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godot/core/templates/hash_map.h

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/*************************************************************************/
/* hash_map.h */
/*************************************************************************/
/* This file is part of: */
/* GODOT ENGINE */
/* https://godotengine.org */
/*************************************************************************/
/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur. */
/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md). */
/* */
/* 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 HASH_MAP_H
#define HASH_MAP_H
#include "core/math/math_funcs.h"
#include "core/os/memory.h"
#include "core/templates/hashfuncs.h"
#include "core/templates/paged_allocator.h"
#include "core/templates/pair.h"
/**
* 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 <class TKey, class 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) {}
};
template <class TKey, class TValue,
class Hasher = HashMapHasherDefault,
class Comparator = HashMapComparatorDefault<TKey>,
class Allocator = DefaultTypedAllocator<HashMapElement<TKey, TValue>>>
class HashMap {
public:
const uint32_t MIN_CAPACITY_INDEX = 2; // Use a prime.
const float MAX_OCCUPANCY = 0.75;
const 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;
}
_FORCE_INLINE_ uint32_t _get_probe_length(uint32_t p_pos, uint32_t p_hash, uint32_t p_capacity) const {
uint32_t original_pos = p_hash % p_capacity;
return (p_pos - original_pos + p_capacity) % p_capacity;
}
bool _lookup_pos(const TKey &p_key, uint32_t &r_pos) const {
if (elements == nullptr) {
return false; // Failed lookups, no elements
}
uint32_t capacity = hash_table_size_primes[capacity_index];
uint32_t hash = _hash(p_key);
uint32_t pos = hash % capacity;
uint32_t distance = 0;
while (true) {
if (hashes[pos] == EMPTY_HASH) {
return false;
}
if (distance > _get_probe_length(pos, hashes[pos], capacity)) {
return false;
}
if (hashes[pos] == hash && Comparator::compare(elements[pos]->data.key, p_key)) {
r_pos = pos;
return true;
}
pos = (pos + 1) % capacity;
distance++;
}
}
void _insert_with_hash(uint32_t p_hash, HashMapElement<TKey, TValue> *p_value) {
uint32_t capacity = hash_table_size_primes[capacity_index];
uint32_t hash = p_hash;
HashMapElement<TKey, TValue> *value = p_value;
uint32_t distance = 0;
uint32_t pos = hash % 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);
if (existing_probe_len < distance) {
SWAP(hash, hashes[pos]);
SWAP(value, elements[pos]);
distance = existing_probe_len;
}
pos = (pos + 1) % 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) {
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;
}
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;
}
uint32_t capacity = hash_table_size_primes[capacity_index];
uint32_t next_pos = (pos + 1) % capacity;
while (hashes[next_pos] != EMPTY_HASH && _get_probe_length(next_pos, hashes[next_pos], capacity) != 0) {
SWAP(hashes[next_pos], hashes[pos]);
SWAP(elements[next_pos], elements[pos]);
pos = next_pos;
next_pos = (pos + 1) % 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;
}
// 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; }
_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; }
_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) {
// Capacity can't be 0.
capacity_index = 0;
reserve(p_initial_capacity);
}
HashMap() {
capacity_index = MIN_CAPACITY_INDEX;
}
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
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