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212 lines
7.5 KiB
C++
212 lines
7.5 KiB
C++
/**************************************************************************/
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/* pooled_list.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) 2014-present Godot Engine contributors (see AUTHORS.md). */
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/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
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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 POOLED_LIST_H
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#define POOLED_LIST_H
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// Simple template to provide a pool with O(1) allocate and free.
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// The freelist could alternatively be a linked list placed within the unused elements
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// to use less memory, however a separate freelist is probably more cache friendly.
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// NOTE : Take great care when using this with non POD types. The construction and destruction
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// is done in the LocalVector, NOT as part of the pool. So requesting a new item does not guarantee
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// a constructor is run, and free does not guarantee a destructor.
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// You should generally handle clearing
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// an item explicitly after a request, as it may contain 'leftovers'.
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// This is by design for fastest use in the BVH. If you want a more general pool
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// that does call constructors / destructors on request / free, this should probably be
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// a separate template.
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// The zero_on_first_request feature is optional and is useful for e.g. pools of handles,
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// which may use a ref count which we want to be initialized to zero the first time a handle is created,
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// but left alone on subsequent allocations (as will typically be incremented).
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// Note that there is no function to compact the pool - this would
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// invalidate any existing pool IDs held externally.
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// Compaction can be done but would rely on a more complex method
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// of preferentially giving out lower IDs in the freelist first.
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#include "core/templates/local_vector.h"
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template <typename T, typename U = uint32_t, bool force_trivial = false, bool zero_on_first_request = false>
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class PooledList {
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LocalVector<T, U, force_trivial> list;
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LocalVector<U, U, true> freelist;
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// not all list members are necessarily used
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U _used_size;
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public:
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PooledList() {
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_used_size = 0;
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}
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// Use with care, in most cases you should make sure to
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// free all elements first (i.e. _used_size would be zero),
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// although it could also be used without this as an optimization
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// in some cases.
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void clear() {
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list.clear();
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freelist.clear();
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_used_size = 0;
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}
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uint64_t estimate_memory_use() const {
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return ((uint64_t)list.size() * sizeof(T)) + ((uint64_t)freelist.size() * sizeof(U));
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}
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const T &operator[](U p_index) const {
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return list[p_index];
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}
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T &operator[](U p_index) {
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return list[p_index];
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}
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// To be explicit in a pool there is a distinction
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// between the number of elements that are currently
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// in use, and the number of elements that have been reserved.
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// Using size() would be vague.
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U used_size() const { return _used_size; }
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U reserved_size() const { return list.size(); }
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T *request(U &r_id) {
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_used_size++;
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if (freelist.size()) {
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// pop from freelist
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int new_size = freelist.size() - 1;
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r_id = freelist[new_size];
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freelist.resize(new_size);
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return &list[r_id];
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}
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r_id = list.size();
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list.resize(r_id + 1);
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static_assert((!zero_on_first_request) || (__is_pod(T)), "zero_on_first_request requires trivial type");
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if constexpr (zero_on_first_request && __is_pod(T)) {
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list[r_id] = {};
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}
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return &list[r_id];
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}
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void free(const U &p_id) {
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// should not be on free list already
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ERR_FAIL_UNSIGNED_INDEX(p_id, list.size());
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freelist.push_back(p_id);
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ERR_FAIL_COND_MSG(!_used_size, "_used_size has become out of sync, have you double freed an item?");
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_used_size--;
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}
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};
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// a pooled list which automatically keeps a list of the active members
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template <typename T, typename U = uint32_t, bool force_trivial = false, bool zero_on_first_request = false>
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class TrackedPooledList {
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public:
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U pool_used_size() const { return _pool.used_size(); }
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U pool_reserved_size() const { return _pool.reserved_size(); }
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U active_size() const { return _active_list.size(); }
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// use with care, see the earlier notes in the PooledList clear()
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void clear() {
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_pool.clear();
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_active_list.clear();
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_active_map.clear();
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}
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U get_active_id(U p_index) const {
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return _active_list[p_index];
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}
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const T &get_active(U p_index) const {
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return _pool[get_active_id(p_index)];
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}
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T &get_active(U p_index) {
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return _pool[get_active_id(p_index)];
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}
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const T &operator[](U p_index) const {
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return _pool[p_index];
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}
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T &operator[](U p_index) {
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return _pool[p_index];
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}
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T *request(U &r_id) {
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T *item = _pool.request(r_id);
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// add to the active list
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U active_list_id = _active_list.size();
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_active_list.push_back(r_id);
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// expand the active map (this should be in sync with the pool list
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if (_pool.used_size() > _active_map.size()) {
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_active_map.resize(_pool.used_size());
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}
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// store in the active map
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_active_map[r_id] = active_list_id;
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return item;
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}
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void free(const U &p_id) {
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_pool.free(p_id);
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// remove from the active list.
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U list_id = _active_map[p_id];
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// zero the _active map to detect bugs (only in debug?)
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_active_map[p_id] = -1;
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_active_list.remove_unordered(list_id);
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// keep the replacement in sync with the correct list Id
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if (list_id < _active_list.size()) {
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// which pool id has been replaced in the active list
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U replacement_id = _active_list[list_id];
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// keep that replacements map up to date with the new position
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_active_map[replacement_id] = list_id;
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}
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}
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const LocalVector<U, U> &get_active_list() const { return _active_list; }
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private:
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PooledList<T, U, force_trivial, zero_on_first_request> _pool;
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LocalVector<U, U> _active_map;
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LocalVector<U, U> _active_list;
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};
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#endif // POOLED_LIST_H
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