robin_map.h

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/**
 * MIT License
 *
 * Copyright (c) 2017, 2022 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);
    }
 
    /**
     * 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); }
 
    /**
     */
    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);
    }
 
    /**
     * 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);
    }
 
    /**
     */
    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);
    }
 
    /**
     */
    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);
    }
 
    /**
     * 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); }
 
    /**
     */
    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);
    }
 
    /**
     * 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);
    }
 
    /**
     */
    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);
    }
 
    /**
     * 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);
    }
 
    /**
     * 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);
    }
 
    /**
     */
    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);
    }
 
    /**
     * 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);
    }
 
    /**
     */
    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);
    }
 
    /**
     */
    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 my_count) { m_ht.rehash(my_count); }
    void reserve(size_type my_count) { m_ht.reserve(my_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); }
 
    /**
     * Serialize the map through the `serializer` parameter.
     *
     * The `serializer` parameter must be a function object that supports the
     * following call:
     *  - `template<typename U> void operator()(const U& value);` where the types
     * `std::int16_t`, `std::uint32_t`, `std::uint64_t`, `float` and
     * `std::pair<Key, T>` must be supported for U.
     *
     * The implementation leaves binary compatibility (endianness, IEEE 754 for
     * floats, ...) of the types it serializes in the hands of the `Serializer`
     * function object if compatibility is required.
     */
    template <class Serializer> void serialize(Serializer &serializer) const
    {
      m_ht.serialize(serializer);
    }
 
    /**
     * Deserialize a previously serialized map through the `deserializer`
     * parameter.
     *
     * The `deserializer` parameter must be a function object that supports the
     * following call:
     *  - `template<typename U> U operator()();` where the types `std::int16_t`,
     * `std::uint32_t`, `std::uint64_t`, `float` and `std::pair<Key, T>` must be
     * supported for U.
     *
     * If the deserialized hash map type is hash compatible with the serialized
     * map, the deserialization process can be sped up by setting
     * `hash_compatible` to true. To be hash compatible, the Hash, KeyEqual and
     * GrowthPolicy must behave the same way than the ones used on the serialized
     * map and the StoreHash must have the same value. The `std::size_t` must also
     * be of the same size as the one on the platform used to serialize the map.
     * If these criteria are not met, the behaviour is undefined with
     * `hash_compatible` sets to true.
     *
     * The behaviour is undefined if the type `Key` and `T` of the `robin_map` are
     * not the same as the types used during serialization.
     *
     * The implementation leaves binary compatibility (endianness, IEEE 754 for
     * floats, size of int, ...) of the types it deserializes in the hands of the
     * `Deserializer` function object if compatibility is required.
     */
    template <class Deserializer>
    static robin_map deserialize(Deserializer &deserializer, bool hash_compatible = false)
    {
      robin_map map(0);
      map.m_ht.deserialize(deserializer, hash_compatible);
 
      return map;
    }
 
    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