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/*************************************************************************/
/* paged_allocator.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 PAGED_ALLOCATOR_H
#define PAGED_ALLOCATOR_H
#include "core/os/memory.h"
#include "core/os/spin_lock.h"
#include "core/typedefs.h"
#include <type_traits>
template <class T, bool thread_safe = false>
class PagedAllocator {
T **page_pool = nullptr;
T ***available_pool = nullptr;
uint32_t pages_allocated = 0;
uint32_t allocs_available = 0;
uint32_t page_shift = 0;
uint32_t page_mask = 0;
uint32_t page_size = 0;
SpinLock spin_lock;
public:
enum {
DEFAULT_PAGE_SIZE = 4096
};
template <class... Args>
T *alloc(const Args &&...p_args) {
if (thread_safe) {
spin_lock.lock();
}
if (unlikely(allocs_available == 0)) {
uint32_t pages_used = pages_allocated;
pages_allocated++;
page_pool = (T **)memrealloc(page_pool, sizeof(T *) * pages_allocated);
available_pool = (T ***)memrealloc(available_pool, sizeof(T **) * pages_allocated);
page_pool[pages_used] = (T *)memalloc(sizeof(T) * page_size);
available_pool[pages_used] = (T **)memalloc(sizeof(T *) * page_size);
for (uint32_t i = 0; i < page_size; i++) {
available_pool[0][i] = &page_pool[pages_used][i];
}
allocs_available += page_size;
}
allocs_available--;
T *alloc = available_pool[allocs_available >> page_shift][allocs_available & page_mask];
if (thread_safe) {
spin_lock.unlock();
}
memnew_placement(alloc, T(p_args...));
return alloc;
}
void free(T *p_mem) {
if (thread_safe) {
spin_lock.lock();
}
p_mem->~T();
available_pool[allocs_available >> page_shift][allocs_available & page_mask] = p_mem;
allocs_available++;
if (thread_safe) {
spin_lock.unlock();
}
}
void reset(bool p_allow_unfreed = false) {
if (!p_allow_unfreed || !std::is_trivially_destructible<T>::value) {
ERR_FAIL_COND(allocs_available < pages_allocated * page_size);
}
if (pages_allocated) {
for (uint32_t i = 0; i < pages_allocated; i++) {
memfree(page_pool[i]);
memfree(available_pool[i]);
}
memfree(page_pool);
memfree(available_pool);
page_pool = nullptr;
available_pool = nullptr;
pages_allocated = 0;
allocs_available = 0;
}
}
bool is_configured() const {
return page_size > 0;
}
void configure(uint32_t p_page_size) {
ERR_FAIL_COND(page_pool != nullptr); //sanity check
ERR_FAIL_COND(p_page_size == 0);
page_size = nearest_power_of_2_templated(p_page_size);
page_mask = page_size - 1;
page_shift = get_shift_from_power_of_2(page_size);
}
// Power of 2 recommended because of alignment with OS page sizes.
// Even if element is bigger, it's still a multiple and gets rounded to amount of pages.
PagedAllocator(uint32_t p_page_size = DEFAULT_PAGE_SIZE) {
configure(p_page_size);
}
~PagedAllocator() {
ERR_FAIL_COND_MSG(allocs_available < pages_allocated * page_size, "Pages in use exist at exit in PagedAllocator");
reset();
}
};
#endif // PAGED_ALLOCATOR_H
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