LRU算法

#include <stdio.h>
#include <stdlib.h>
#include <iostream.h>
#include <time.h>
 

#define Bsize 3
#define Psize 20

struct pageInfor
{
	int content;//页面号
	int timer;//被访问标记
};

class LRU
{
	public:
		LRU(int qstring[]);
		int findSpace(void);//查找是否有空闲内存
		int findExist(int curpage);//查找内存中是否有该页面
		int findReplace(void);//查找应予置换的页面
		void display(void);//显示
		int  LRUpro(void);//LRU算法
		void BlockClear(void);//BLOCK恢复
		pageInfor * block;//物理块
		pageInfor * page;//页面号串
};

LRU::LRU(int qstring[])
{
	int i;
	block = new pageInfor[Bsize];
	for(i=0; i<Bsize; i++)
	{
		block[i].content = -1;
		block[i].timer = 0;
	}

	page = new pageInfor[Psize];
	for(i=0; i<Psize; i++)
	{
		page[i].content = qstring[i];
		page[i].timer = 0;
	}
}


int LRU::findSpace(void)
{
	for(int i=0; i<Bsize; i++)
		if(block[i].content == -1)
			return i;//找到空闲内存，返回BLOCK中位置
	return -1;
}

int LRU::findExist(int curpage)
{

	for(int i=0; i<Bsize; i++)
		if(block[i].content == page[curpage].content)
			return i;//找到内存中有该页面，返回BLOCK中位置
	return -1;
}

int LRU::findReplace(void)
{
	int pos = 0;

	for(int i=0; i<Bsize; i++)
	if(block[i].timer >= block[pos].timer)
		pos = i;//找到应予置换页面，返回BLOCK中位置
	return pos;
}

void LRU::display(void)
{
	for(int i=0; i<Bsize; i++)
	if(block[i].content != -1)
		cout<<block[i].content<<" ";
	cout<<endl;
}

void LRU::BlockClear(void)
{
	for(int i=0; i<Bsize; i++)
	{
		block[i].content = -1;
		block[i].timer = 0;
	}
}


int LRU::LRUpro(void)
{
	int exist,space,position ;
	int noscarBsize=0;

	for(int i=0; i<Psize; i++)
	{
		exist = findExist(i);
		if(exist != -1)
		{
			noscarBsize++;
			cout<<"不缺页"<<endl;
			block[exist].timer = -1;//恢复存在的并刚访问过的BLOCK中页面TIMER为-1
		}
  		else
  		{
   			space = findSpace();
   			if(space != -1)
   			{
    			block[space] = page[i];
    			display();
   			}
   			else
   			{
    			position = findReplace();
    			block[position] = page[i];  
    			display();
   			}
  		}
  		for(int j=0; j<Bsize; j++)
   			block[j].timer++;
 	}
	return noscarBsize;
}

/*在linux下用gcc编译时，使用gcc lru3.cpp -lstdc++*/ 


int main(void)
{
	cout<<"|----------页 面 置 换算法----------|"<<endl;
	cout<<"|---please seect:---|"<<endl;
	cout<<"|-----1:LRU--------|"<<endl;
	cout<<"|-------0 :exit------|"<<endl;
 	cout<<"|-------------------------------------|"<<endl;
 
 	int select;
	int i,scarBsize=0;
	float f;
	int qstring[20];
 
 	while(select)
 	{
  		cin>>select;
  		switch(select)
  		{
   			case 0:
    			break;
   			case 1:
   			{
			   	
				cout<<"the amount of page block is 3:"<<endl;
				cout<<"produce the sequence of 20 length randomly:"<<endl ;
				srand((unsigned)time(NULL));
				for(i=0;i<Psize;i++)
				{
					if(!(i%10))
		 				cout<<endl;
						qstring[i]= rand() % 8;
						cout<<"*"<<qstring[i];
				}
    			cout<<endl;
				LRU test(qstring);
				cout<<"the result of LRU algorithm is"<<endl;
				scarBsize=20-test.LRUpro();
				cout<<"the amout of scarpage is"<<scarBsize<<endl;
				f=scarBsize/20.0;
				cout<<"the ratio of the  is"<<f<<endl;
    			test.BlockClear();
    			cout<<"----------------------"<<endl;
				break;
  			}	
   			default:
    			cout<<"请输入正确功能号"<<endl;
    			break;
  		}
 	}
 	return 0;
}