Cppcheck report - Godot - branch: master, commit: 216b3302f318c32a5dcf250293d90e47e712e8e9 (2024-12-22): core/templates/hash_map.h

/**************************************************************************/
/*  hash_map.h                                                            */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#ifndef HASH_MAP_H
#define HASH_MAP_H

#include "core/os/memory.h"
#include "core/templates/hashfuncs.h"
#include "core/templates/pair.h"

#include <initializer_list>

/**
 * A HashMap implementation that uses open addressing with Robin Hood hashing.
 * Robin Hood hashing swaps out entries that have a smaller probing distance
 * than the to-be-inserted entry, that evens out the average probing distance
 * and enables faster lookups. Backward shift deletion is employed to further
 * improve the performance and to avoid infinite loops in rare cases.
 *
 * Keys and values are stored in a double linked list by insertion order. This
 * has a slight performance overhead on lookup, which can be mostly compensated
 * using a paged allocator if required.
 *
 * The assignment operator copy the pairs from one map to the other.
 */

template <typename TKey, typename TValue>
struct HashMapElement {
	HashMapElement *next = nullptr;
	HashMapElement *prev = nullptr;
	KeyValue<TKey, TValue> data;
	HashMapElement() {}
	HashMapElement(const TKey &p_key, const TValue &p_value) :
			data(p_key, p_value) {}
};

bool _hashmap_variant_less_than(const Variant &p_left, const Variant &p_right);

template <typename TKey, typename TValue,
		typename Hasher = HashMapHasherDefault,
		typename Comparator = HashMapComparatorDefault<TKey>,
		typename Allocator = DefaultTypedAllocator<HashMapElement<TKey, TValue>>>
class HashMap {
public:
	static constexpr uint32_t MIN_CAPACITY_INDEX = 2; // Use a prime.
	static constexpr float MAX_OCCUPANCY = 0.75;
	static constexpr uint32_t EMPTY_HASH = 0;

private:
	Allocator element_alloc;
	HashMapElement<TKey, TValue> **elements = nullptr;
	uint32_t *hashes = nullptr;
	HashMapElement<TKey, TValue> *head_element = nullptr;
	HashMapElement<TKey, TValue> *tail_element = nullptr;

	uint32_t capacity_index = 0;
	uint32_t num_elements = 0;

	_FORCE_INLINE_ uint32_t _hash(const TKey &p_key) const {
		uint32_t hash = Hasher::hash(p_key);

		if (unlikely(hash == EMPTY_HASH)) {
			hash = EMPTY_HASH + 1;
		}

		return hash;
	}

	static _FORCE_INLINE_ uint32_t _get_probe_length(const uint32_t p_pos, const uint32_t p_hash, const uint32_t p_capacity, const uint64_t p_capacity_inv) {
		const uint32_t original_pos = fastmod(p_hash, p_capacity_inv, p_capacity);
		return fastmod(p_pos - original_pos + p_capacity, p_capacity_inv, p_capacity);
	}

	bool _lookup_pos(const TKey &p_key, uint32_t &r_pos) const {
		if (elements == nullptr || num_elements == 0) {
			return false; // Failed lookups, no elements
		}

		const uint32_t capacity = hash_table_size_primes[capacity_index];
		const uint64_t capacity_inv = hash_table_size_primes_inv[capacity_index];
		uint32_t hash = _hash(p_key);
		uint32_t pos = fastmod(hash, capacity_inv, capacity);
		uint32_t distance = 0;

		while (true) {
			if (hashes[pos] == EMPTY_HASH) {
				return false;
			}

			if (distance > _get_probe_length(pos, hashes[pos], capacity, capacity_inv)) {
				return false;
			}

			if (hashes[pos] == hash && Comparator::compare(elements[pos]->data.key, p_key)) {
				r_pos = pos;
				return true;
			}

			pos = fastmod((pos + 1), capacity_inv, capacity);
			distance++;
		}
	}

	void _insert_with_hash(uint32_t p_hash, HashMapElement<TKey, TValue> *p_value) {
		const uint32_t capacity = hash_table_size_primes[capacity_index];
		const uint64_t capacity_inv = hash_table_size_primes_inv[capacity_index];
		uint32_t hash = p_hash;
		HashMapElement<TKey, TValue> *value = p_value;
		uint32_t distance = 0;
		uint32_t pos = fastmod(hash, capacity_inv, capacity);

		while (true) {
			if (hashes[pos] == EMPTY_HASH) {
				elements[pos] = value;
				hashes[pos] = hash;

				num_elements++;

				return;
			}

			// Not an empty slot, let's check the probing length of the existing one.
			uint32_t existing_probe_len = _get_probe_length(pos, hashes[pos], capacity, capacity_inv);
			if (existing_probe_len < distance) {
				SWAP(hash, hashes[pos]);
				SWAP(value, elements[pos]);
				distance = existing_probe_len;
			}

			pos = fastmod((pos + 1), capacity_inv, capacity);
			distance++;
		}
	}

	void _resize_and_rehash(uint32_t p_new_capacity_index) {
		uint32_t old_capacity = hash_table_size_primes[capacity_index];

		// Capacity can't be 0.
		capacity_index = MAX((uint32_t)MIN_CAPACITY_INDEX, p_new_capacity_index);

		uint32_t capacity = hash_table_size_primes[capacity_index];

		HashMapElement<TKey, TValue> **old_elements = elements;
		uint32_t *old_hashes = hashes;

		num_elements = 0;
		hashes = reinterpret_cast<uint32_t *>(Memory::alloc_static(sizeof(uint32_t) * capacity));
		elements = reinterpret_cast<HashMapElement<TKey, TValue> **>(Memory::alloc_static(sizeof(HashMapElement<TKey, TValue> *) * capacity));

		for (uint32_t i = 0; i < capacity; i++) {
			hashes[i] = 0;
			elements[i] = nullptr;
		}

		if (old_capacity == 0) {
			// Nothing to do.
			return;
		}

		for (uint32_t i = 0; i < old_capacity; i++) {
			if (old_hashes[i] == EMPTY_HASH) {
				continue;
			}

			_insert_with_hash(old_hashes[i], old_elements[i]);
		}

		Memory::free_static(old_elements);
		Memory::free_static(old_hashes);
	}

	_FORCE_INLINE_ HashMapElement<TKey, TValue> *_insert(const TKey &p_key, const TValue &p_value, bool p_front_insert = false) {
		uint32_t capacity = hash_table_size_primes[capacity_index];
		if (unlikely(elements == nullptr)) {
			// Allocate on demand to save memory.

			hashes = reinterpret_cast<uint32_t *>(Memory::alloc_static(sizeof(uint32_t) * capacity));
			elements = reinterpret_cast<HashMapElement<TKey, TValue> **>(Memory::alloc_static(sizeof(HashMapElement<TKey, TValue> *) * capacity));

			for (uint32_t i = 0; i < capacity; i++) {
				hashes[i] = EMPTY_HASH;
				elements[i] = nullptr;
			}
		}

		uint32_t pos = 0;
		bool exists = _lookup_pos(p_key, pos);

		if (exists) {
			elements[pos]->data.value = p_value;
			return elements[pos];
		} else {
			if (num_elements + 1 > MAX_OCCUPANCY * capacity) {
				ERR_FAIL_COND_V_MSG(capacity_index + 1 == HASH_TABLE_SIZE_MAX, nullptr, "Hash table maximum capacity reached, aborting insertion.");
				_resize_and_rehash(capacity_index + 1);
			}

			HashMapElement<TKey, TValue> *elem = element_alloc.new_allocation(HashMapElement<TKey, TValue>(p_key, p_value));

			if (tail_element == nullptr) {
				head_element = elem;
				tail_element = elem;
			} else if (p_front_insert) {
				head_element->prev = elem;
				elem->next = head_element;
				head_element = elem;
			} else {
				tail_element->next = elem;
				elem->prev = tail_element;
				tail_element = elem;
			}

			uint32_t hash = _hash(p_key);
			_insert_with_hash(hash, elem);
			return elem;
		}
	}

public:
	_FORCE_INLINE_ uint32_t get_capacity() const { return hash_table_size_primes[capacity_index]; }
	_FORCE_INLINE_ uint32_t size() const { return num_elements; }

	/* Standard Godot Container API */

	bool is_empty() const {
		return num_elements == 0;
	}

	void clear() {
		if (elements == nullptr || num_elements == 0) {
			return;
		}
		uint32_t capacity = hash_table_size_primes[capacity_index];
		for (uint32_t i = 0; i < capacity; i++) {
			if (hashes[i] == EMPTY_HASH) {
				continue;
			}

			hashes[i] = EMPTY_HASH;
			element_alloc.delete_allocation(elements[i]);
			elements[i] = nullptr;
		}

		tail_element = nullptr;
		head_element = nullptr;
		num_elements = 0;
	}

	void sort() {
		if (elements == nullptr || num_elements < 2) {
			return; // An empty or single element HashMap is already sorted.
		}
		// Use insertion sort because we want this operation to be fast for the
		// common case where the input is already sorted or nearly sorted.
		HashMapElement<TKey, TValue> *inserting = head_element->next;
		while (inserting != nullptr) {
			HashMapElement<TKey, TValue> *after = nullptr;
			for (HashMapElement<TKey, TValue> *current = inserting->prev; current != nullptr; current = current->prev) {
				if (_hashmap_variant_less_than(inserting->data.key, current->data.key)) {
					after = current;
				} else {
					break;
				}
			}
			HashMapElement<TKey, TValue> *next = inserting->next;
			if (after != nullptr) {
				// Modify the elements around `inserting` to remove it from its current position.
				inserting->prev->next = next;
				if (next == nullptr) {
					tail_element = inserting->prev;
				} else {
					next->prev = inserting->prev;
				}
				// Modify `before` and `after` to insert `inserting` between them.
				HashMapElement<TKey, TValue> *before = after->prev;
				if (before == nullptr) {
					head_element = inserting;
				} else {
					before->next = inserting;
				}
				after->prev = inserting;
				// Point `inserting` to its new surroundings.
				inserting->prev = before;
				inserting->next = after;
			}
			inserting = next;
		}
	}

	TValue &get(const TKey &p_key) {
		uint32_t pos = 0;
		bool exists = _lookup_pos(p_key, pos);
		CRASH_COND_MSG(!exists, "HashMap key not found.");
		return elements[pos]->data.value;
	}

	const TValue &get(const TKey &p_key) const {
		uint32_t pos = 0;
		bool exists = _lookup_pos(p_key, pos);
		CRASH_COND_MSG(!exists, "HashMap key not found.");
		return elements[pos]->data.value;
	}

	const TValue *getptr(const TKey &p_key) const {
		uint32_t pos = 0;
		bool exists = _lookup_pos(p_key, pos);

		if (exists) {
			return &elements[pos]->data.value;
		}
		return nullptr;
	}

	TValue *getptr(const TKey &p_key) {
		uint32_t pos = 0;
		bool exists = _lookup_pos(p_key, pos);

		if (exists) {
			return &elements[pos]->data.value;
		}
		return nullptr;
	}

	_FORCE_INLINE_ bool has(const TKey &p_key) const {
		uint32_t _pos = 0;
		return _lookup_pos(p_key, _pos);
	}

	bool erase(const TKey &p_key) {
		uint32_t pos = 0;
		bool exists = _lookup_pos(p_key, pos);

		if (!exists) {
			return false;
		}

		const uint32_t capacity = hash_table_size_primes[capacity_index];
		const uint64_t capacity_inv = hash_table_size_primes_inv[capacity_index];
		uint32_t next_pos = fastmod((pos + 1), capacity_inv, capacity);
		while (hashes[next_pos] != EMPTY_HASH && _get_probe_length(next_pos, hashes[next_pos], capacity, capacity_inv) != 0) {
			SWAP(hashes[next_pos], hashes[pos]);
			SWAP(elements[next_pos], elements[pos]);
			pos = next_pos;
			next_pos = fastmod((pos + 1), capacity_inv, capacity);
		}

		hashes[pos] = EMPTY_HASH;

		if (head_element == elements[pos]) {
			head_element = elements[pos]->next;
		}

		if (tail_element == elements[pos]) {
			tail_element = elements[pos]->prev;
		}

		if (elements[pos]->prev) {
			elements[pos]->prev->next = elements[pos]->next;
		}

		if (elements[pos]->next) {
			elements[pos]->next->prev = elements[pos]->prev;
		}

		element_alloc.delete_allocation(elements[pos]);
		elements[pos] = nullptr;

		num_elements--;
		return true;
	}

	// Replace the key of an entry in-place, without invalidating iterators or changing the entries position during iteration.
	// p_old_key must exist in the map and p_new_key must not, unless it is equal to p_old_key.
	bool replace_key(const TKey &p_old_key, const TKey &p_new_key) {
		if (p_old_key == p_new_key) {
			return true;
		}
		uint32_t pos = 0;
		ERR_FAIL_COND_V(_lookup_pos(p_new_key, pos), false);
		ERR_FAIL_COND_V(!_lookup_pos(p_old_key, pos), false);
		HashMapElement<TKey, TValue> *element = elements[pos];

		// Delete the old entries in hashes and elements.
		const uint32_t capacity = hash_table_size_primes[capacity_index];
		const uint64_t capacity_inv = hash_table_size_primes_inv[capacity_index];
		uint32_t next_pos = fastmod((pos + 1), capacity_inv, capacity);
		while (hashes[next_pos] != EMPTY_HASH && _get_probe_length(next_pos, hashes[next_pos], capacity, capacity_inv) != 0) {
			SWAP(hashes[next_pos], hashes[pos]);
			SWAP(elements[next_pos], elements[pos]);
			pos = next_pos;
			next_pos = fastmod((pos + 1), capacity_inv, capacity);
		}
		hashes[pos] = EMPTY_HASH;
		elements[pos] = nullptr;
		// _insert_with_hash will increment this again.
		num_elements--;

		// Update the HashMapElement with the new key and reinsert it.
		const_cast<TKey &>(element->data.key) = p_new_key;
		uint32_t hash = _hash(p_new_key);
		_insert_with_hash(hash, element);

		return true;
	}

	// Reserves space for a number of elements, useful to avoid many resizes and rehashes.
	// If adding a known (possibly large) number of elements at once, must be larger than old capacity.
	void reserve(uint32_t p_new_capacity) {
		uint32_t new_index = capacity_index;

		while (hash_table_size_primes[new_index] < p_new_capacity) {
			ERR_FAIL_COND_MSG(new_index + 1 == (uint32_t)HASH_TABLE_SIZE_MAX, nullptr);
			new_index++;
		}

		if (new_index == capacity_index) {
			return;
		}

		if (elements == nullptr) {
			capacity_index = new_index;
			return; // Unallocated yet.
		}
		_resize_and_rehash(new_index);
	}

	/** Iterator API **/

	struct ConstIterator {
		_FORCE_INLINE_ const KeyValue<TKey, TValue> &operator*() const {
			return E->data;
		}
		_FORCE_INLINE_ const KeyValue<TKey, TValue> *operator->() const { return &E->data; }
		_FORCE_INLINE_ ConstIterator &operator++() {
			if (E) {
				E = E->next;
			}
			return *this;
		}
		_FORCE_INLINE_ ConstIterator &operator--() {
			if (E) {
				E = E->prev;
			}
			return *this;
		}

		_FORCE_INLINE_ bool operator==(const ConstIterator &b) const { return E == b.E; }
		_FORCE_INLINE_ bool operator!=(const ConstIterator &b) const { return E != b.E; }

		_FORCE_INLINE_ explicit operator bool() const {
			return E != nullptr;
		}

		_FORCE_INLINE_ ConstIterator(const HashMapElement<TKey, TValue> *p_E) { E = p_E; }
<--- Struct 'ConstIterator' has a constructor with 1 argument that is not explicit. [+]
Struct 'ConstIterator' has a constructor with 1 argument that is not explicit. Such constructors should in general be explicit for type safety reasons. Using the explicit keyword in the constructor means some mistakes when using the class can be avoided.
		_FORCE_INLINE_ ConstIterator() {}
		_FORCE_INLINE_ ConstIterator(const ConstIterator &p_it) { E = p_it.E; }
		_FORCE_INLINE_ void operator=(const ConstIterator &p_it) {
			E = p_it.E;
		}

	private:
		const HashMapElement<TKey, TValue> *E = nullptr;
	};

	struct Iterator {
		_FORCE_INLINE_ KeyValue<TKey, TValue> &operator*() const {
			return E->data;
		}
		_FORCE_INLINE_ KeyValue<TKey, TValue> *operator->() const { return &E->data; }
		_FORCE_INLINE_ Iterator &operator++() {
			if (E) {
				E = E->next;
			}
			return *this;
		}
		_FORCE_INLINE_ Iterator &operator--() {
			if (E) {
				E = E->prev;
			}
			return *this;
		}

		_FORCE_INLINE_ bool operator==(const Iterator &b) const { return E == b.E; }
		_FORCE_INLINE_ bool operator!=(const Iterator &b) const { return E != b.E; }

		_FORCE_INLINE_ explicit operator bool() const {
			return E != nullptr;
		}

		_FORCE_INLINE_ Iterator(HashMapElement<TKey, TValue> *p_E) { E = p_E; }
<--- Struct 'Iterator' has a constructor with 1 argument that is not explicit. [+]
Struct 'Iterator' has a constructor with 1 argument that is not explicit. Such constructors should in general be explicit for type safety reasons. Using the explicit keyword in the constructor means some mistakes when using the class can be avoided.
		_FORCE_INLINE_ Iterator() {}
		_FORCE_INLINE_ Iterator(const Iterator &p_it) { E = p_it.E; }
		_FORCE_INLINE_ void operator=(const Iterator &p_it) {
			E = p_it.E;
		}

		operator ConstIterator() const {
			return ConstIterator(E);
		}

	private:
		HashMapElement<TKey, TValue> *E = nullptr;
	};

	_FORCE_INLINE_ Iterator begin() {
		return Iterator(head_element);
	}
	_FORCE_INLINE_ Iterator end() {
		return Iterator(nullptr);
	}
	_FORCE_INLINE_ Iterator last() {
		return Iterator(tail_element);
	}

	_FORCE_INLINE_ Iterator find(const TKey &p_key) {
		uint32_t pos = 0;
		bool exists = _lookup_pos(p_key, pos);
		if (!exists) {
			return end();
		}
		return Iterator(elements[pos]);
	}

	_FORCE_INLINE_ void remove(const Iterator &p_iter) {
		if (p_iter) {
			erase(p_iter->key);
		}
	}

	_FORCE_INLINE_ ConstIterator begin() const {
		return ConstIterator(head_element);
	}
	_FORCE_INLINE_ ConstIterator end() const {
		return ConstIterator(nullptr);
	}
	_FORCE_INLINE_ ConstIterator last() const {
		return ConstIterator(tail_element);
	}

	_FORCE_INLINE_ ConstIterator find(const TKey &p_key) const {
		uint32_t pos = 0;
		bool exists = _lookup_pos(p_key, pos);
		if (!exists) {
			return end();
		}
		return ConstIterator(elements[pos]);
	}

	/* Indexing */

	const TValue &operator[](const TKey &p_key) const {
		uint32_t pos = 0;
		bool exists = _lookup_pos(p_key, pos);
		CRASH_COND(!exists);
		return elements[pos]->data.value;
	}

	TValue &operator[](const TKey &p_key) {
		uint32_t pos = 0;
		bool exists = _lookup_pos(p_key, pos);
		if (!exists) {
			return _insert(p_key, TValue())->data.value;
		} else {
			return elements[pos]->data.value;
		}
	}

	/* Insert */

	Iterator insert(const TKey &p_key, const TValue &p_value, bool p_front_insert = false) {
		return Iterator(_insert(p_key, p_value, p_front_insert));
	}

	/* Constructors */

	HashMap(const HashMap &p_other) {
		reserve(hash_table_size_primes[p_other.capacity_index]);

		if (p_other.num_elements == 0) {
			return;
		}

		for (const KeyValue<TKey, TValue> &E : p_other) {
			insert(E.key, E.value);
		}
	}

	void operator=(const HashMap &p_other) {
		if (this == &p_other) {
			return; // Ignore self assignment.
		}
		if (num_elements != 0) {
			clear();
		}

		reserve(hash_table_size_primes[p_other.capacity_index]);

		if (p_other.elements == nullptr) {
			return; // Nothing to copy.
		}

		for (const KeyValue<TKey, TValue> &E : p_other) {
			insert(E.key, E.value);
		}
	}

	HashMap(uint32_t p_initial_capacity) {
<--- Class 'HashMap' has a constructor with 1 argument that is not explicit. [+]
Class 'HashMap' has a constructor with 1 argument that is not explicit. Such constructors should in general be explicit for type safety reasons. Using the explicit keyword in the constructor means some mistakes when using the class can be avoided.
		// Capacity can't be 0.
		capacity_index = 0;
		reserve(p_initial_capacity);
	}
	HashMap() {
		capacity_index = MIN_CAPACITY_INDEX;
	}

	HashMap(std::initializer_list<KeyValue<TKey, TValue>> p_init) {
<--- Class 'HashMap' has a constructor with 1 argument that is not explicit. [+]
Class 'HashMap' has a constructor with 1 argument that is not explicit. Such constructors should in general be explicit for type safety reasons. Using the explicit keyword in the constructor means some mistakes when using the class can be avoided.
		reserve(p_init.size());
		for (const KeyValue<TKey, TValue> &E : p_init) {
			insert(E.key, E.value);
		}
	}

	uint32_t debug_get_hash(uint32_t p_index) {
		if (num_elements == 0) {
			return 0;
		}
		ERR_FAIL_INDEX_V(p_index, get_capacity(), 0);
		return hashes[p_index];
	}
	Iterator debug_get_element(uint32_t p_index) {
		if (num_elements == 0) {
			return Iterator();
		}
		ERR_FAIL_INDEX_V(p_index, get_capacity(), Iterator());
		return Iterator(elements[p_index]);
	}

	~HashMap() {
		clear();

		if (elements != nullptr) {
			Memory::free_static(elements);
			Memory::free_static(hashes);
		}
	}
};

#endif // HASH_MAP_H