#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;
}
}
}