内存池实现示例

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1.模板类定义（使用了模板以适应不同对象的内存需求，内存池中的内存块则是以基于链表的结构进行组织）

<pre name="code" class="cpp">#include <QApplication>#include <new>#include <assert.h>#include <QDebug>template <class T, int BLOCK_NUM= 50>class MemPool{public:    static void *operator new(size_t allocLen)    {        assert(sizeof(T) == allocLen);        qDebug()<<"allocLen = "<<allocLen;        if(!m_NewPointer)            MemAlloc();        unsigned char *rp = m_NewPointer;        m_NewPointer = *reinterpret_cast<unsigned char**>(rp); //由于头4个字节被“强行”解释为指向下一内存块的指针，这里m_NewPointer就指向了下一个内存块，以备下次分配使用。        return rp;    }    static void operator delete(void *dp)    {        *reinterpret_cast<unsigned char**>(dp) = m_NewPointer;        m_NewPointer = static_cast<unsigned char*>(dp);        qDebug()<<"memDelete";    }private:    static void MemAlloc()    {        m_NewPointer = new unsigned char[sizeof(T) * BLOCK_NUM];        unsigned char **cur = reinterpret_cast<unsigned char**>(m_NewPointer); //强制转型为双指针，这将改变每个内存块头4个字节的含义。        unsigned char *next = m_NewPointer;        for(int i = 0; i < BLOCK_NUM-1; i++)        {            next += sizeof(T);            *cur = next;            cur = reinterpret_cast<unsigned char**>(next); //这样，所分配的每个内存块的头4个字节就被“强行“解释为指向下一个内存块的指针， 即形成了内存块的链表结构。        }        *cur = 0;        qDebug()<<"memAlloc";    }    static unsigned char *m_NewPointer;protected:    ~MemPool(){}};template<class T, int BLOCK_NUM >unsigned char *MemPool<T, BLOCK_NUM >::m_NewPointer;

2.模板类的应用

class ExpMP : public MemPool<ExpMP>{    char a[1024];};int main(int argc, char *argv[]){    QApplication a(argc, argv);    ExpMP *aMP = new ExpMP();    delete aMP;    return a.exec();}

运行结果为：

allocLen =  1024 memAlloc memDelete

参考文献：百度百科之内存池篇。。。

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