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/* Copyright (C) 2021 Wildfire Games.
*
* 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 INCLUDED_ALLOCATORS_DYNAMIC_ARENA
#define INCLUDED_ALLOCATORS_DYNAMIC_ARENA
#include "lib/bits.h"
#include <cstdlib>
#include <new> // bad_alloc
#include <utility>
#include <vector>
namespace Allocators {
/**
* 'Blind' memory allocator. Characteristics:
* - grows dynamically, and linearily, by BLOCK_SIZE
* - no reallocations, pointers remain valid
* - can allocate objects up to BLOCK_SIZE in size
* - can handle any aligment (up to BLOCK_SIZE)
* - Doesn't de-allocate unless cleared or destroyed.
*/
template<size_t BLOCK_SIZE>
class DynamicArena
{
protected:
class Block
{
public:
Block()
{
m_Data = static_cast<uint8_t*>(
std::malloc(BLOCK_SIZE * sizeof(uint8_t)));
if (!m_Data)
{
debug_warn("DynamicArena failed to allocate chunk");
throw std::bad_alloc();
}
}
~Block()
{
std::free(static_cast<void*>(m_Data));
}
Block(const Block& other) = delete;
Block& operator=(const Block& other) = delete;
Block(Block&& other)
: m_Size(other.m_Size), m_Data(other.m_Data)
{
other.m_Size = 0;
other.m_Data = nullptr;
}
Block& operator=(Block&& other)
{
if (&other == this)
return *this;
Block tmp(std::move(other));
swap(*this, tmp);
return *this;
}
friend void swap(Block& lhs, Block& rhs)
{
using std::swap;
swap(lhs.m_Size, rhs.m_Size);
swap(lhs.m_Data, rhs.m_Data);
}
bool Available(size_t n, size_t alignment) const
{
return n + ROUND_UP(m_Size, alignment) <= BLOCK_SIZE;
}
uint8_t* Allocate(size_t n, size_t alignment)
{
m_Size = ROUND_UP(m_Size, alignment);
uint8_t* ptr = &m_Data[m_Size];
m_Size += n;
return ptr;
}
private:
size_t m_Size = 0;
uint8_t* m_Data = nullptr;
};
NONCOPYABLE(DynamicArena);
public:
DynamicArena()
{
m_Blocks.reserve(16);
AllocateNewBlock();
};
void AllocateNewBlock()
{
m_Blocks.emplace_back();
}
void* allocate(size_t n, const void*, size_t alignment)
{
// Safely handle zero-sized allocations (happens with GCC STL - see ticket #909).
if (n == 0)
n = 1;
if (n > BLOCK_SIZE)
{
debug_warn("DynamicArena cannot allocate more than chunk size");
throw std::bad_alloc();
}
if (!m_Blocks.back().Available(n, alignment))
AllocateNewBlock();
return reinterpret_cast<void*>(m_Blocks.back().Allocate(n, alignment));
}
void deallocate(void* UNUSED(p), size_t UNUSED(n))
{
// ignored
}
void clear()
{
m_Blocks.clear();
AllocateNewBlock();
}
protected:
std::vector<Block> m_Blocks;
};
} // namespace Allocators
#endif // INCLUDED_ALLOCATORS_DYNAMIC_ARENA
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