操作系统2.cpp

操作系统的一个小实验

#include<iostream>
#include<string>
using namespace std;

struct Block                  //空闲链结构体
{
string name;              //作业名
int address;              //分区首地址  
int size;                  //分区大小
int nowstate;                 //分区状态
struct Block *next;          //前向指针
struct Block *front;         //后向指针
};

struct Used                    //已分配分区结构体
{
  Block *usedArea;        
  Used *next;
};

Block *freeHead;         // 带表头附加节点的空闲链头指针
Used *usedHead;          //带表头附加结点的已分配分区头指针


void InitValue(void)     //初始化函数
{struct Block *p,*temp;
 freeHead=(struct Block *)malloc(sizeof(struct Block));
 freeHead->size=0;
 freeHead->next=NULL;
 freeHead->nowstate=1;
 usedHead=(struct Used *)malloc(sizeof(struct Used));
 p=(struct Block *)malloc(sizeof(struct Block));
 p->address=0;
 usedHead->usedArea=p;
 usedHead->next=NULL;
 temp=(struct Block *)malloc(sizeof(struct Block));
cout<<"请先输入主存大小(k)："<<endl;
cin>>temp->size;
temp->address=0;
temp->nowstate =0;
temp->next=freeHead;
temp->front=NULL;
freeHead->front=temp;
}

void Display(Block *p,Used *q)    //打印信息的函数
{
  cout<<"已分配分区信息(作业,始址,大小):"<<endl;
  while(q!=NULL)
  {
    cout<<q->usedArea->name<<','<<q->usedArea->address<<','<<q->usedArea->size<<endl;
    q=q->next;
  }
  cout<<"空闲链分区信息(始址,大小)："<<endl;
 while(p!=NULL)
 {
   cout<<p->address<<',';
   cout<<p->size<<endl;
   p=p->front;
 }
}

void Allocate(string reqName,int reqSize)   //分配函数
{    
  Block *p=freeHead->front ;
  Used *r1,*r2;
 while(p!=NULL)
 {
   if(reqSize<p->size)   //如果请求的分区的大小小于一个空闲分区的大小
   {
    Used *temp=new Used;
    temp->usedArea =p;
    Block *q=new Block;
    *q=*p;
    temp->usedArea ->name =reqName;  
    temp->usedArea ->size =reqSize;
    temp->usedArea ->front =q;
    temp->usedArea ->nowstate =1;
    q->size =q->size -reqSize;
    q->address =q->address + reqSize;   
    q ->next->front=q;
    if(q ->front!=NULL)
    q ->front->next=q;
    r1=usedHead;
    r2=usedHead->next;
    while(r2!=NULL&&r2->usedArea->address<temp->usedArea->address)
    {r1=r2;r2=r2->next;}
    r1->next=temp;
    temp->next=r2;
    break;
   }
   else if(reqSize==p->size)//如果请求的分区的大小等于一个空闲分区的大小
   {
    Used *temp=new Used;
    temp->usedArea =p;
    temp->usedArea ->name =reqName;
    temp->usedArea ->nowstate =1;
    p->next->front =p->front ;
    if(p->front!=NULL)
    p->front ->next =p->next ;
    r1=usedHead;
    r2=usedHead->next;
    while(r2!=NULL&&r2->usedArea->address<temp->usedArea->address)
    {r1=r2;r2=r2->next;}
    r1->next=temp;
    temp->next=r2;
    break;
   }
   p=p->front;
 }
  if(p==NULL)
    cout<<"资源不足请等待"<<endl;
}

void Recycle(string freeName)   //回收分区的函数
{
   Used *p=usedHead->next,*r=usedHead;
   Block *q;
   while(p!=NULL)
   {
      if(p->usedArea->name==freeName)//找到同名的作业后，再分四种情况讨论
	  {
         q=p->usedArea;
         int flag1=1,flag2=1;
         Block *p1=freeHead->front;
         Block *pfront,*pnext;
         while(p1->address<q->address)
		 {
            if(p1->address+p1->size==q->address)
			{flag1=0;pnext=p1;}
            p1=p1->front;
		 }
         if(q->address+q->size==p1->address)
		 {flag2=0;pfront=p1;}
         if(flag1==0)
		 {
            if(flag2==0)
			{
              pnext->front =pfront->front;
              pnext->size=pnext->size + q->size + pfront->size;
                if(pfront->front!=NULL)
                 pfront ->front ->next=pnext;
              r->next =p->next;
			}
            else 
			{pnext ->size +=q->size;
		     r->next =p->next ;
			}
		 }
         else
		 {
            if(flag2 ==0)
			{
             pfront ->address -=q->size;
             pfront ->size +=q->size ;
             r->next =p->next ;
			}
            else
			{
             Block *temp=freeHead;
             while(temp->address <=q->address )
				 temp=temp->front;
             q->front =temp;
             q->next =temp->next ;
             q->next->front =q;
             temp->next =q;
             q->nowstate =0;
             r->next =p->next ;
			}    
		 }
        break;
	  }
      r=p;
      p=p->next ;
   }
}

int main()     //主函数
{
  InitValue();//初始化
  int operate;//操作符1-申请资源 2-释放资源 3-打印信息 0-退出
  string name;
  int size;
  while(1)
  {
     cout<<"请选择操作功能"<<endl;
     cin>>operate;
     if(operate==1)
	 {   cout<<"请输入作业名(字符串)   空间大小(正整数)"<<endl;
         cin>>name>>size;
         Allocate(name,size);
	 }
     else if(operate==2)
	 {
        cout<<"请输入作业名(字符串)"<<endl;
        cin>>name;
        Recycle(name);
	 }
        else if(operate==3)  
			Display(freeHead->front,usedHead->next );
           else if(operate==0)
			   break;
  }
  return 0;
}