利用内存chunk充当数据buffer的stack的一个简单实现

问题描述：

1.stack是计算机中最常用到的数据结构，它主要依据支持后进先出(LIFO)操作抽象而出的一种数据结构；

      2.本文尝试自己封装一个泛型的stack class，它支持常见的操作；

      3.这个类的底层的数据存储容器是以单链表串起来的内存块（memory chunk ）实现，这样做主要是为了性能的考量；

      4.有个小技巧预先分配一个内存块和这个链表没关联，当stack存储非常少量的东西时，都不用启用链表机制；

      5.最后我又封装一个底层容器为stl的stack class,这主要是为了性能比较的考虑；

      6.最后我分别比较了以下四种情形的性能：

 1）stack class (data container = memory chunk)

         2)  stack class (data container =list )

         3)  stack class (data container = vector )

         4)  st::stack

         结论是1最好，3是1的2倍，4比1差一些，2性能非常差；

程序代码：

#ifndef _ALSTACK_H_#define _ALSTACK_H_#include <list>#include <vector>#include <stack>#include "windows.h"/** The class encapsulate simple stack operation* under interface, it's buffer is made of memory chunk* compare with array and list in under buffer, it improve performance * **/template<class T>class AlStack{public:AlStack():m_totalCount(0), m_count(0){m_dataBuffer = &m_initBuffer;}~AlStack(){Clear();}void Clear(){while( m_dataBuffer != &m_initBuffer ){Buffer* buf = m_dataBuffer;m_dataBuffer = m_dataBuffer->next;delete buf;}}int Count(){return m_totalCount;}bool IsEmpty(){return m_totalCount == 0;}void Push( T& rhs ){*Push() = rhs;}T& At( int index ){assert( index >= 0 && index < m_count );return m_dataBuffer->buf[m_count - index - 1];}const T& At( int index ) const {assert( index >= 0 && index < m_count );return m_dataBuffer->buf[m_count - index - 1];}T& Top(){assert( m_dataBuffer && m_count > 0 );return m_dataBuffer->buf[m_count - 1];}const T& Top() const{assert( m_dataBuffer && m_count );return m_dataBuffer->buf[m_count - 1];}void Pop( T& item ){item = Top();Pop();}void Pop(){m_totalCount--;if( --m_count == 0 ){if( m_dataBuffer != &m_initBuffer ){Buffer* buf = m_dataBuffer;m_dataBuffer = m_dataBuffer->next;delete buf;buf = 0;// reset the value of m_countm_count = KSlotCount;}}}private:AlStack( const AlStack& rhs ){}AlStack& operator = ( const AlStack& rhs ){}T* Push(){if( KSlotCount == m_count ){Buffer* buf = new Buffer;assert( buf );buf->next = m_dataBuffer;m_dataBuffer = buf;//reset the value of value in single bufferm_count = 0;}m_totalCount++;return &m_dataBuffer->buf[m_count++];}private:enum {KSlotCount = 64};int m_totalCount;int m_count;struct Buffer{T        buf[KSlotCount];Buffer*  next;Buffer():next(0){memset( buf, 0x00, sizeof(buf) );}};Buffer     m_initBuffer;Buffer*    m_dataBuffer;};/** The stack implement it's operation by terms of stl container* */template<class T, class V = std::list<T> >class StackList{public:StackList():m_dataBuffer(){}~StackList(){Clear();}void Clear(){m_dataBuffer.clear();}int Count(){return m_dataBuffer.size();}bool IsEmpty(){return m_dataBuffer.size() == 0;}void Push( T& rhs ){m_dataBuffer.push_back(rhs);}T& Top(){assert( m_dataBuffer.size());return m_dataBuffer.back();}const T& Top() const{assert( m_dataBuffer.size());return m_dataBuffer.back();}void Pop( T& item ){item = m_dataBuffer.back();Pop();}void Pop(){m_dataBuffer.pop_back();}private:StackList( const StackList& rhs ){}StackList& operator = ( const StackList& rhs ){}private:V  m_dataBuffer;};/** Test interface**/template<class T>void UnitTestPerformance( T& stackObj, const char* strName ){unsigned long start = GetTickCount();const int len = 640000;stackObj;for( int i = 0; i < len; i++ ){stackObj.Push( i );}for( int i = 0; i < len; i++ ){int res = stackObj.Top();stackObj.Pop();assert( res == len - i - 1 );}assert( stackObj.IsEmpty() == true );unsigned long interval = GetTickCount() - start;printf( "%s consume time is %d \n", strName, interval );} void StackPerformance( std::stack<int>& stackObj, const char* strName){unsigned long start = GetTickCount();const int len = 640000;stackObj;for( int i = 0; i < len; i++ ){stackObj.push( i );}for( int i = 0; i < len; i++ ){int res = stackObj.top();stackObj.pop();assert( res == len - i - 1 );}unsigned long interval = GetTickCount() - start;printf( "%s consume time is %d \n", strName, interval );}/** Performance compare **/void TestAlStack(){AlStack<int> stackObj;UnitTestPerformance( stackObj, " the stack of memory chunk" );StackList<int> stackListObj;UnitTestPerformance( stackListObj, " the stack of stl list " );StackList<int, std::vector<int> > stackVecObj;UnitTestPerformance( stackVecObj, " the stack of stl vector " );std::stack<int> stackStlObj;StackPerformance( stackStlObj, " the stack of stl " );}#endif 

compile and run in visual studio 2005

test result as follows: