优先数处理机调度

//用位示图管理磁盘存储空间
#include <iostream.h>
struct mapping //页号与块号对应 
{
    int page; //页号 
    int mass; //块号 
    struct mapping *next; 
}; 
struct pagelist 
{
    int length; //页表长度 
    mapping *map;  
}; 
struct request
{
    int num; //进程号 
    int size; //请求页面数
    pagelist *plist; //页表始址
    int length; //页表长度
    char state;  //状态,Y表示已分配，N表示未分配 
    struct request *next;
};
request *S; //请求表 
static int a[8][8];
void allot();
void back();
void reallot(); 
void display(); 
int main()
{
    S=new request;
    S->next=NULL; 
    int a;
    cout<<"              用位示图管理磁盘存储空间"<<endl; 
    cout<<"1:分配磁盘"<<endl; 
    cout<<"2:回收磁盘"<<endl; 
    cout<<"0:退出"<<endl;    
    while(1)
    {
        cout<<endl<<"请按键选择：";
        cin>>a;
        if(a>2||a<0)
        {
            cout<<endl<<"输入错误，请重新输入："; 
            continue;
        }
        switch(a)
        {
            case 1: allot(); display(); break;
            case 2: back();  display(); break;
            case 0: goto end; 
        } 
    } 
    end: 
    getchar();
    getchar();
}
void allot()
{
    int i,j,m=0; 
    request *r=S,*p=new request;
    p->next=NULL; 
    cout<<"请输入进程号和申请的空间大小："<<endl;
    cin>>p->num>>p->size;
    if(p->size<=0)
    {
        cout<<"申请空间大小错误."<<endl;
        delete p;
        return;
    }      
    while(r->next!=NULL) //将p插到请求链表表尾 
        r=r->next;
    r->next=p;    
    for(i=0;i<8;i++)   //检查磁盘空间大小 
    {
       for(j=0;j<8;j++)
         if(a[i][j]==0)  m++;
    }
    if(m<p->size)  //磁盘空间不够时 
    {
        cout<<endl<<"磁盘空间不够."<<endl;
        p->length=0;
        p->state='N';
        p->plist=0; 
        return;
    }   //磁盘空间够时 
    m=0; 
    p->length=p->size; 
    p->state='Y'; 
    p->plist=new pagelist;  //建立页表 
    p->plist->length=p->length;
    p->plist->map=new mapping;  //建立页表与物理块的对应关系
    p->plist->map->next=NULL; 
    mapping *t=p->plist->map; 
    cout<<"\t柱面号\t磁道号\t物理记录号"<<endl; 
    for(i=0;i<8;i++)
    {
       for(j=0;j<8;j++) 
         if(a[i][j]==0)
         {   
             a[i][j]=1;
             m++;
             mapping *q=new mapping;
             q->next=NULL; 
             q->page=m-1;
             q->mass=i*8+j;
             cout<<"第"<<m<<"块：";
             cout<<"\t"<<i;
             cout<<"\t"<<j/4;
             cout<<"\t"<<j%4<<endl;              
             while(t->next!=NULL)  //插到物理块与页号对应关系链表的表尾 
                t=t->next;
             t->next=q;
             q->next=NULL;    
             if(m==p->size)    goto end;
         }  
    } 
    end:
    cout<<"分配成功."<<endl<<endl;    
} 
void back()
{
    int b; 
    cout<<"请输入要回收磁盘空间的进程号："<<endl;
    cin>>b;
    request *p=S->next;
    while(p!=NULL&&p->num!=b)
       p=p->next;
    if(p==NULL)
    {
        cout<<endl<<"此进程不存在."<<endl;  
        return;
    }
    if(p->state=='N')
    {
        cout<<endl<<"错误,此进程没有占据磁盘空间."<<endl;
        return;
    }
    cout<<endl<<"共回收"<<p->size<<"个物理块空间,具体情况如下:"<<endl;
    int i,j;
    cout<<endl<<"  每块字节号  位数号"<<endl;
    mapping *q=p->plist->map->next;
    for(int k=0;k<p->size;k++)
    {
        i=q->mass/8;
        j=q->mass%8;
        a[i][j]=0; 
        cout<<"\t"<<i<<"\t"<<j<<endl;
        mapping *t;
        p->plist->map->next=q->next;
        t=q;
        q=p->plist->map->next; 
        delete t;
    }     
    if(S->next==p)
       S->next=p->next;
    else
    {
        request *r=S;
        while(r->next!=p)
          r=r->next;
        r->next=p->next;  
    }           
    delete p->plist->map;
    delete p->plist;
    delete p;  
    reallot();  
}
void reallot()
{
    int m=0;
    request *r=S,*p=new request;
    p->next=NULL;  
    while(r->next!=NULL)
    {
        p=r->next;
        r=r->next; 
        if(p->state=='N')  //如果存在等待分配内存的进程 
        { 
            for(int i=0;i<8;i++)   //检查磁盘空间大小 
            {
               for(int j=0;j<8;j++)
               if(a[i][j]==0)  m++;
            } 
            if(m<p->size)  //内存仍不够 
            {  m=0;   continue;} 
            else
            {   
                cout<<endl<<"进程"<<p->num<<"分配情况如下："<<endl; 
                m=0; 
                p->length=p->size; 
                p->state='Y'; 
                p->plist=new pagelist;  //建立页表 
                p->plist->length=p->length;
                p->plist->map=new mapping;  //建立页表与物理块的对应关系
                p->plist->map->next=NULL; 
                mapping *t=p->plist->map; 
                cout<<"\t柱面号\t磁道号\t物理记录号"<<endl; 
                for(int i=0;i<8;i++)
                {
                   for(int j=0;j<8;j++) 
                   if(a[i][j]==0)
                   {   
                      a[i][j]=1;
                      m++;
                      mapping *q=new mapping;
                      q->next=NULL; 
                      q->page=m-1;
                      q->mass=i*8+j;
                      cout<<"第"<<m<<"块：";
                      cout<<"\t"<<i;
                      cout<<"\t"<<j/4;
                      cout<<"\t"<<j%4<<endl;              
                      while(t->next!=NULL)  //插到物理块与页号对应关系链表的表尾 
                        t=t->next;
                      t->next=q;
                      q->next=NULL;    
                      if(m==p->size)  {m=0;  goto end;} 
                   }  
                } 
                end:
                      cout<<"分配成功."<<endl<<endl;  
             } 
        } 
    }
} 
void display()
{
    request *p=S->next;
    cout<<"进程号\t请求页面数\t页表地址\t页表长度\t状态"<<endl;
    while(p!=NULL)
    {
        if(p->state=='N') 
          cout<<p->num<<"\t"<<p->size<<"\t\t"<<p->plist<<"\t\t"<<p->length<<"\t\t"<<p->state<<endl;
        else  
          cout<<p->num<<"\t"<<p->size<<"\t\t"<<p->plist<<"\t"<<p->length<<"\t\t"<<p->state<<endl; 
        p=p->next;
    }
    cout<<endl; 
    for(int i=0;i<8;i++)
    {
       for(int j=0;j<8;j++)
          cout<<"    "<<a[i][j]; 
       cout<<endl;
    }
}