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/**************************************************************************/
/* pooled_list.h */
/**************************************************************************/
/* This file is part of: */
/* REDOT ENGINE */
/* https://redotengine.org */
/**************************************************************************/
/* Copyright (c) 2024-present Redot Engine contributors */
/* (see REDOT_AUTHORS.md) */
/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
/* */
/* 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 POOLED_LIST_H
#define POOLED_LIST_H
// Simple template to provide a pool with O(1) allocate and free.
// The freelist could alternatively be a linked list placed within the unused elements
// to use less memory, however a separate freelist is probably more cache friendly.
// NOTE : Take great care when using this with non POD types. The construction and destruction
// is done in the LocalVector, NOT as part of the pool. So requesting a new item does not guarantee
// a constructor is run, and free does not guarantee a destructor.
// You should generally handle clearing
// an item explicitly after a request, as it may contain 'leftovers'.
// This is by design for fastest use in the BVH. If you want a more general pool
// that does call constructors / destructors on request / free, this should probably be
// a separate template.
// The zero_on_first_request feature is optional and is useful for e.g. pools of handles,
// which may use a ref count which we want to be initialized to zero the first time a handle is created,
// but left alone on subsequent allocations (as will typically be incremented).
// Note that there is no function to compact the pool - this would
// invalidate any existing pool IDs held externally.
// Compaction can be done but would rely on a more complex method
// of preferentially giving out lower IDs in the freelist first.
#include "core/templates/local_vector.h"
template <typename T, typename U = uint32_t, bool force_trivial = false, bool zero_on_first_request = false>
class PooledList {
LocalVector<T, U, force_trivial> list;
LocalVector<U, U, true> freelist;
// not all list members are necessarily used
U _used_size;
public:
PooledList() {
_used_size = 0;
}
// Use with care, in most cases you should make sure to
// free all elements first (i.e. _used_size would be zero),
// although it could also be used without this as an optimization
// in some cases.
void clear() {
list.clear();
freelist.clear();
_used_size = 0;
}
uint64_t estimate_memory_use() const {
return ((uint64_t)list.size() * sizeof(T)) + ((uint64_t)freelist.size() * sizeof(U));
}
const T &operator[](U p_index) const {
return list[p_index];
}
T &operator[](U p_index) {
return list[p_index];
}
// To be explicit in a pool there is a distinction
// between the number of elements that are currently
// in use, and the number of elements that have been reserved.
// Using size() would be vague.
U used_size() const { return _used_size; }
U reserved_size() const { return list.size(); }
T *request(U &r_id) {
_used_size++;
if (freelist.size()) {
// pop from freelist
int new_size = freelist.size() - 1;
r_id = freelist[new_size];
freelist.resize(new_size);
return &list[r_id];
}
r_id = list.size();
list.resize(r_id + 1);
static_assert((!zero_on_first_request) || (__is_pod(T)), "zero_on_first_request requires trivial type");
if constexpr (zero_on_first_request && __is_pod(T)) {
list[r_id] = {};
}
return &list[r_id];
}
void free(const U &p_id) {
// should not be on free list already
ERR_FAIL_UNSIGNED_INDEX(p_id, list.size());
freelist.push_back(p_id);
ERR_FAIL_COND_MSG(!_used_size, "_used_size has become out of sync, have you double freed an item?");
_used_size--;
}
};
// a pooled list which automatically keeps a list of the active members
template <typename T, typename U = uint32_t, bool force_trivial = false, bool zero_on_first_request = false>
class TrackedPooledList {
public:
U pool_used_size() const { return _pool.used_size(); }
U pool_reserved_size() const { return _pool.reserved_size(); }
U active_size() const { return _active_list.size(); }
// use with care, see the earlier notes in the PooledList clear()
void clear() {
_pool.clear();
_active_list.clear();
_active_map.clear();
}
U get_active_id(U p_index) const {
return _active_list[p_index];
}
const T &get_active(U p_index) const {
return _pool[get_active_id(p_index)];
}
T &get_active(U p_index) {
return _pool[get_active_id(p_index)];
}
const T &operator[](U p_index) const {
return _pool[p_index];
}
T &operator[](U p_index) {
return _pool[p_index];
}
T *request(U &r_id) {
T *item = _pool.request(r_id);
// add to the active list
U active_list_id = _active_list.size();
_active_list.push_back(r_id);
// expand the active map (this should be in sync with the pool list
if (_pool.used_size() > _active_map.size()) {
_active_map.resize(_pool.used_size());
}
// store in the active map
_active_map[r_id] = active_list_id;
return item;
}
void free(const U &p_id) {
_pool.free(p_id);
// remove from the active list.
U list_id = _active_map[p_id];
// zero the _active map to detect bugs (only in debug?)
_active_map[p_id] = -1;
_active_list.remove_unordered(list_id);
// keep the replacement in sync with the correct list Id
if (list_id < _active_list.size()) {
// which pool id has been replaced in the active list
U replacement_id = _active_list[list_id];
// keep that replacements map up to date with the new position
_active_map[replacement_id] = list_id;
}
}
const LocalVector<U, U> &get_active_list() const { return _active_list; }
private:
PooledList<T, U, force_trivial, zero_on_first_request> _pool;
LocalVector<U, U> _active_map;
LocalVector<U, U> _active_list;
};
#endif // POOLED_LIST_H
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