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#include "memory-pool.h"
#include <cassert>
namespace Slang
{
MemoryPool::MemoryPool(unsigned char * pBuffer, int pLog2BlockSize, int numBlocks)
{
Init(pBuffer, pLog2BlockSize, numBlocks);
}
void MemoryPool::Init(unsigned char * pBuffer, int pLog2BlockSize, int numBlocks)
{
assert(pLog2BlockSize >= 1 && pLog2BlockSize <= 30);
assert(numBlocks >= 4);
buffer = pBuffer;
blockSize = 1 << pLog2BlockSize;
log2BlockSize = pLog2BlockSize;
numLevels = Math::Log2Floor(numBlocks);
freeList[0] = (FreeListNode*)buffer;
freeList[0]->NextPtr = nullptr;
freeList[0]->PrevPtr = nullptr;
used.SetMax(1 << (numLevels));
for (int i = 1; i < MaxLevels; i++)
{
freeList[i] = nullptr;
}
}
int MemoryPool::AllocBlock(int level)
{
if (level < 0)
return -1;
if (freeList[level] == nullptr)
{
auto largeBlockAddr = AllocBlock(level - 1);
if (largeBlockAddr != -1)
{
auto block1 = (FreeListNode*)(buffer + ((largeBlockAddr ^ (1 << (numLevels - level))) << log2BlockSize));
block1->NextPtr = nullptr;
block1->PrevPtr = nullptr;
freeList[level] = block1;
int blockIndex = (1 << level) + (largeBlockAddr >> (numLevels-level)) - 1;
used.Add(blockIndex);
return largeBlockAddr;
}
else
return -1;
}
else
{
auto node = freeList[level];
if (node->NextPtr)
{
node->NextPtr->PrevPtr = node->PrevPtr;
}
freeList[level] = freeList[level]->NextPtr;
int rs = (int)((unsigned char *)node - buffer) >> log2BlockSize;
int blockIndex = (1 << level) + (rs >> (numLevels - level)) - 1;
used.Add(blockIndex);
return rs;
}
}
unsigned char * MemoryPool::Alloc(int size)
{
if (size == 0)
return nullptr;
int originalSize = size;
if (size < blockSize)
size = blockSize;
int order = numLevels - (Math::Log2Ceil(size) - log2BlockSize);
assert(order >= 0 && order < MaxLevels);
bytesAllocated += (1 << ((numLevels-order) + log2BlockSize));
bytesWasted += (1 << ((numLevels - order) + log2BlockSize)) - originalSize;
int blockId = AllocBlock(order);
if (blockId != -1)
return buffer + (blockId << log2BlockSize);
else
return nullptr;
}
void MemoryPool::FreeBlock(unsigned char * ptr, int level)
{
int indexInLevel = (int)(ptr - buffer) >> (numLevels - level + log2BlockSize);
int blockIndex = (1 << level) + indexInLevel - 1;
assert(used.Contains(blockIndex));
int buddyIndex = (blockIndex & 1) ? blockIndex + 1 : blockIndex - 1;
used.Remove(blockIndex);
if (level > 0 && !used.Contains(buddyIndex))
{
auto buddyPtr = (FreeListNode *)(buffer + ((((int)(ptr - buffer) >> log2BlockSize) ^ (1 << (numLevels - level))) << log2BlockSize));
if (buddyPtr->PrevPtr)
{
buddyPtr->PrevPtr->NextPtr = buddyPtr->NextPtr;
}
if (buddyPtr->NextPtr)
{
buddyPtr->NextPtr->PrevPtr = buddyPtr->PrevPtr;
}
if (freeList[level] == buddyPtr)
{
freeList[level] = buddyPtr->NextPtr;
}
// recursively free parent blocks
auto parentPtr = Math::Min(buddyPtr, (FreeListNode*)ptr);
if (level > 0)
FreeBlock((unsigned char*)parentPtr, level - 1);
}
else
{
// insert to freelist
auto freeNode = (FreeListNode *)ptr;
freeNode->NextPtr = freeList[level];
freeNode->PrevPtr = nullptr;
if (freeList[level])
freeList[level]->PrevPtr = freeNode;
freeList[level] = freeNode;
}
}
void MemoryPool::Free(unsigned char * ptr, int size)
{
if (size == 0)
return;
int originalSize = size;
if (size < blockSize)
size = blockSize;
int level = numLevels - (Math::Log2Ceil(size) - log2BlockSize);
bytesAllocated -= (1 << ((numLevels-level) + log2BlockSize));
bytesWasted -= (1 << ((numLevels - level) + log2BlockSize)) - originalSize;
FreeBlock(ptr, level);
}
}
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