C++内存池实现

class Airplane{
private:
    struct AirpRef {
        unsigned long miles;
        char type;
    };
private:
    union {
        AirpRef rep;
        Airplane *next;
    };
public:
    static void *operator new(size_t sizes) {
        if(sizes != sizeof(Airplane)) return ::operator new(sizes);

        Airplane *p = headOfFreeList;//得到一块内存
        if(p) headOfFreeList = p->next;//如果有效
        else {
            //empty
            Airplane* newBlock = static_cast<Airplane*>(::operator new(block_size * sizeof(Airplane)));

            for(int i = 1; i < block_size - 1; ++i) {
                newBlock[i].next = &newBlock[i + 1];
            }
            newBlock[block_size - 1].next = 0;
            p = newBlock;
            headOfFreeList = &newBlock[1];
        }
        return p;
    }
    static void operator delete(void *p,size_t sizes) {
        if(p == 0) return;
        if(sizes != sizeof(Airplane)) {
            ::operator delete(p);
            return;
        }
        Airplane * carcass = static_cast<Airplane*>(p);
        carcass->next = headOfFreeList;
        headOfFreeList = carcass;
    }

private:
    static const int block_size;
    static Airplane* headOfFreeList;
};

const int Airplane::block_size = 512;
Airplane* Airplane::headOfFreeList;

    const int N = 100;
    Airplane *p[N],*p2[N];
    for(int i = 0; i < N; i++) {
        p[i] = new Airplane;
        p2[i] = reinterpret_cast<Airplane*>(malloc(sizeof(Airplane)));
    }

    for(int i = 0; i < 5; i++) {
        cout<<p[i]<<endl;
    }
    cout<<endl;
    for(int i = 0; i < 5; i++) {
        cout<<p2[i]<<endl;
    }    
    return 0;

测试结果：

前五个使用的内存池，每个元素之间相隔是8，而用原生的malloc则相隔0x40（64），可见内存池在节省内存方面的优秀。