实验二 分区式存储管理
实验性质：设计
建议学时：2学时
实验目的：
通过这次实验，加深对内存管理的认识，进一步掌握内存的分配、回收算法的思想。
实验内容：
设计程序模拟内存的动态分区法存储管理。内存空闲区使用自由链管理，釆用最坏适应算法从自 由链中寻找空闲区进行分配，内存回收时假定不做与相邻空闲区的合并。
假定系统的内存共640K,初始状态为操作系统本身占用64K。在tl时间之后，有作业A、B、C、
D分别请求8K、16K、64K、124K的内存空间；在t2时间之后，作业C完成；在t3时间之后，作业
E请求50K的内存空间；在t4时间之后，作业D完成。要求编程序分别输出tl、t2、t3、t4时刻内存
的空闲区的状态。
实现提示（C语言）:
1.程序中自由链队列的结点类型可描述如下：
struct freelink（
int len, address; //len 为分区长度
//address为分区起始地址
struct freelink *next;
}
内存占用区用链表描述，其结点类型描述如下：
struct busylink{
char name; //作业或进程名 name='S'表示OS占用
int len , address;
struct busylink *next;
}
并设全程量：
struct freelink *free_head=NULL; //自由链队列（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
* busy_tail=NULL ； //占用区队列队尾指针
2.设计子函数：
void start（void）; /*设置系统初始状态*/
struct freelink * p;
struct busylink *q;
free_head=(struct freelink*)malloc(sizeo instruct freelink));
free_head->next=NULL; //创建自由链头结点
busy_head=busy_tail=(struct busylinktf!)malloc(sizeof(struct busy link)); busy_head->next=NULL; //创建占用链头结点 p=( struct freelink *)malloc(sizeof(struct freelink)); p->add ress=64;
p->Ien=640-64; //OS 占用了 64K
p->next=NULL;
freehea d->n ext=p;
q=( struct busy link *)malloc(sizeofi(struct busylink)); q->name=,S,; //S表示操作系统占用
q->len=64; q->address=O; q->n ext=NULL;
b usyh ea d->next=q; busy_tail=q;
void }
requireMemo(char name, int require); //模拟内存分配
void freeMemo(cha r name); //模拟内存回收
void past(int time); //模拟系统过了 time时间
void printlinkQ; //输出内存空闲情况（自由链的结点）
3.设计主函数：
int main()
{
start();
past(1);
requireMemo('A', 8);
requireMemo('B', 16);
requireMemo('C', 400);
requireMemo('D', 124);
printlink();
past(2);
freeMemo('C');
printlink();
past(3);
requireMemo('E', 200);
printlink();
freeMemo('B');
printlink();
freeMemo('D');
printlink();
system("pause");
return 0;
}
实验要求：
1 上机前仔细编好程序；
2 上机时独立调试程序；
3 提交实验报告，包括纸质稿和电子稿两部分。实验报告要求详见实验报告模板。
实验用例：
代码展示
#include <iostream>
#include <fstream>
using namespace std;
struct freelink
{
int len, address;
freelink *next;
};
struct busylink
{
char name;
int len, address;
busylink *next;
};
freelink *free_head = NULL;
busylink *busy_head = NULL;
busylink *busy_tail = NULL;
// 函数声明
void start();
// 模拟内存分配
void requireMemo(char name, int require);
// 更新空闲区前先删除同首地址节点
void delete_freearea(int address);
// 内存回收时删除占用区节点
void delete_busyarea(int address);
// 将节点按序插入空闲区
void insert_freearea(freelink *my);
// 模拟内存回收
void freeMemo(char name);
// 模拟系统时间
void past(int time);
// 输出内存空闲情况
void printlink();
int main()
{
start();
past(1);
requireMemo('A', 8);
requireMemo('B', 16);
requireMemo('C', 400);
requireMemo('D', 124);
printlink();
past(2);
freeMemo('C');
printlink();
past(3);
requireMemo('E', 200);
printlink();
freeMemo('B');
printlink();
freeMemo('D');
printlink();
system("pause");
return 0;
}
void start()
{
freelink *p;
busylink *q;
free_head = new freelink;
free_head->next = NULL;
busy_head = busy_tail = new busylink;
busy_head->next = NULL;
p = new freelink;
p->address = 64;
p->len = 640 - 64;
p->next = NULL;
free_head->next = p;
q = new busylink;
q->name = 'S';
q->len = 64;
q->address = 0;
q->next = NULL;
busy_head->next = q;
busy_tail = q;
}
void requireMemo(char name, int require)
{
freelink *p = free_head->next;
if (p->len >= require)
{
busylink *tmp = new busylink;
tmp->name = name;
tmp->len = require;
tmp->address = p->address;
tmp->next = NULL;
// 放入占用区末尾
busy_tail->next = tmp;
busy_tail = tmp;
// 更新空闲区
freelink *q = new freelink;
q->next = NULL;
q->len = p->len - require;
q->address = p->address;
delete_freearea(q->address);
q->address = p->address + require;
insert_freearea(q);
}
else
{
printf("Insufficient free space\n");
}
}
void delete_freearea(int address)
{
freelink *p = free_head;
while (p->next)
{
if (address == p->next->address)
{
p->next = p->next->next;
return;
}
p = p->next;
}
}
void delete_busyarea(int address)
{
busylink *p = busy_head;
while (p->next)
{
if (address == p->next->address)
{
p->next = p->next->next;
if (p->next == NULL)
{
busy_tail = p;
}
return;
}
p = p->next;
}
}
void insert_freearea(freelink *my)
{
freelink *q = free_head->next;
int mystart = my->address;
int myend = my->address + my->len;
freelink *beforenode = NULL;
freelink *afternode = NULL;
while (q)
{
if (q->address + q->len == mystart)
{
beforenode = q;
}
if (myend == q->address)
{
afternode = q;
}
q = q->next;
}
if (beforenode)
{
delete_freearea(beforenode->address);
my->address = beforenode->address;
my->len += beforenode->len;
}
if (afternode)
{
delete_freearea(afternode->address);
my->len += afternode->len;
}
freelink *p = free_head;
while (p->next)
{
if (my->len >= p->next->len)
{
my->next = p->next;
p->next = my;
return;
}
p = p->next;
}
my->next = p->next;
p->next = my;
}
void freeMemo(char name)
{
busylink *busyp = busy_head->next;
freelink *freep = free_head->next;
while (busyp)
{
if (busyp->name == name)
{
freelink *tmp = new freelink;
tmp->address = busyp->address;
tmp->len = busyp->len;
tmp->next = NULL;
delete_busyarea(tmp->address);
insert_freearea(tmp);
}
busyp = busyp->next;
}
}
void past(int time)
{
printf("After t%d:\n", time);
}
void printlink()
{
printf("The memory usage is:\n");
printf("Job\tStart address\tSize\n");
busylink *p = busy_head->next;
while (p)
{
printf("%c\t%d\t\t%d\n", p->name, p->address, p->len);
p = p->next;
}
printf("Memory free area is\n");
printf("Start address\tSize\n");
freelink *q = free_head->next;
while (q)
{
printf("%d\t\t%d\n", q->address, q->len);
q = q->next;
}
printf("------------------------------------\n");
}