分页管理方式下采用位示图表示实现主存分配和回收

struct bitGraph
{
	int a[8][8];//位示图
	int freebit;//空闲块数
}BG;
 
//进程的数据结构
struct proc
{
	char name[10];//进程名
	int *PT;//页表
	int size;//进程所需要的空间
	struct proc *next;
	struct proc *front;
};

//分配内存
int getMalloc()
{
	int i = 0,j = 0,p = 0,k = 0,flag = 0;
	struct proc *process;
	process = (struct proc *)malloc(sizeof(struct proc));
	printf("请输入进程名：\n");
	scanf("%10s",process->name);
	process->next = head->next;
	if(head->next != NULL)
		head->next->front = process;
	head->next = process;
	process->front = head;
	printf("请输入进程所需内存大小：\n");
	scanf("%d",&process->size);
	if(process->size > BG.freebit)
	{
		printf("对不起，空闲空间不足以分配如此多内存给该进程。\n");
		return 0;
	}
	else
	{
		process->PT = new int [process->size];
		for(i=0;i<8 && flag==0;i++)
			for(j=0;j<8 && flag==0;j++)
			{
				if(!BG.a[i][j])
				{
					BG.a[i][j] = 1;
					BG.freebit--;
					process->PT[k] = 8*i + j;
					k++;
					if(k == process->size)
						flag = 1;
				}
			}
	}
	printf("\n位示图：\n");
	for(i=0;i<8;i++)
	{
		for(j=0;j<8;j++)
			printf("%d",BG.a[i][j]);
		printf("\n");
	}
}
 
//回收内存
int setFree()
{
	char name[10];
	int flag = 0,i = 0,j = 0;
	struct proc *p = head;
	printf("请输入需要回收的进程名：");
	scanf("%10s",&name);
	for(p = head;p != NULL;p = p->next)
	{
		if(strcmp(p->name , name)==0)//找到该进程，将其从进程链表中删除，并改写位示图
		{
			flag = 1;
			for(i=0;i < p->size;i++)
			{
				int m = p->PT[i]/8;
				int n = p->PT[i]%8;
				BG.a[m][n]= 0;
				BG.freebit++;
			}
			if(p->front != NULL)
			{
				if(p->next != NULL)
				{
					p->front->next = p->next;
					p->next->front = p->front;
					free(p);
				}
				else
				{
					p->front->next = p->next;
					free(p);
				}
			}
			else
			{
				p->next->front = p->front;
				free(p);
			}
		}
	}
	if(flag == 0)
		printf("没有该进程！\n");
	else
		printf("回收成功！\n");
	printf("\n位示图：\n");
	for(i=0;i<8;i++)
	{
		for(j=0;j<8;j++)
			printf("%d",BG.a[i][j]);
		printf("\n");
	}
}
 
//显示进程页表
int showMemo()
{
	char name[10];
	int flag = 0,i = 0;
	struct proc *p = head;
 
	printf("请输入进程名：");
	scanf("%10s",&name);
	for(p = head;p != NULL;p = p->next)
	{
		if(strcmp(p->name , name)==0)
		{
			printf("	进程名  页号    块号\n");
			for(i=0;i<p->size;i++)
			{
				printf("%10s	%d	%d\n",p->name,i,p->PT[i]);
				flag = 1;
			}
		}
	}
	if(flag == 0)
		printf("没有该进程！\n");
}
 
int main()
{
	char choose;
	BG.a[8][8] = 0;
	BG.freebit = 64;
 
	head = (struct proc *)malloc(sizeof(struct proc));
	if(head==NULL)
	{
		printf("error in allocating...\n");
	}
	else
		printf("successed\n");
	head->next = head->front = NULL;//建立进程的头结点
        char buf[128];
	do
	{
	system("clear");
	printf("---------------------------\n");
	printf("1.新进程请求内存空间\n");
	printf("2.回收空间\n");
	printf("3.显示进程页表\n");
	printf("4.退出\n");
	printf("---------------------------\n");
		printf("请选择：");
		scanf("%c",&choose);
		switch(choose)
		{
			case '1':
				getMalloc();
				gets(buf);break;
			case '2':
				setFree();
				gets(buf);break;
			case '3':
				showMemo();
				gets(buf);break;
			case '4':
				exit(1);gets(buf);break;
			default:
				gets(buf);
				printf("输入错误！请重新输入。\n");break;
		}
		printf("\n");
		getchar();
	}while(choose != '4');
}