robin_set.h

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/**
 * MIT License
 *
 * Copyright (c) 2017 Tessil
 *
 * 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_SET_H
#define TSL_ROBIN_SET_H

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

namespace tsl {

  /**
   * Implementation of a hash set using open-adressing and the robin hood hashing algorithm with
   * backward shift deletion.
   *
   * For operations modifying the hash set (insert, erase, rehash, ...), the strong exception
   * guarantee is only guaranteed when the expression `std::is_nothrow_swappable<Key>\:\:value &&
   * std::is_nothrow_move_constructible<Key>\:\:value` is true, otherwise if an exception
   * is thrown during the swap or the move, the hash set may end up in a undefined state. Per the
   * standard a `Key` with a noexcept copy constructor and no move constructor also satisfies the
   * `std::is_nothrow_move_constructible<Key>\:\:value` criterion (and will thus guarantee the
   * strong exception for the set).
   *
   * 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 (or 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 penality due to alignement (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 set grows and consequently how a hash value is mapped to a
   * bucket. By default the set 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 set 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.
   *
   * If the destructor of `Key` 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 Hash = std::hash<Key>, class KeyEqual = std::equal_to<Key>,
            class Allocator = std::allocator<Key>, bool StoreHash = false,
            class GrowthPolicy = tsl::rh::power_of_two_growth_policy<2>>
  class robin_set
  {
  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 Key &key) const noexcept { return key; }

      key_type &operator()(Key &key) noexcept { return key; }
    };

    using ht = detail_robin_hash::robin_hash<Key, KeySelect, void, Hash, KeyEqual, Allocator,
                                             StoreHash, GrowthPolicy>;

  public:
    using key_type        = typename ht::key_type;
    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;

    /*
     * Constructors
     */
    robin_set() : robin_set(ht::DEFAULT_INIT_BUCKETS_SIZE) {}

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

    robin_set(size_type my_bucket_count, const Allocator &alloc)
        : robin_set(my_bucket_count, Hash(), KeyEqual(), alloc)
    {
    }

    robin_set(size_type my_bucket_count, const Hash &hash, const Allocator &alloc)
        : robin_set(my_bucket_count, hash, KeyEqual(), alloc)
    {
    }

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

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

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

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

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

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

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

    robin_set &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); }

    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);
    }

    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());
    }

    /**
     * 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)...);
    }

    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). Usefull 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). Usefull 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_set &other) { other.m_ht.swap(m_ht); }

    /*
     * Lookup
     */
    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). Usefull 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). Usefull 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). Usefull 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). Usefull 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). Usefull 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);
    }

    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). Usefull 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). Usefull 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 set goes
     * below `min_load_factor` after some erase operations, the set will be
     * shrunk when an insertion occurs. The erase method itself never shrinks
     * the set.
     *
     * The default value of `min_load_factor` is 0.0f, the set 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); }

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

      for (const auto &element_lhs : lhs) {
        const auto it_element_rhs = rhs.find(element_lhs);
        if (it_element_rhs == rhs.cend()) {
          return false;
        }
      }

      return true;
    }

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

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

  private:
    ht m_ht;
  };

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

} // end namespace tsl

#endif