BAN: Implement basic HashSet
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Bananymous
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#pragma once
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#include <BAN/Errors.h>
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#include <BAN/Hash.h>
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#include <BAN/Math.h>
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#include <BAN/Move.h>
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#include <BAN/Vector.h>
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namespace BAN
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{
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template<typename T, typename HASH>
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class HashSetIterator;
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template<typename T, typename HASH = hash<T>>
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class HashSet
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{
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public:
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using value_type = T;
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using size_type = hash_t;
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using const_iterator = HashSetIterator<T, HASH>;
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public:
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HashSet() = default;
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HashSet(const HashSet<T, HASH>&);
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HashSet(HashSet<T, HASH>&&);
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HashSet<T, HASH>& operator=(const HashSet<T, HASH>&);
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HashSet<T, HASH>& operator=(HashSet<T, HASH>&&);
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[[nodiscard]] ErrorOr<void> insert(const T&);
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[[nodiscard]] ErrorOr<void> insert(T&&);
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void remove(const T&);
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void clear();
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const_iterator begin() const { return const_iterator(this, m_buckets.begin()); }
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const_iterator end() const { return const_iterator(this, m_buckets.end()); }
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bool contains(const T&) const;
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size_type size() const;
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bool empty() const;
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private:
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[[nodiscard]] ErrorOr<void> rebucket(size_type);
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Vector<T>& get_bucket(const T&);
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const Vector<T>& get_bucket(const T&) const;
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private:
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Vector<Vector<T>> m_buckets;
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size_type m_size = 0;
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friend class HashSetIterator<T, HASH>;
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};
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template<typename T, typename HASH>
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class HashSetIterator
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{
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public:
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HashSetIterator() = default;
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HashSetIterator(const HashSetIterator<T, HASH>&);
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HashSetIterator<T, HASH>& operator++();
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HashSetIterator<T, HASH> operator++(int);
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const T& operator*() const;
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const T* operator->() const;
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bool operator==(const HashSetIterator<T, HASH>&) const;
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bool operator!=(const HashSetIterator<T, HASH>&) const;
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operator bool() const { return m_owner && m_current_bucket; }
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private:
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HashSetIterator(const HashSet<T, HASH>* owner, Vector<Vector<T>>::const_iterator bucket);
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void find_next();
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private:
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const HashSet<T, HASH>* m_owner = nullptr;
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Vector<Vector<T>>::const_iterator m_current_bucket;
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Vector<T>::const_iterator m_current_key;
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friend class HashSet<T, HASH>;
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};
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template<typename T, typename HASH>
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HashSet<T, HASH>::HashSet(const HashSet<T, HASH>& other)
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: m_buckets(other.m_buckets)
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, m_size(other.m_size)
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{
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}
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template<typename T, typename HASH>
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HashSet<T, HASH>::HashSet(HashSet<T, HASH>&& other)
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: m_buckets(move(other.m_buckets))
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, m_size(other.m_size)
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{
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other.clear();
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}
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template<typename T, typename HASH>
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HashSet<T, HASH>& HashSet<T, HASH>::operator=(const HashSet<T, HASH>& other)
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{
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clear();
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m_buckets = other.m_buckets;
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m_size = other.m_size;
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return *this;
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}
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template<typename T, typename HASH>
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HashSet<T, HASH>& HashSet<T, HASH>::operator=(HashSet<T, HASH>&& other)
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{
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clear();
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m_buckets = move(other.m_buckets);
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m_size = other.m_size;
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other.clear();
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return *this;
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}
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template<typename T, typename HASH>
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ErrorOr<void> HashSet<T, HASH>::insert(const T& key)
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{
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return insert(move(T(key)));
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}
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template<typename T, typename HASH>
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ErrorOr<void> HashSet<T, HASH>::insert(T&& key)
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{
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if (!empty() && get_bucket(key).contains(key))
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return {};
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TRY(rebucket(m_size + 1));
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TRY(get_bucket(key).push_back(move(key)));
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m_size++;
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return {};
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}
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template<typename T, typename HASH>
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void HashSet<T, HASH>::remove(const T& key)
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{
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if (empty()) return;
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Vector<T>& bucket = get_bucket(key);
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for (size_type i = 0; i < bucket.size(); i++)
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{
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if (bucket[i] == key)
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{
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bucket.remove(i);
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m_size--;
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break;
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}
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}
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}
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template<typename T, typename HASH>
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void HashSet<T, HASH>::clear()
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{
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m_buckets.clear();
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m_size = 0;
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}
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template<typename T, typename HASH>
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bool HashSet<T, HASH>::contains(const T& key) const
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{
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if (empty()) return false;
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return get_bucket(key).contains(key);
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}
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template<typename T, typename HASH>
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typename HashSet<T, HASH>::size_type HashSet<T, HASH>::size() const
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{
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return m_size;
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}
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template<typename T, typename HASH>
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bool HashSet<T, HASH>::empty() const
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{
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return m_size == 0;
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}
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template<typename T, typename HASH>
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ErrorOr<void> HashSet<T, HASH>::rebucket(size_type bucket_count)
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{
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if (m_buckets.size() >= bucket_count)
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return {};
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size_type new_bucket_count = BAN::Math::max<size_type>(bucket_count, m_buckets.size() * 3 / 2);
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Vector<Vector<T>> new_buckets;
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if (new_buckets.resize(new_bucket_count).is_error())
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return Error::from_string("HashSet: Could not allocate memory");
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// NOTE: We have to copy the old keys to the new keys and not move
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// since we might run out of memory half way through.
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for (Vector<T>& bucket : m_buckets)
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{
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for (T& key : bucket)
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{
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size_type bucket_index = HASH()(key) % new_buckets.size();
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if (new_buckets[bucket_index].push_back(key).is_error())
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return Error::from_string("HashSet: Could not allocate memory");
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}
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}
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m_buckets = move(new_buckets);
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return {};
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}
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template<typename T, typename HASH>
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Vector<T>& HashSet<T, HASH>::get_bucket(const T& key)
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{
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ASSERT(!m_buckets.empty());
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size_type index = HASH()(key) % m_buckets.size();
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return m_buckets[index];
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}
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template<typename T, typename HASH>
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const Vector<T>& HashSet<T, HASH>::get_bucket(const T& key) const
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{
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ASSERT(!m_buckets.empty());
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size_type index = HASH()(key) % m_buckets.size();
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return m_buckets[index];
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}
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template<typename T, typename HASH>
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HashSetIterator<T, HASH>& HashSetIterator<T, HASH>::operator++()
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{
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ASSERT(*this);
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if (m_current_key == m_current_bucket->end())
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m_current_bucket++;
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else
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m_current_key++;
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find_next();
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return *this;
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}
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template<typename T, typename HASH>
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HashSetIterator<T, HASH> HashSetIterator<T, HASH>::operator++(int)
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{
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auto temp = *this;
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++(*this);
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return temp;
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}
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template<typename T, typename HASH>
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const T& HashSetIterator<T, HASH>::operator*() const
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{
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ASSERT(m_owner && m_current_bucket && m_current_key);
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return *m_current_key;
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}
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template<typename T, typename HASH>
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const T* HashSetIterator<T, HASH>::operator->() const
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{
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return &**this;
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}
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template<typename T, typename HASH>
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bool HashSetIterator<T, HASH>::operator==(const HashSetIterator<T, HASH>& other) const
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{
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if (!m_owner || m_owner != other.m_owner)
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return false;
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return m_current_bucket == other.m_current_bucket
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&& m_current_key == other.m_current_key;
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}
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template<typename T, typename HASH>
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bool HashSetIterator<T, HASH>::operator!=(const HashSetIterator<T, HASH>& other) const
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{
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return !(*this == other);
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}
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template<typename T, typename HASH>
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HashSetIterator<T, HASH>::HashSetIterator(const HashSet<T, HASH>* owner, Vector<Vector<T>>::const_iterator bucket)
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: m_owner(owner)
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, m_current_bucket(bucket)
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{
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if (m_current_bucket != m_owner->m_buckets.end())
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m_current_key = m_current_bucket->begin();
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find_next();
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}
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template<typename T, typename HASH>
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void HashSetIterator<T, HASH>::find_next()
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{
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ASSERT(m_owner && m_current_bucket);
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while (m_current_bucket != m_owner->m_buckets.end())
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{
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if (m_current_key && m_current_key != m_current_bucket->end())
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return;
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m_current_bucket++;
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m_current_key = m_current_bucket->begin();
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}
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m_current_key = typename Vector<T>::const_iterator();
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}
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}
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