84 lines
2.0 KiB
C++
84 lines
2.0 KiB
C++
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#pragma once
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#include <algorithm>
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#include <array>
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#include <bit>
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#include <boost/assert.hpp>
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#include <cstdlib>
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#include <iostream>
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#include <new>
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#include <vector>
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namespace osrm::util
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{
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template <typename T> class PoolAllocator
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{
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public:
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using value_type = T;
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T *allocate(std::size_t n)
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{
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size_t free_list_index = get_next_power_of_two_exponent(n);
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auto &free_list = free_lists_[free_list_index];
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const auto items_in_block = 1u << free_list_index;
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if (free_list.empty())
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{
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// Check if there is space in current block
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if (current_block_left_items_ < items_in_block)
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{
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allocate_block(items_in_block);
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}
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free_list.push_back(current_block_ptr_);
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current_block_left_items_ -= items_in_block;
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current_block_ptr_ += items_in_block;
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}
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auto ptr = free_list.back();
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free_list.pop_back();
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return ptr;
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}
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void deallocate(T *p, std::size_t n) noexcept
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{
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size_t free_list_index = get_next_power_of_two_exponent(n);
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free_lists_[free_list_index].push_back(p);
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}
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~PoolAllocator()
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{
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for (auto block : blocks_)
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{
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std::free(block);
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}
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}
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private:
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size_t get_next_power_of_two_exponent(size_t n) const
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{
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return std::countr_zero(std::bit_ceil(n));
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}
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void allocate_block(size_t items_in_block)
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{
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size_t block_size = std::max(items_in_block, (size_t)256) * sizeof(T);
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T *block = static_cast<T *>(std::malloc(block_size));
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if (!block)
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{
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throw std::bad_alloc();
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}
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blocks_.push_back(block);
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current_block_ = block;
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current_block_ptr_ = block;
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current_block_left_items_ = block_size / sizeof(T);
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}
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std::array<std::vector<T *>, 32> free_lists_;
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std::vector<T *> blocks_;
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T *current_block_ = nullptr;
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T *current_block_ptr_ = nullptr;
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size_t current_block_left_items_ = 0;
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};
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} // namespace osrm::util
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