//下面的代码思想取自efficient c++
 1 ////////////////////////////////////////////////////////////////////////// 2 //可分为：1.内存池本身的创建和删除 3 //        2.内存池中空闲内存的维护 4 //两个部分区分开，逻辑就清晰了。 5 //by wangpei 2015.1.4 6 ///////////////////////////////////////////////////////////////////////// 7 template <typename T> 8 class MemoryPool{ 9 public:10     MemoryPool(size_t size = EXSIZE);11     ~MemoryPool();12     inline void* alloca(size_t size);13     inline void free(void *element);14 private:15     enum {EXSIZE = 32};16     MemoryPool<T> *next;17     void expand(size_t s = EXSIZE);18 };19 template<typename T>20 MemoryPool<T>::MemoryPool(size_t size)21 {22     expand(size);23 }24 25 template<typename T>26 MemoryPool<T>::~MemoryPool()27 {28     MemoryPool<T> * ptr;29     while (next){30        ptr = next->next;31        delete[] freeNode; //指针指向了正确的初始位置，就能够正确的释放空间32        de++;33        next = ptr;34     }35 }36 37 template<typename T>38 inline void* MemoryPool<T>::alloca(size_t size)39 {40     if (next == 0)41        expland();42     MemoryPool<T>* currentFree = next;43     next = next->next;44     return currentFree;45 }46 47 template<typename T>48 inline void MemoryPool<T>::free(void *element)49 {50     MemoryPool<T>* head = static_cast<MemoryPool<T>* >(doomed); //注意此处的链表维护，不能让链表断开了51     head->next = next;52     next = head;53 }54 55 template<typename T>56 void MemoryPool<T>::expand(size_t s)57 {58     const size_t s = (sizeof(MemoryPool<T>*) >= sizeof(T)) ? sizeof(MemoryPool<T>*) : sizeof(T);//这里是关键，根据类型的大小确定堆大小59     MemoryPool<T>* head = (MemoryPool<T>*)new char[s];  //将char*强制转换为MemoryPool<T>* 可读性很差，但却高效的利用了内存空间60     ma++;61     head->next = next;62     freeNode = head;63     for (size_t i = 0; i < EXPANSION; i++){64        head = (MemoryPool<T>*)new char[s];65        ma++;66        head->next = next;67        next = head;68     }69 }70 class Rational_tem{71 private:72     static MemoryPool<Rational_tem> * memPool;73     int n;74     int d;75 public:76     Rational_tem(int a = 0, int b = 1) :n(a), d(b){}77     void* operator new (size_t s)78     {79        return memPool->alloca(s); 80     }81     void operator delete(void* doomed, size_t s)82     {83        return memPool->free(doomed);84     }85     static void newMemPool()86     {87        memPool = new MemoryPool < Rational_tem > ;88     }89     static void deleteMemPool()90     {91        delete memPool;92     }93 };