jiangshun.txt

页面置换算法 是我的操作系统课程设计 只有代码

#include <iostream.h>

#define Bsize 3
#define Psize 20

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

class PRA
{
public:
     PRA(void);
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
void FIFO(void);//FIFO算法
void LRU(void);//LRU算法
void Optimal(void);//OPTIMAL算法
void BlockClear(void);//BLOCK恢复
pageInfor * block;//物理块
pageInfor * page;//页面号串

private:

};

PRA::PRA(void)
{
int QString[20]={7,0,1,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0,1};

     block = new pageInfor[Bsize];
for(int 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 PRA::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 PRA::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 PRA::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 PRA::display(void)
{


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


void PRA::Optimal(void)
{
int exist,space,position ;

for(int i=0; i<Psize; i++)
{    
   exist = findExist(i);
   if(exist != -1)
   { cout<<"不缺页"<<endl; }
   else
   {   
    space = findSpace();
    if(space != -1)
    {
     block[space] = page[i];  
     display();
    }
    else
    {
      for(int k=0; k<Bsize; k++)
     for(int j=i; j<Psize; j++)
     {
      if(block[k].content != page[j].content)
      { block[k].timer = 1000; }//将来不会用，设置TIMER为一个很大数
      else
      {
       block[k].timer = j;
       break;
      }
     }
     position = findReplace();   
     block[position] = page[i];   
     display();
    }
   }
}
}


void PRA::LRU(void)
{
int exist,space,position ;

for(int i=0; i<Psize; i++)
{
   exist = findExist(i);
   if(exist != -1)
   {
        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++;
}
}


void PRA::FIFO(void)
{

int exist,space,position ;

for(int i=0; i<Psize; i++)
{
   exist = findExist(i);
   if(exist != -1)
    {cout<<"不缺页"<<endl;}

   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++;//BLOCK中所有页面TIMER++
}
}

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


void main(void)
{
cout<<"|----------页 面 置 换 算 法----------|"<<endl;
cout<<"|---power by zhanjiantao(028054115)---|"<<endl;
cout<<"|-------------------------------------|"<<endl; 
cout<<"页面号引用串:7,0,1,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0,1"<<endl;
cout<<"----------------------------------------------------"<<endl;
cout<<"选择<1>应用Optimal算法"<<endl;
cout<<"选择<2>应用FIFO算法"<<endl;
cout<<"选择<3>应用LRU算法"<<endl;
cout<<"选择<0>退出"<<endl;
int select;
PRA test;


while(select)
{
   cin>>select;
   switch(select)
   {
    case 0:
     break;
    case 1:
     cout<<"Optimal算法结果如下:"<<endl;
     test.Optimal();
     test.BlockClear();
     cout<<"----------------------"<<endl;
     break;
    case 2:
     cout<<"FIFO算法结果如下:"<<endl;
     test.FIFO();
     test.BlockClear();
     cout<<"----------------------"<<endl;
     break;
    case 3: 
     cout<<"LRU算法结果如下:"<<endl;
     test.LRU();
     test.BlockClear();
     cout<<"----------------------"<<endl;
     break;
    default:
     cout<<"请输入正确功能号"<<endl;
     break;
   }
  
}

}