360 lines
9.5 KiB
C++
360 lines
9.5 KiB
C++
/*************************************************************************/
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/* oa_hash_map.h */
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/*************************************************************************/
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/* This file is part of: */
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/* GODOT ENGINE */
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/* https://godotengine.org */
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/*************************************************************************/
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/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur. */
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/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md). */
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/* */
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/* Permission is hereby granted, free of charge, to any person obtaining */
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/* a copy of this software and associated documentation files (the */
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/* "Software"), to deal in the Software without restriction, including */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* distribute, sublicense, and/or sell copies of the Software, and to */
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/* permit persons to whom the Software is furnished to do so, subject to */
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/* the following conditions: */
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/* */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/*************************************************************************/
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#ifndef OA_HASH_MAP_H
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#define OA_HASH_MAP_H
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#include "core/hashfuncs.h"
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#include "core/math/math_funcs.h"
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#include "core/os/memory.h"
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/**
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* A HashMap implementation that uses open addressing with Robin Hood hashing.
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* Robin Hood hashing swaps out entries that have a smaller probing distance
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* than the to-be-inserted entry, that evens out the average probing distance
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* and enables faster lookups. Backward shift deletion is employed to further
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* improve the performance and to avoid infinite loops in rare cases.
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*
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* The entries are stored inplace, so huge keys or values might fill cache lines
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* a lot faster.
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*
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* Only used keys and values are constructed. For free positions there's space
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* in the arrays for each, but that memory is kept uninitialized.
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*/
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template <class TKey, class TValue,
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class Hasher = HashMapHasherDefault,
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class Comparator = HashMapComparatorDefault<TKey>>
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class OAHashMap {
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private:
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TValue *values;
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TKey *keys;
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uint32_t *hashes;
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uint32_t capacity;
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uint32_t num_elements;
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static const uint32_t EMPTY_HASH = 0;
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_FORCE_INLINE_ uint32_t _hash(const TKey &p_key) const {
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uint32_t hash = Hasher::hash(p_key);
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if (hash == EMPTY_HASH) {
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hash = EMPTY_HASH + 1;
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}
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return hash;
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}
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_FORCE_INLINE_ uint32_t _get_probe_length(uint32_t p_pos, uint32_t p_hash) const {
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uint32_t original_pos = p_hash % capacity;
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return (p_pos - original_pos + capacity) % capacity;
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}
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_FORCE_INLINE_ void _construct(uint32_t p_pos, uint32_t p_hash, const TKey &p_key, const TValue &p_value) {
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memnew_placement(&keys[p_pos], TKey(p_key));
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memnew_placement(&values[p_pos], TValue(p_value));
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hashes[p_pos] = p_hash;
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num_elements++;
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}
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bool _lookup_pos(const TKey &p_key, uint32_t &r_pos) const {
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uint32_t hash = _hash(p_key);
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uint32_t pos = hash % capacity;
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uint32_t distance = 0;
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while (42) {
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if (hashes[pos] == EMPTY_HASH) {
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return false;
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}
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if (distance > _get_probe_length(pos, hashes[pos])) {
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return false;
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}
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if (hashes[pos] == hash && Comparator::compare(keys[pos], p_key)) {
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r_pos = pos;
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return true;
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}
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pos = (pos + 1) % capacity;
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distance++;
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}
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}
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void _insert_with_hash(uint32_t p_hash, const TKey &p_key, const TValue &p_value) {
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uint32_t hash = p_hash;
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uint32_t distance = 0;
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uint32_t pos = hash % capacity;
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TKey key = p_key;
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TValue value = p_value;
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while (42) {
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if (hashes[pos] == EMPTY_HASH) {
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_construct(pos, hash, key, value);
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return;
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}
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// not an empty slot, let's check the probing length of the existing one
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uint32_t existing_probe_len = _get_probe_length(pos, hashes[pos]);
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if (existing_probe_len < distance) {
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SWAP(hash, hashes[pos]);
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SWAP(key, keys[pos]);
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SWAP(value, values[pos]);
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distance = existing_probe_len;
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}
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pos = (pos + 1) % capacity;
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distance++;
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}
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}
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void _resize_and_rehash(uint32_t p_new_capacity) {
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uint32_t old_capacity = capacity;
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capacity = p_new_capacity;
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TKey *old_keys = keys;
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TValue *old_values = values;
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uint32_t *old_hashes = hashes;
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num_elements = 0;
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keys = static_cast<TKey *>(Memory::alloc_static(sizeof(TKey) * capacity));
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values = static_cast<TValue *>(Memory::alloc_static(sizeof(TValue) * capacity));
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hashes = static_cast<uint32_t *>(Memory::alloc_static(sizeof(uint32_t) * capacity));
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for (uint32_t i = 0; i < capacity; i++) {
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hashes[i] = 0;
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}
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for (uint32_t i = 0; i < old_capacity; i++) {
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if (old_hashes[i] == EMPTY_HASH) {
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continue;
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}
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_insert_with_hash(old_hashes[i], old_keys[i], old_values[i]);
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old_keys[i].~TKey();
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old_values[i].~TValue();
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}
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Memory::free_static(old_keys);
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Memory::free_static(old_values);
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Memory::free_static(old_hashes);
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}
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void _resize_and_rehash() {
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_resize_and_rehash(capacity * 2);
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}
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public:
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_FORCE_INLINE_ uint32_t get_capacity() const { return capacity; }
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_FORCE_INLINE_ uint32_t get_num_elements() const { return num_elements; }
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bool empty() const {
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return num_elements == 0;
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}
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void clear() {
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for (uint32_t i = 0; i < capacity; i++) {
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if (hashes[i] == EMPTY_HASH) {
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continue;
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}
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hashes[i] = EMPTY_HASH;
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values[i].~TValue();
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keys[i].~TKey();
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}
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num_elements = 0;
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}
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void insert(const TKey &p_key, const TValue &p_value) {
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if (num_elements + 1 > 0.9 * capacity) {
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_resize_and_rehash();
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}
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uint32_t hash = _hash(p_key);
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_insert_with_hash(hash, p_key, p_value);
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}
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void set(const TKey &p_key, const TValue &p_data) {
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uint32_t pos = 0;
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bool exists = _lookup_pos(p_key, pos);
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if (exists) {
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values[pos] = p_data;
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} else {
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insert(p_key, p_data);
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}
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}
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/**
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* returns true if the value was found, false otherwise.
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*
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* if r_data is not NULL then the value will be written to the object
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* it points to.
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*/
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bool lookup(const TKey &p_key, TValue &r_data) const {
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uint32_t pos = 0;
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bool exists = _lookup_pos(p_key, pos);
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if (exists) {
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r_data = values[pos];
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return true;
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}
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return false;
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}
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_FORCE_INLINE_ bool has(const TKey &p_key) const {
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uint32_t _pos = 0;
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return _lookup_pos(p_key, _pos);
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}
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void remove(const TKey &p_key) {
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uint32_t pos = 0;
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bool exists = _lookup_pos(p_key, pos);
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if (!exists) {
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return;
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}
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uint32_t next_pos = (pos + 1) % capacity;
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while (hashes[next_pos] != EMPTY_HASH &&
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_get_probe_length(next_pos, hashes[next_pos]) != 0) {
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SWAP(hashes[next_pos], hashes[pos]);
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SWAP(keys[next_pos], keys[pos]);
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SWAP(values[next_pos], values[pos]);
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pos = next_pos;
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next_pos = (pos + 1) % capacity;
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}
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hashes[pos] = EMPTY_HASH;
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values[pos].~TValue();
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keys[pos].~TKey();
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num_elements--;
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}
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/**
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* reserves space for a number of elements, useful to avoid many resizes and rehashes
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* if adding a known (possibly large) number of elements at once, must be larger than old
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* capacity.
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**/
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void reserve(uint32_t p_new_capacity) {
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ERR_FAIL_COND(p_new_capacity < capacity);
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_resize_and_rehash(p_new_capacity);
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}
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struct Iterator {
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bool valid;
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const TKey *key;
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TValue *value;
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private:
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uint32_t pos;
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friend class OAHashMap;
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};
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Iterator iter() const {
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Iterator it;
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it.valid = true;
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it.pos = 0;
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return next_iter(it);
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}
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Iterator next_iter(const Iterator &p_iter) const {
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if (!p_iter.valid) {
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return p_iter;
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}
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Iterator it;
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it.valid = false;
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it.pos = p_iter.pos;
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it.key = NULL;
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it.value = NULL;
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for (uint32_t i = it.pos; i < capacity; i++) {
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it.pos = i + 1;
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if (hashes[i] == EMPTY_HASH) {
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continue;
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}
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it.valid = true;
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it.key = &keys[i];
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it.value = &values[i];
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return it;
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}
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return it;
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}
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OAHashMap(const OAHashMap &) = delete; // Delete the copy constructor so we don't get unexpected copies and dangling pointers.
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OAHashMap &operator=(const OAHashMap &) = delete; // Same for assignment operator.
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OAHashMap(uint32_t p_initial_capacity = 64) {
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capacity = p_initial_capacity;
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num_elements = 0;
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keys = static_cast<TKey *>(Memory::alloc_static(sizeof(TKey) * capacity));
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values = static_cast<TValue *>(Memory::alloc_static(sizeof(TValue) * capacity));
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hashes = static_cast<uint32_t *>(Memory::alloc_static(sizeof(uint32_t) * capacity));
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for (uint32_t i = 0; i < p_initial_capacity; i++) {
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hashes[i] = EMPTY_HASH;
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}
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}
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~OAHashMap() {
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for (uint32_t i = 0; i < capacity; i++) {
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if (hashes[i] == EMPTY_HASH) {
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continue;
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}
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values[i].~TValue();
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keys[i].~TKey();
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}
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Memory::free_static(keys);
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Memory::free_static(values);
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Memory::free_static(hashes);
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}
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};
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#endif
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