virtualx-engine/core/templates/pooled_list.h

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/*************************************************************************/
/* pooled_list.h */
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/*************************************************************************/
/* This file is part of: */
/* GODOT ENGINE */
/* https://godotengine.org */
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/*************************************************************************/
/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur. */
/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md). */
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/* */
/* 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
#include "core/templates/local_vector.h"
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// 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.
template <class T, bool force_trivial = false>
class PooledList {
LocalVector<T, uint32_t, force_trivial> list;
LocalVector<uint32_t, uint32_t, true> freelist;
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// not all list members are necessarily used
int _used_size;
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public:
PooledList() {
_used_size = 0;
}
int estimate_memory_use() const {
return (list.size() * sizeof(T)) + (freelist.size() * sizeof(uint32_t));
}
const T &operator[](uint32_t p_index) const {
return list[p_index];
}
T &operator[](uint32_t p_index) {
return list[p_index];
}
int size() const { return _used_size; }
T *request(uint32_t &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];
}
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r_id = list.size();
list.resize(r_id + 1);
return &list[r_id];
}
void free(const uint32_t &p_id) {
// should not be on free list already
CRASH_COND(p_id >= list.size());
freelist.push_back(p_id);
_used_size--;
}
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};
#endif // POOLED_LIST_H