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// MIT License
// Copyright (c) 2019 Erin Catto
// 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.
#include "box2d/b2_block_allocator.h"
#include <limits.h>
#include <string.h>
#include <stddef.h>
static const int32 b2_chunkSize = 16 * 1024;
static const int32 b2_maxBlockSize = 640;
static const int32 b2_chunkArrayIncrement = 128;
// These are the supported object sizes. Actual allocations are rounded up the next size.
static const int32 b2_blockSizes[b2_blockSizeCount] =
{
16, // 0
32, // 1
64, // 2
96, // 3
128, // 4
160, // 5
192, // 6
224, // 7
256, // 8
320, // 9
384, // 10
448, // 11
512, // 12
640, // 13
};
// This maps an arbitrary allocation size to a suitable slot in b2_blockSizes.
struct b2SizeMap
{
b2SizeMap()
{
int32 j = 0;
values[0] = 0;
for (int32 i = 1; i <= b2_maxBlockSize; ++i)
{
b2Assert(j < b2_blockSizeCount);
if (i <= b2_blockSizes[j])
{
values[i] = (uint8)j;
}
else
{
++j;
values[i] = (uint8)j;
}
}
}
uint8 values[b2_maxBlockSize + 1];
};
static const b2SizeMap b2_sizeMap;
struct b2Chunk
{
int32 blockSize;
b2Block* blocks;
};
struct b2Block
{
b2Block* next;
};
b2BlockAllocator::b2BlockAllocator()
{
b2Assert(b2_blockSizeCount < UCHAR_MAX);
m_chunkSpace = b2_chunkArrayIncrement;
m_chunkCount = 0;
m_chunks = (b2Chunk*)b2Alloc(m_chunkSpace * sizeof(b2Chunk));
memset(m_chunks, 0, m_chunkSpace * sizeof(b2Chunk));
memset(m_freeLists, 0, sizeof(m_freeLists));
}
b2BlockAllocator::~b2BlockAllocator()
{
for (int32 i = 0; i < m_chunkCount; ++i)
{
b2Free(m_chunks[i].blocks);
}
b2Free(m_chunks);
}
void* b2BlockAllocator::Allocate(int32 size)
{
if (size == 0)
{
return nullptr;
}
b2Assert(0 < size);
if (size > b2_maxBlockSize)
{
return b2Alloc(size);
}
int32 index = b2_sizeMap.values[size];
b2Assert(0 <= index && index < b2_blockSizeCount);
if (m_freeLists[index])
{
b2Block* block = m_freeLists[index];
m_freeLists[index] = block->next;
return block;
}
else
{
if (m_chunkCount == m_chunkSpace)
{
b2Chunk* oldChunks = m_chunks;
m_chunkSpace += b2_chunkArrayIncrement;
m_chunks = (b2Chunk*)b2Alloc(m_chunkSpace * sizeof(b2Chunk));
memcpy(m_chunks, oldChunks, m_chunkCount * sizeof(b2Chunk));
memset(m_chunks + m_chunkCount, 0, b2_chunkArrayIncrement * sizeof(b2Chunk));
b2Free(oldChunks);
}
b2Chunk* chunk = m_chunks + m_chunkCount;
chunk->blocks = (b2Block*)b2Alloc(b2_chunkSize);
#if defined(_DEBUG)
memset(chunk->blocks, 0xcd, b2_chunkSize);
#endif
int32 blockSize = b2_blockSizes[index];
chunk->blockSize = blockSize;
int32 blockCount = b2_chunkSize / blockSize;
b2Assert(blockCount * blockSize <= b2_chunkSize);
for (int32 i = 0; i < blockCount - 1; ++i)
{
b2Block* block = (b2Block*)((int8*)chunk->blocks + blockSize * i);
b2Block* next = (b2Block*)((int8*)chunk->blocks + blockSize * (i + 1));
block->next = next;
}
b2Block* last = (b2Block*)((int8*)chunk->blocks + blockSize * (blockCount - 1));
last->next = nullptr;
m_freeLists[index] = chunk->blocks->next;
++m_chunkCount;
return chunk->blocks;
}
}
void b2BlockAllocator::Free(void* p, int32 size)
{
if (size == 0)
{
return;
}
b2Assert(0 < size);
if (size > b2_maxBlockSize)
{
b2Free(p);
return;
}
int32 index = b2_sizeMap.values[size];
b2Assert(0 <= index && index < b2_blockSizeCount);
#if defined(_DEBUG)
// Verify the memory address and size is valid.
int32 blockSize = b2_blockSizes[index];
bool found = false;
for (int32 i = 0; i < m_chunkCount; ++i)
{
b2Chunk* chunk = m_chunks + i;
if (chunk->blockSize != blockSize)
{
b2Assert( (int8*)p + blockSize <= (int8*)chunk->blocks ||
(int8*)chunk->blocks + b2_chunkSize <= (int8*)p);
}
else
{
if ((int8*)chunk->blocks <= (int8*)p && (int8*)p + blockSize <= (int8*)chunk->blocks + b2_chunkSize)
{
found = true;
}
}
}
b2Assert(found);
memset(p, 0xfd, blockSize);
#endif
b2Block* block = (b2Block*)p;
block->next = m_freeLists[index];
m_freeLists[index] = block;
}
void b2BlockAllocator::Clear()
{
for (int32 i = 0; i < m_chunkCount; ++i)
{
b2Free(m_chunks[i].blocks);
}
m_chunkCount = 0;
memset(m_chunks, 0, m_chunkSpace * sizeof(b2Chunk));
memset(m_freeLists, 0, sizeof(m_freeLists));
}
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