c++ 内存池技术实现

#include"MemoryPool.h" MemoryPool::MemoryBlock::MemoryBlock(USHORT nTypes , USHORT nUnitSize ) { this->nSize=nTypes*nUnitSize; nFree=nTypes; nFirst=0; pNext=NULL; { char * pData = aData; for (USHORT i = 1; i < nTypes; i++) { *reinterpret_cast<USHORT*>(pData) = i; pData += nUnitSize; } } } MemoryPool::MemoryPool(USHORT unitSize,USHORT initSize,USHORT growSize) { this->initSize=initSize; this->growSize=growSize; if(unitSize<=2) { this->unitSize=2; } else if(unitSize>4) { this->unitSize = (unitSize + (MEMORY_ALLGNMENT-1)) & ~(MEMORY_ALLGNMENT-1); } else { this->unitSize=4; } pBlock=NULL; blockNum=0; } void* MemoryPool::alloc() { if(!pBlock) { pBlock=new(initSize,unitSize)MemoryBlock(initSize,unitSize); blockNum++; } MemoryBlock* pMyBlock = pBlock; while (pMyBlock && !pMyBlock->nFree ) { pMyBlock = pMyBlock->pNext;//寻找空闲内存块 } if(pMyBlock) { char* pFree=(pMyBlock->aData+pMyBlock->nFirst*unitSize);//返回空闲地址 pMyBlock->nFree--; pMyBlock->nFirst=*((USHORT*)pFree); return static_cast<void*>(pFree); } else { if ( !growSize ) return NULL; pMyBlock = new(growSize,unitSize)MemoryBlock(growSize,unitSize);;//扩展新的内存块 blockNum++; pMyBlock->pNext = pBlock; pBlock = pMyBlock; pMyBlock->nFree--; pMyBlock->nFirst=1; return static_cast<void*>(pMyBlock->aData); } } void MemoryPool::free(void* pFree) { MemoryBlock* pMyBlock = pBlock; while ( ((ULONG)pMyBlock->aData > (ULONG)pFree) || ((ULONG)pFree >= ((ULONG)pMyBlock->aData + pMyBlock->nSize)) )//判断内存地址是否在内存池内 { pMyBlock=pMyBlock->pNext; } if(!pMyBlock) return; pMyBlock->nFree++; *((USHORT*)pFree) = pMyBlock->nFirst; pMyBlock->nFirst = (USHORT)(((ULONG)pFree-(ULONG)(pBlock->aData)) / unitSize);//修改链表结构 if(pMyBlock->nFree*unitSize==pMyBlock->nSize)//内存块完全空闲 { if(pBlock==pMyBlock) { pBlock=pMyBlock->pNext; MemoryBlock::operator delete(pMyBlock,0);//空闲块在头部 blockNum--; } else //空闲块在链表中部 { MemoryBlock* pTemp=pBlock; while(pTemp->pNext!=pMyBlock) { pTemp=pTemp->pNext; } pTemp->pNext=pMyBlock->pNext; MemoryBlock::operator delete(pMyBlock,0); blockNum--; } } } MemoryPool::~MemoryPool() { MemoryBlock* pMyBlock=pBlock; while(pBlock) { pMyBlock=pBlock; pBlock=pMyBlock->pNext; MemoryBlock::operator delete(pMyBlock,0); } }