memory pool(記憶體池)的模板實現（暫不支援多線程）

MemoryPool代碼：

 #include <Windows.h><br />#include <cassert></p><p>template <typename T, int ALLOC_BLOCK_SIZE = 50><br />class MemoryPool<br />{<br />public:<br /> MemoryPool(void)<br /> {<br /> };<br /> virtual ~MemoryPool(void)<br /> {<br /> };<br /> static VOID* operator new(size_t allocLength)<br /> {<br /> assert(sizeof(T) >= sizeof(UCHAR*));<br /> assert(sizeof(T) == allocLength);<br /> /////沒可用的block就重新分配<br /> if(!freePtr)<br /> {<br /> allocBlock();<br /> }<br /> /////分配當前可用塊freePtr給申請者，同時freePtr指向下一個可用的block<br /> UCHAR* forreturn = freePtr;<br /> freePtr = *reinterpret_cast<UCHAR**>(forreturn);<br /> return forreturn;<br /> };<br /> static VOID operator delete(VOID* deletePtr)<br /> {<br /> /////deletePtr的下一個可用block指向freePtr，然後freePtr指向deletePtr<br /> *reinterpret_cast<UCHAR**>(deletePtr) = freePtr;<br /> freePtr = static_cast<UCHAR*>(deletePtr);<br /> };<br />private:<br /> /////alloc一定數量的記憶體block,然後將其串起來作為可用的block鏈<br /> /////不過串的方式比較特殊，它是通過向每個block的前4(sizeof(UCHAR*))個<br /> /////位元組裡寫入下一個可用block塊的起始地址來串起來的。<br /> static void allocBlock()<br /> {<br /> freePtr = new UCHAR[sizeof(T) * ALLOC_BLOCK_SIZE];<br /> UCHAR** forassign = reinterpret_cast<UCHAR**>(freePtr);<br /> UCHAR* curPtr = freePtr;<br /> for(int i = 0; i < ALLOC_BLOCK_SIZE - 1; i++)<br /> {<br /> curPtr += sizeof(T);<br /> *forassign = curPtr;<br /> forassign = reinterpret_cast<UCHAR**>(curPtr);<br /> }<br /> *forassign = 0;<br /> };<br />private:<br /> static UCHAR* freePtr;<br />};</p><p>template <typename T, int ALLOC_BLOCK_SIZE><br />UCHAR* MemoryPool<T, ALLOC_BLOCK_SIZE>::freePtr = NULL;

 

 

效能測試代碼：

#include <Windows.h><br />#include <iostream><br />#include "MemoryPool.h"<br />#include <time.h></p><p>using namespace std;</p><p>class A : public MemoryPool<A><br />{<br />private:<br /> BYTE a[1024];<br /> BYTE b[1025];<br />};</p><p>class B<br />{<br />private:<br /> BYTE a[1024];<br /> BYTE b[1024];<br />};</p><p>int _tmain(int argc, _TCHAR* argv[])<br />{<br /> clock_t start, finish;<br /> start = clock();<br /> for(int i= 0; i < 2000000; i++)<br /> {<br /> A* pa = new A();<br /> delete pa;<br /> }<br /> finish = clock();<br /> cout<<"use memory pool : elapsed "<<(finish - start)<<"ms"<<endl;</p><p> start = clock();<br /> for(int i= 0; i < 2000000; i++)<br /> {<br /> B* pb = new B();<br /> delete pb;<br /> }<br /> finish = clock();<br /> cout<<"not use : elapsed "<<(finish - start)<<"ms"<<endl;</p><p> system("pause");</p><p>return 0;<br />}

 

 

測試結果：