type count(const K& key) const { return m_ht.count(key); }

    /**
     * @copydoc count(const K& key) const
     *
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    size_type count(const K& key, std::size_t precalculated_hash) const { return m_ht.count(key, precalculated_hash); }


    iterator find(const Key& key) { return m_ht.find(key); }

    /**
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    iterator find(const Key& key, std::size_t precalculated_hash) { return m_ht.find(key, precalculated_hash); }

    const_iterator find(const Key& key) const { return m_ht.find(key); }

    /**
     * @copydoc find(const Key& key, std::size_t precalculated_hash)
     */
    const_iterator find(const Key& key, std::size_t precalculated_hash) const {
        return m_ht.find(key, precalculated_hash);
    }

    /**
     * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
     * If so, K must be hashable and comparable to Key.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    iterator find(const K& key) { return m_ht.find(key); }

    /**
     * @copydoc find(const K& key)
     *
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    iterator find(const K& key, std::size_t precalculated_hash) { return m_ht.find(key, precalculated_hash); }

    /**
     * @copydoc find(const K& key)
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    const_iterator find(const K& key) const { return m_ht.find(key); }

    /**
     * @copydoc find(const K& key)
     *
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    const_iterator find(const K& key, std::size_t precalculated_hash) const {
        return m_ht.find(key, precalculated_hash);
    }


    bool contains(const Key& key) const { return m_ht.contains(key); }

    /**
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    bool contains(const Key& key, std::size_t precalculated_hash) const {
        return m_ht.contains(key, precalculated_hash);
    }

    /**
     * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
     * If so, K must be hashable and comparable to Key.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    bool contains(const K& key) const { return m_ht.contains(key); }

    /**
     * @copydoc contains(const K& key) const
     *
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    bool contains(const K& key, std::size_t precalculated_hash) const {
        return m_ht.contains(key, precalculated_hash);
    }


    std::pair<iterator, iterator> equal_range(const Key& key) { return m_ht.equal_range(key); }

    /**
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    std::pair<iterator, iterator> equal_range(const Key& key, std::size_t precalculated_hash) {
        return m_ht.equal_range(key, precalculated_hash);
    }

    std::pair<const_iterator, const_iterator> equal_range(const Key& key) const { return m_ht.equal_range(key); }

    /**
     * @copydoc equal_range(const Key& key, std::size_t precalculated_hash)
     */
    std::pair<const_iterator, const_iterator> equal_range(const Key& key, std::size_t precalculated_hash) const {
        return m_ht.equal_range(key, precalculated_hash);
    }

    /**
     * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
     * If so, K must be hashable and comparable to Key.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    std::pair<iterator, iterator> equal_range(const K& key) { return m_ht.equal_range(key); }


    /**
     * @copydoc equal_range(const K& key)
     *
     * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
     * as hash_function()(key). Useful to speed-up the lookup if you already have the hash.
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    std::pair<iterator, iterator> equal_range(const K& key, std::size_t precalculated_hash) {
        return m_ht.equal_range(key, precalculated_hash);
    }

    /**
     * @copydoc equal_range(const K& key)
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    std::pair<const_iterator, const_iterator> equal_range(const K& key) const { return m_ht.equal_range(key); }

    /**
     * @copydoc equal_range(const K& key, std::size_t precalculated_hash)
     */
    template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
    std::pair<const_iterator, const_iterator> equal_range(const K& key, std::size_t precalculated_hash) const {
        return m_ht.equal_range(key, precalculated_hash);
    }


    /*
     * Bucket interface
     */
    size_type bucket_count() const { return m_ht.bucket_count(); }
    size_type max_bucket_count() const { return m_ht.max_bucket_count(); }


    /*
     *  Hash policy
     */
    float load_factor() const { return m_ht.load_factor(); }

    float min_load_factor() const { return m_ht.min_load_factor(); }
    float max_load_factor() const { return m_ht.max_load_factor(); }

    /**
     * Set the `min_load_factor` to `ml`. When the `load_factor` of the map goes
     * below `min_load_factor` after some erase operations, the map will be
     * shrunk when an insertion occurs. The erase method itself never shrinks
     * the map.
     *
     * The default value of `min_load_factor` is 0.0f, the map never shrinks by default.
     */
    void min_load_factor(float ml) { m_ht.min_load_factor(ml); }
    void max_load_factor(float ml) { m_ht.max_load_factor(ml); }

    void rehash(size_type count) { m_ht.rehash(count); }
    void reserve(size_type count) { m_ht.reserve(count); }


    /*
     * Observers
     */
    hasher hash_function() const { return m_ht.hash_function(); }
    key_equal key_eq() const { return m_ht.key_eq(); }

    /*
     * Other
     */

    /**
     * Convert a const_iterator to an iterator.
     */
    iterator mutable_iterator(const_iterator pos) {
        return m_ht.mutable_iterator(pos);
    }

    friend bool operator==(const robin_map& lhs, const robin_map& rhs) {
        if(lhs.size() != rhs.size()) {
            return false;
        }

        for(const auto& element_lhs: lhs) {
            const auto it_element_rhs = rhs.find(element_lhs.first);
            if(it_element_rhs == rhs.cend() || element_lhs.second != it_element_rhs->second) {
                return false;
            }
        }

        return true;
    }

    friend bool operator!=(const robin_map& lhs, const robin_map& rhs) {
        return !operator==(lhs, rhs);
    }

    friend void swap(robin_map& lhs, robin_map& rhs) {
        lhs.swap(rhs);
    }

private:
    ht m_ht;
};


/**
 * Same as `tsl::robin_map<Key, T, Hash, KeyEqual, Allocator, StoreHash, tsl::rh::prime_growth_policy>`.
 */
template<class Key,
         class T,
         class Hash = std::hash<Key>,
         class KeyEqual = std::equal_to<Key>,
         class Allocator = std::allocator<std::pair<Key, T>>,
         bool StoreHash = false>
using robin_pg_map = robin_map<Key, T, Hash, KeyEqual, Allocator, StoreHash, tsl::rh::prime_growth_policy>;

} // end namespace tsl

#endif