某内存池中的指针用法

内存池实现有许多种，各有不同的优缺点。

这里不是主要说内存池，只是觉得这个内存池中的指针用得很飘逸！

template <class T,int AllocSize = 50>class MemPool{public:static void* operator new(size_t allocLength){if(!mStartPotinter){MyAlloc();}//将当前指向空闲内存起始地址作为反回地址unsigned char* p = mStartPotinter;//取出空闲区域前4字节的值，赋值给空闲地址//因为前四字节中存放了下一个BLOCK的地址mStartPotinter = *(unsigned char**)mStartPotinter;return p;}static void operator delete(void* deleteP){//assert(deletePointer);*(unsigned char**)deleteP = mStartPotinter;mStartPotinter = (unsigned char*)deleteP;}static void MyAlloc(){//预分配内存mStartPotinter = new unsigned char[sizeof(T)*AllocSize];//构造BLOCK之间的关系 //每个BLOCK的前4BYTE存放了下一个BLOCK的地址unsigned char** next = (unsigned char**)mStartPotinter;unsigned char* p = mStartPotinter;for(int i = 0; i< AllocSize;++i){p +=sizeof(T);//步进*next = p;//赋值next = (unsigned char**)p;//步进}*next = NULL;}static unsigned char* mStartPotinter;};template <class T,int AllocSize>unsigned char* MemPool<T,AllocSize>::mStartPotinter = NULL;

简单提示一下： unsigned char** next = (unsigned char**)mStartPotinter;

mStartPotinter作为二维指针的时候，相当于是一系列的unsigned char* [].

对于第一个 *next 相当于(unsigned char*)mStartPointer[0].

第二个相当于(unsigned char*)mStartPointer[sizeof(T)*1];

第三个相当于(unsigned char*)mStartPointer[sizeof(T)*2];

所以，构造BLOCK之间关系的时候，也可以写成

for(int i = 0; i< AllocSize;++i) { p +=sizeof(T);//步进 unsigned char* pp = (unsigned char*)(p[sizeof(T)*i]); pp = p;//赋值 }

不想多解释了，累。估计多看几分种啥都明白了！