B类增加了嵌入指针
#include<new>
#include<ctime>
#include<iostream>
#include<cstdio>
class A
{
public:A() {printf("next=%p\n", next);};static void* operator new(size_t size);static void operator delete(void* phead);static int m_iCount;// 用于分配计数统计，每new一次 + 1static int m_iMallocCount;A* next;//用于统计ma11oc次数，每ma11oc一次+1
private:static A* m_FreePosi;// 总是指向一块可以分配出去的内存的首地址static int m_sTrunkCount;//一次分配多少倍该类的内存
};void* A::operator new(size_t size)
{//A ppoint =(A *)malloc(size);//不再用传统方式实现，而是用内存池实现//return ppoint;A* tmplink;if (m_FreePosi == nullptr){//为空，我们要申请内存，申请的是很大一块内存size_t realsize = m_sTrunkCount * size;//申请m_sTrunkCount这么多倍的内存m_FreePosi = reinterpret_cast<A*>(new char[realsize]); // 这是传统new, 调用底层tmplink = m_FreePosi;//把分配出来的这一大块内存链接起来，供后续使用for (; tmplink != &m_FreePosi[m_sTrunkCount - 1]; ++tmplink){tmplink->next = tmplink + 1;printf("%p\n", tmplink->next);}tmplink->next = nullptr;++m_iMallocCount;}tmplink = m_FreePosi;m_FreePosi = m_FreePosi->next;++m_iCount;return tmplink;
}
void A :: operator delete(void* phead)
{//free(phead);//不再用传统方式实现，针对内存池有特别的实现(static_cast <A*>(phead))->next = m_FreePosi;m_FreePosi = static_cast <A*>(phead);
}
int A::m_iCount = 0;
int A::m_iMallocCount = 0;
A* A::m_FreePosi = nullptr;
int A::m_sTrunkCount = 5;class B
{
private:struct obj {unsigned long mile;char type;};union{obj b;B* next;};public:unsigned long getMiles() { return b.mile; }char getType() { return b.type; }void set(unsigned long m, char t) {b.mile = m;b.type = t;}static void* operator new(size_t size);static void operator delete(void* phead);static int m_iCount;// 用于分配计数统计，每new一次 + 1static int m_iMallocCount;//用于统计ma11oc次数，每ma11oc一次+1
private:static B* m_FreePosi;// 总是指向一块可以分配出去的内存的首地址static int m_sTrunkCount;//一次分配多少倍该类的内存
};void* B::operator new(size_t size)
{B* p = m_FreePosi;if (p) //如果p有效就把链表头部向下移m_FreePosi = p->next;else{//如果链表已空，申请一大块内存B* newBlock = static_cast<B*>(::operator new(m_sTrunkCount * sizeof(B)));//将小块穿成一个freelistfor (int i = 1; i < m_sTrunkCount - 1; ++i)newBlock[i].next = &newBlock[i + 1];newBlock[m_sTrunkCount - 1].next = 0;p = newBlock;m_FreePosi = &newBlock[1];}return p;
}void B :: operator delete(void* phead){//free(phead);//不再用传统方式实现，针对内存池有特别的实现(static_cast <B*>(phead))->next= m_FreePosi;m_FreePosi= static_cast <B*>(phead);}int B :: m_iCount =0;int B :: m_iMallocCount =0;B* B::m_FreePosi= nullptr;int B :: m_sTrunkCount =5;//一次分配5倍的该类内存作为内存池的大小class C{public:C();~C();private:};C::C(){}C::~C(){}int main8() {clock_t start, end,end2;start = clock();for (int i = 0; i < 5000000; ++i){B* pa = new B();//printf("%p\n", pa);//pa->set(i, i+'a');//std::cout << pa->getMiles() << pa->getType() << std::endl;}end = clock();for (int i = 0; i < 5000000; ++i){C* pa = new C();//printf("%p\n", pa);//pa->set(i, i+'a');//std::cout << pa->getMiles() << pa->getType() << std::endl;}end2 = clock();std::cout <<"使用内存池" << end - start << std::endl;std::cout << "不使用内存池" << end2 - end << std::endl;return 1;/*使用内存池322不使用内存池907*/}
