556 lines
20 KiB
C++
556 lines
20 KiB
C++
/*
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* <Short Description>
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* Copyright (C) 2023 Brett Terpstra
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#ifndef BLT_ALLOCATOR_H
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#include <optional>
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#include <limits>
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#include <vector>
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#include <blt/std/utility.h>
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#include <blt/std/types.h>
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#include <blt/compatibility.h>
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#include <stdexcept>
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#include "logging.h"
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namespace blt
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{
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template<typename value_type, typename pointer, typename const_pointer>
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class allocator_base
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{
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public:
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template<class U, class... Args>
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inline void construct(U* p, Args&& ... args)
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{
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::new((void*) p) U(std::forward<Args>(args)...);
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}
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template<class U>
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inline void destroy(U* p)
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{
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if (p != nullptr)
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p->~U();
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}
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[[nodiscard]] inline size_t max_size() const
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{
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return std::numeric_limits<size_t>::max();
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}
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inline const_pointer address(const value_type& val)
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{
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return std::addressof(val);
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}
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inline pointer address(value_type& val)
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{
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return std::addressof(val);
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}
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};
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template<typename T, size_t BLOCK_SIZE = 8192>
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class area_allocator : public allocator_base<T, T*, const T*>
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{
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public:
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using value = T;
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using type = T;
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using value_type = type;
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using pointer = type*;
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using const_pointer = const type*;
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using void_pointer = void*;
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using const_void_pointer = const void*;
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using reference = value_type&;
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using const_reference = const value_type&;
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using size_type = size_t;
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using difference_type = size_t;
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using propagate_on_container_move_assignment = std::false_type;
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template<class U>
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struct rebind
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{
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typedef blt::area_allocator<U, BLOCK_SIZE> other;
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};
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using allocator_base<value_type, pointer, const_pointer>::allocator_base;
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private:
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/**
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* Stores a view to a region of memory that has been deallocated
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* This is a non-owning reference to the memory block
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*
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* pointer p is the pointer to the beginning of the block of memory
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* size_t n is the number of elements that this block can hold
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*/
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struct pointer_view
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{
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pointer p;
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size_t n;
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};
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/**
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* Stores the actual data for allocated blocks. Since we would like to be able to allocate an arbitrary number of items
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* we need a way of storing that data. The block storage holds an owning pointer to a region of memory with used elements
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* Only up to used has to have their destructors called, which should be handled by the deallocate function
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* it is UB to not deallocate memory allocated by this allocator
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*
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* an internal vector is used to store the regions of memory which have been deallocated. the allocate function will search for
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* free blocks with sufficient size in order to maximize memory usage. In the future more advanced methods should be used
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* for both faster access to deallocated blocks of sufficient size and to ensure coherent memory.
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*/
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struct block_storage
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{
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pointer data;
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size_t used = 0;
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// TODO: b-tree?
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std::vector<pointer_view> unallocated_blocks;
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};
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/**
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* Stores an index to a pointer_view along with the amount of memory leftover after the allocation
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* it also stores the block being allocated to in question. The new inserted leftover should start at old_ptr + size
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*/
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struct block_view
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{
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block_storage* blk;
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size_t index;
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size_t leftover;
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block_view(block_storage* blk, size_t index, size_t leftover): blk(blk), index(index), leftover(leftover)
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{}
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};
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/**
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* Allocate a new block of memory and push it to the back of blocks.
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*/
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inline void allocate_block()
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{
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//BLT_INFO("Allocating a new block of size %d", BLOCK_SIZE);
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auto* blk = new block_storage();
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blk->data = static_cast<pointer>(malloc(sizeof(T) * BLOCK_SIZE));
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blocks.push_back(blk);
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}
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/**
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* Searches for a free block inside the block storage with sufficient space and returns an optional view to it
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* The optional will be empty if no open block can be found.
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*/
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inline std::optional<block_view> search_for_block(block_storage* blk, size_t n)
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{
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for (auto kv : blt::enumerate(blk->unallocated_blocks))
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{
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if (kv.second.n >= n)
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return block_view{blk, kv.first, kv.second.n - n};
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}
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return {};
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}
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/**
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* removes the block of memory from the unallocated_blocks storage in the underlying block, inserting a new unallocated block if
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* there was any leftover. Returns a pointer to the beginning of the new block.
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*/
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inline pointer swap_pop_resize_if(const block_view& view, size_t n)
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{
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pointer_view ptr = view.blk->unallocated_blocks[view.index];
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std::iter_swap(view.blk->unallocated_blocks.begin() + view.index, view.blk->unallocated_blocks.end() - 1);
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view.blk->unallocated_blocks.pop_back();
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if (view.leftover > 0)
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view.blk->unallocated_blocks.push_back({ptr.p + n, view.leftover});
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return ptr.p;
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}
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/**
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* Finds the next available unallocated block of memory, or empty if there is none which meet size requirements
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*/
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inline std::optional<pointer> find_available_block(size_t n)
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{
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for (auto* blk : blocks)
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{
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if (auto view = search_for_block(blk, n))
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return swap_pop_resize_if(view.value(), n);
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}
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return {};
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}
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/**
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* returns a pointer to a block of memory along with an offset into that pointer that the requested block can be found at
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*/
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inline std::pair<pointer, size_t> getBlock(size_t n)
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{
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if (auto blk = find_available_block(n))
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return {blk.value(), 0};
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if (blocks.back()->used + n > BLOCK_SIZE)
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allocate_block();
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auto ptr = std::pair<pointer, size_t>{blocks.back()->data, blocks.back()->used};
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blocks.back()->used += n;
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return ptr;
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}
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/**
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* Calls the constructor on elements if they require construction, otherwise constructor will not be called and this function is useless
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*
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* ALLOCATORS RETURN UNINIT STORAGE!! THIS HAS BEEN DISABLED.
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*/
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inline void allocate_in_block(pointer, size_t)
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{
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// if constexpr (std::is_default_constructible_v<T> && !std::is_trivially_default_constructible_v<T>)
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// {
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// for (size_t i = 0; i < n; i++)
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// new(&begin[i]) T();
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// }
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}
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public:
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area_allocator()
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{
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allocate_block();
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}
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area_allocator(const area_allocator& copy) = delete;
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area_allocator(area_allocator&& move) noexcept
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{
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blocks = move.blocks;
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}
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area_allocator& operator=(const area_allocator& copy) = delete;
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area_allocator& operator=(area_allocator&& move) noexcept
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{
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std::swap(move.blocks, blocks);
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}
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[[nodiscard]] pointer allocate(size_t n)
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{
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if (n > BLOCK_SIZE)
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throw std::runtime_error("Requested allocation is too large!");
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auto block_info = getBlock(n);
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auto* ptr = &block_info.first[block_info.second];
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// call constructors on the objects if they require it
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allocate_in_block(ptr, n);
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return ptr;
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}
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void deallocate(pointer p, size_t n) noexcept
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{
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if (p == nullptr)
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return;
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// for (size_t i = 0; i < n; i++)
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// p[i].~T();
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for (auto*& blk : blocks)
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{
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if (p >= blk->data && p <= (blk->data + BLOCK_SIZE))
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{
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blk->unallocated_blocks.push_back(pointer_view{p, n});
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break;
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}
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}
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}
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~area_allocator()
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{
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for (auto*& blk : blocks)
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{
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free(blk->data);
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delete blk;
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}
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}
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private:
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std::vector<block_storage*> blocks;
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};
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// template<typename T>
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// class bump_allocator : public allocator_base<T, T*, const T*>
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// {
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// public:
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// using value = T;
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// using type = T;
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// using value_type = type;
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// using pointer = type*;
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// using const_pointer = const type*;
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// using void_pointer = void*;
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// using const_void_pointer = const void*;
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// using reference = value_type&;
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// using const_reference = const value_type&;
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// using size_type = size_t;
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// using difference_type = size_t;
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// using propagate_on_container_move_assignment = std::false_type;
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// template<class U>
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// struct rebind
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// {
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// typedef blt::bump_allocator<U> other;
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// };
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// using allocator_base<value_type, pointer, const_pointer>::allocator_base;
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// private:
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// pointer buffer_;
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// blt::size_t offset_;
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// blt::size_t size_;
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// public:
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// explicit bump_allocator(blt::size_t size): buffer_(static_cast<pointer>(malloc(size * sizeof(T)))), offset_(0), size_(size)
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// {}
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//
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// template<typename... Args>
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// explicit bump_allocator(blt::size_t size, Args&& ... defaults):
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// buffer_(static_cast<pointer>(malloc(size * sizeof(type)))), offset_(0), size_(size)
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// {
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// for (blt::size_t i = 0; i < size_; i++)
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// ::new(&buffer_[i]) T(std::forward<Args>(defaults)...);
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// }
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//
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// bump_allocator(pointer buffer, blt::size_t size): buffer_(buffer), offset_(0), size_(size)
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// {}
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//
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// bump_allocator(const bump_allocator& copy) = delete;
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//
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// bump_allocator(bump_allocator&& move) noexcept
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// {
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// buffer_ = move.buffer_;
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// size_ = move.size_;
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// offset_ = move.offset_;
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// }
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//
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// bump_allocator& operator=(const bump_allocator& copy) = delete;
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//
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// bump_allocator& operator=(bump_allocator&& move) noexcept
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// {
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// std::swap(move.buffer_, buffer_);
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// std::swap(move.size_, size_);
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// std::swap(move.offset_, offset_);
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// }
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//
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// pointer allocate(blt::size_t n)
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// {
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// auto nv = offset_ + n;
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// if (nv > size_)
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// throw std::bad_alloc();
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// pointer b = &buffer_[offset_];
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// offset_ = nv;
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// return b;
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// }
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//
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// void deallocate(pointer, blt::size_t)
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// {}
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//
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// ~bump_allocator()
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// {
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// free(buffer_);
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// }
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// };
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/**
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* The bump allocator is meant to be a faster area allocator which will only allocate forward through either a supplied buffer or size
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* or will create a linked list type data structure of buffered blocks.
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* @tparam ALLOC allocator to use for any allocations. In the case of the non-linked variant, this will be used if a size is supplied. The supplied buffer must be allocated with this allocator!
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* @tparam linked use a linked list to allocate with the allocator or just use the supplied buffer and throw an exception of we cannot allocate
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*/
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template<bool linked, template<typename> typename ALLOC = std::allocator>
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class bump_allocator;
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template<template<typename> typename ALLOC>
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class bump_allocator<false, ALLOC>
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{
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private:
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ALLOC<blt::u8> allocator;
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blt::u8* buffer_;
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blt::u8* offset_;
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blt::size_t size_;
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public:
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explicit bump_allocator(blt::size_t size): buffer_(static_cast<blt::u8*>(allocator.allocate(size))), offset_(buffer_), size_(size)
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{}
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explicit bump_allocator(blt::u8* buffer, blt::size_t size): buffer_(buffer), offset_(buffer), size_(size)
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{}
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template<typename T>
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[[nodiscard]] T* allocate()
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{
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size_t remaining_num_bytes = size_ - static_cast<size_t>(buffer_ - offset_);
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auto pointer = static_cast<void*>(offset_);
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const auto aligned_address = std::align(alignof(T), sizeof(T), pointer, remaining_num_bytes);
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if (aligned_address == nullptr)
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throw std::bad_alloc{};
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offset_ = static_cast<blt::u8*>(aligned_address) + sizeof(T);
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return static_cast<T*>(aligned_address);
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}
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template<typename T, typename... Args>
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[[nodiscard]] T* emplace(Args&& ... args)
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{
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const auto allocated_memory = allocate<T>();
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return new(allocated_memory) T{std::forward<Args>(args)...};
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}
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template<class U, class... Args>
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inline void construct(U* p, Args&& ... args)
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{
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::new((void*) p) U(std::forward<Args>(args)...);
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}
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template<class U>
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inline void destroy(U* p)
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{
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if (p != nullptr)
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p->~U();
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}
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~bump_allocator()
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{
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allocator.deallocate(buffer_, size_);
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}
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};
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template<template<typename> typename ALLOC>
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class bump_allocator<true, ALLOC>
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{
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private:
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struct block
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{
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blt::u8* buffer = nullptr;
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blt::size_t offset = 0;
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blt::size_t allocated_objects = 0;
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blt::size_t deallocated_objects = 0;
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};
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ALLOC<blt::u8> allocator;
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std::vector<block, ALLOC<block>> blocks;
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blt::size_t size_;
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void expand()
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{
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blocks.push_back({static_cast<blt::u8*>(allocator.allocate(size_)), 0});
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}
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template<typename T>
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T* allocate_back()
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{
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auto& back = blocks.back();
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size_t remaining_bytes = size_ - back.offset;
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auto void_ptr = reinterpret_cast<void*>(&back.buffer[back.offset]);
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auto new_ptr = static_cast<blt::u8*>(std::align(alignof(T), sizeof(T), void_ptr, remaining_bytes));
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if (new_ptr == nullptr)
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expand();
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else
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{
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back.offset += (back.buffer - new_ptr + sizeof(T));
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back.allocated_objects++;
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}
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return reinterpret_cast<T*>(new_ptr);
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}
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public:
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/**
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* @param size of the list blocks
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*/
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explicit bump_allocator(blt::size_t size): size_(size)
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{
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expand();
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}
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template<typename T>
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[[nodiscard]] T* allocate()
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{
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if (blocks.back().offset + sizeof(T) > size_)
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expand();
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if (auto ptr = allocate_back<T>(); ptr == nullptr)
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{
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BLT_INFO("Not enough space for me");
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expand();
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} else
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return ptr;
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if (auto ptr = allocate_back<T>(); ptr == nullptr)
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throw std::bad_alloc();
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else
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return ptr;
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}
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template<typename T>
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void deallocate(T* p)
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{
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auto* ptr = reinterpret_cast<blt::u8*>(p);
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blt::i64 remove_index = -1;
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for (auto e : blt::enumerate(blocks))
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{
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auto& block = e.second;
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if (ptr >= block.buffer && ptr <= &block.buffer[block.offset])
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{
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block.deallocated_objects++;
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if (block.deallocated_objects == block.allocated_objects)
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remove_index = static_cast<blt::i64>(e.first);
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break;
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}
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}
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if (remove_index < 0)
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return;
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std::iter_swap(blocks.begin() + remove_index, blocks.end() - 1);
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allocator.deallocate(blocks.back().buffer, size_);
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BLT_DEBUG("I have freed a block!");
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blocks.pop_back();
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}
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template<typename T, typename... Args>
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[[nodiscard]] T* emplace(Args&& ... args)
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{
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const auto allocated_memory = allocate<T>();
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return new(allocated_memory) T{std::forward<Args>(args)...};
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}
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template<class U, class... Args>
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inline void construct(U* p, Args&& ... args)
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{
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::new((void*) p) U(std::forward<Args>(args)...);
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}
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template<class U>
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inline void destroy(U* p)
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{
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if (p != nullptr)
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p->~U();
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}
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~bump_allocator()
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{
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for (auto& v : blocks)
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allocator.deallocate(v.buffer, size_);
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}
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};
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template<typename T>
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class constexpr_allocator
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{
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public:
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constexpr constexpr_allocator() = default;
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constexpr T* allocate(blt::size_t n)
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{
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return ::new T[n];
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}
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constexpr void deallocate(T* t, blt::size_t)
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{
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::delete[] t;
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}
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BLT_CPP20_CONSTEXPR ~constexpr_allocator() = default;
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};
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}
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#define BLT_ALLOCATOR_H
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#endif //BLT_ALLOCATOR_H
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