模拟可变分区管理（操作系统）

[c++]代码库
#include<stdio.h>
#include<iostream>
using namespace std;
 
 
 
 
struct  freelink{  //空闲链表
         int  len, address;  //   len为分区长度 
                             //   address为分区起始地址 
         struct  freelink  *next;
  };
 
struct  busylink{    //忙碌链表
         char name;         //  作业或进程名  name='S' 表示OS占用
         int  len , address;
         struct  busylink  *next;
  };
//全程量
  struct  freelink   *free_head=NULL;    //空闲链队列（带头结点）队首指针         
  struct  busylink   *busy_head=NULL;    //占用区队列队（带头结点）首指针                 
  struct  busylink   *busy_tail=NULL;    //占用区队列队尾指针
 
 
 
 
 
   void  start()     /* 设置系统初始状态*/
  {    
      struct freelink *p;
      struct busylink *q;
      free_head=(struct  freelink*)malloc(sizeof(struct freelink));
      free_head->next=NULL;  // 创建空闲链头结点
      busy_head=busy_tail=(struct busylink*)malloc(sizeof(struct  busylink));
      busy_head->next=NULL;  // 创建忙碌链头结点
      p=(struct freelink *)malloc(sizeof(struct freelink));
      p->address=64;
      p->len=640-64; 
      p->next=NULL; //分配操作系统占用的64K内存
      free_head->next =p;
      q=( struct  busylink *)malloc(sizeof(struct busylink));
      q->name='S';  /*  S表示操作系统占用  */
      q->len=64;  q->address=0;  q->next=NULL;
      busy_head->next=q;  busy_tail=q;
  }
 
 
 
 
      void requireMemo(char name,int require)     /*模拟内存分配*/
      {
          struct freelink *p,*u,*v;
          struct busylink *q;
          if(free_head->next->len<require)
          {
              cout<<"Can't allocate"<<endl;
              exit(1);
          }
          else
          {
              q=(struct busylink*)malloc(sizeof(struct busylink));
              q->name=name;
              q->address=free_head->next->address;
              q->len=require; 
              q->next=NULL;
              busy_tail->next=q;
              busy_tail=q;
 
          }
          p=free_head->next;
          free_head->next=p->next;
          if(p->len==require)
          {
              free(p);
          }
          else
          {
              p->address=p->address+require;
              p->len=p->len-require;
              u=free_head;
              v=free_head->next;
 
          }
 
          while((v!=NULL)&&v->len>p->len)
          {
              u=v;
              v=v->next;
          }
          u->next=p;
          p->next=v;
}
 
 
 
 
 
       void  freeMemo(char name)   // 模拟内存回收 
      {
         struct freelink *p,*u,*v;
         struct busylink *q,*w;
         q=busy_head;
         w=q->next;
         while((w!=NULL)&&(w->name!=name))
         {
             q=w;
             w=w->next;
         }
         if(w==NULL)
             printf("%c is not exit",name);
         else if(w==busy_tail)
         {
             busy_tail=q;
             q->next=w->next;
             q->len=w->len;
             q->address=w->address;
             free(w);
         }
         p=( struct freelink*) malloc(sizeof(struct freelink));
         p->len=p->len+q->len;
         p->address=p->address-q->address;
         u=free_head;
         v=free_head->next;
         if((v!=NULL)&&(v->len>p->len))
         {
             u=v;
             v=v->next;
         }
         else
         {
             u->next=p;
             p->next=v;
 
         }
      }
 
 
      void  printlink()  /* 输出内存空闲情况（自由链的结点） */
      {
          struct freelink *p;
          p=free_head->next;
          cout<<"分区长度        "<<"分区起始地址"<<endl;
         while(p!=NULL)
         {
             cout<<p->len<<"                "<<p->address<<endl;
             p=p->next;
         }
      }
 
 
 
 
 
void main()
{
    int n=1;
    start();
    char time;
    while(n)
    {
        cout<<"输入时刻：";
        cin>>time;
        switch(time)
        {
        case'1':
             requireMemo('A',8); 
             requireMemo('B',16); 
             requireMemo('C',64); 
             requireMemo('D',124);
              printlink();
              break;
        case'2':
             requireMemo('A',8); 
             requireMemo('B',16); 
             requireMemo('C',64); 
             requireMemo('D',124);
             freeMemo('C');
             printlink();
             break;
        case'3':
             requireMemo('A',8); 
             requireMemo('B',16); 
             requireMemo('C',64); 
             requireMemo('D',124);
             freeMemo('C');
             requireMemo('E',50);
             printlink();
             break;
        case'4':
             requireMemo('A',8); 
             requireMemo('B',16); 
             requireMemo('C',64); 
             requireMemo('D',124);
             freeMemo('C');
             requireMemo('E',50);
             freeMemo('D');
             printlink();
             break;
        default:
            cout<<"选择错误!"<<endl;
            break;
 
        }
    }
}
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