forked from 0ad/0ad
vladislavbelov
9ed3b88d25
Differential Revision: https://code.wildfiregames.com/D3609 This was SVN commit r24968.
162 lines
3.6 KiB
C++
162 lines
3.6 KiB
C++
/* Copyright (C) 2021 Wildfire Games.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#ifndef INCLUDED_ALLOCATORS_DYNAMIC_ARENA
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#define INCLUDED_ALLOCATORS_DYNAMIC_ARENA
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#include "lib/bits.h"
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#include <cstdlib>
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#include <new> // bad_alloc
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#include <utility>
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#include <vector>
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namespace Allocators {
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/**
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* 'Blind' memory allocator. Characteristics:
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* - grows dynamically, and linearily, by BLOCK_SIZE
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* - no reallocations, pointers remain valid
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* - can allocate objects up to BLOCK_SIZE in size
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* - can handle any aligment (up to BLOCK_SIZE)
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* - Doesn't de-allocate unless cleared or destroyed.
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*/
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template<size_t BLOCK_SIZE>
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class DynamicArena
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{
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protected:
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class Block
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{
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public:
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Block()
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{
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m_Data = static_cast<uint8_t*>(
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std::malloc(BLOCK_SIZE * sizeof(uint8_t)));
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if (!m_Data)
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{
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debug_warn("DynamicArena failed to allocate chunk");
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throw std::bad_alloc();
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}
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}
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~Block()
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{
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std::free(static_cast<void*>(m_Data));
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}
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Block(const Block& other) = delete;
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Block& operator=(const Block& other) = delete;
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Block(Block&& other)
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: m_Size(other.m_Size), m_Data(other.m_Data)
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{
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other.m_Size = 0;
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other.m_Data = nullptr;
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}
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Block& operator=(Block&& other)
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{
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if (&other == this)
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return *this;
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Block tmp(std::move(other));
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swap(*this, tmp);
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return *this;
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}
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friend void swap(Block& lhs, Block& rhs)
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{
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using std::swap;
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swap(lhs.m_Size, rhs.m_Size);
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swap(lhs.m_Data, rhs.m_Data);
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}
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bool Available(size_t n, size_t alignment) const
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{
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return n + ROUND_UP(m_Size, alignment) <= BLOCK_SIZE;
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}
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uint8_t* Allocate(size_t n, size_t alignment)
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{
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m_Size = ROUND_UP(m_Size, alignment);
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uint8_t* ptr = &m_Data[m_Size];
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m_Size += n;
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return ptr;
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}
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private:
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size_t m_Size = 0;
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uint8_t* m_Data = nullptr;
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};
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NONCOPYABLE(DynamicArena);
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public:
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DynamicArena()
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{
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m_Blocks.reserve(16);
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AllocateNewBlock();
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};
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void AllocateNewBlock()
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{
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m_Blocks.emplace_back();
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}
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void* allocate(size_t n, const void*, size_t alignment)
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{
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// Safely handle zero-sized allocations (happens with GCC STL - see ticket #909).
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if (n == 0)
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n = 1;
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if (n > BLOCK_SIZE)
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{
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debug_warn("DynamicArena cannot allocate more than chunk size");
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throw std::bad_alloc();
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}
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if (!m_Blocks.back().Available(n, alignment))
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AllocateNewBlock();
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return reinterpret_cast<void*>(m_Blocks.back().Allocate(n, alignment));
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}
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void deallocate(void* UNUSED(p), size_t UNUSED(n))
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{
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// ignored
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}
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void clear()
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{
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m_Blocks.clear();
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AllocateNewBlock();
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}
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protected:
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std::vector<Block> m_Blocks;
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};
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} // namespace Allocators
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#endif // INCLUDED_ALLOCATORS_DYNAMIC_ARENA
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