连续磁盘存储空间的分配和回收

struct FreeBlockMenu
{
	long FBbegin;//起始空闲块号
	long num;//空闲块个数
	struct FreeBlockMenu *next;
	struct FreeBlockMenu *front;
};
 
struct FiletoWrite
{
	char name[10];//装入的文件名，供回收磁盘空间时查找
	long size;//文件大小
	long addr_zhumian;//装入磁盘的首地址_柱面号
	long addr_cidao;//装入磁盘的首地址_磁道号
	long addr_jilu;//装入磁盘的首地址_物理记录号
	struct FiletoWrite *next;
	struct FiletoWrite *front;
};

//分配磁盘空间
int getMalloc()
{
	int flag = 0;
	struct FreeBlockMenu *p = FBhead;
	struct FiletoWrite *File;
	File = (struct FiletoWrite *)malloc(sizeof(struct FiletoWrite));
	printf("请输入装入的文件名：\n");
	scanf("%10s",File->name);
	printf("请输入所需要的磁盘空间大小：\n");
	scanf("%d",&File->size);
	for(p = FBhead->next;p != NULL;p = p->next)
	{
		flag = 1;
		if(p->num >= File->size )
		{
			//分配空间，块号转化为物理地址
			File->addr_zhumian = (p->FBbegin/6)/20;
			File->addr_cidao = (p->FBbegin/6)%20;
			File->addr_jilu = p->FBbegin%6;
			//加入文件链表中
			File->next = Filehead->next;
			if(Filehead->next != NULL)
			Filehead->next->front = File;
			Filehead->next = File;
			File->front = Filehead;
 
			if(p->num > File->size)
			{
				//修改该块的起始地址和块数
				p->FBbegin = p->FBbegin + File->size;
				p->num = p->num - File->size;
			}
			else if(p->num == File->size)
			{
				//从空闲块表中删除该结点
				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);
				}
			}
			printf("\n分配磁盘成功！\n该文件的物理地址为：(柱面号	磁道号	物理块号)\n");
			printf("			%d	%d	%d\n",File->addr_zhumian,File->addr_cidao,File->addr_jilu);
		}
	}
	if(flag == 0)
	{
		printf("对不起，目前没有足够的磁盘空间分配给该文件。");
		return 0;
	}
}
int showDisk();
 
//回收磁盘空间
int setFree()
{
	char name[10];
	int flag = 0;
	struct FiletoWrite *p = Filehead;
	printf("请输入要删除的文件名：\n");
	scanf("%10s",&name);
	for(p = Filehead;p != NULL;p = p->next)
	{
		if(strcmp(p->name , name)==0)//找到该文件
		{
			flag = 1;
			int houhebing=0,qianhebing=0;
			long m = p->addr_zhumian;
			long n = p->addr_cidao;
			long k = p->addr_jilu;
			long addr =120*m + 6*n + k;//块号
 
			//先考虑和后面的部分或许会有合并的情况
			long int tail=addr+p->size;
			struct FreeBlockMenu *pNode,*qNode;
 
			pNode=FBhead->next;
 
			while(pNode!=NULL)
			{
				if(pNode->FBbegin==tail)
				{
					pNode->FBbegin=addr;
					pNode->num=pNode->num+p->size;
					houhebing=1;
					qNode=pNode;
					break;
				}
				pNode=pNode->next;
			}
 
			//再考虑是否可以和前面的进行合并
			pNode=FBhead->next;
			while(pNode!=NULL)
			{
				if(pNode->FBbegin+pNode->num==addr)
				{
					if(houhebing==0)
					{
						pNode->num=pNode->num+p->size;
						qianhebing=1;
						break;
					}
					else if(houhebing==1)
					{
						pNode->num+=qNode->num;
						pNode=FBhead;
						while(pNode->next!=qNode)
							pNode=pNode->next;
						pNode->next=qNode->next;
						free(qNode);
						qianhebing=1;
						break;
					}
				}
				pNode=pNode->next;
			}
 
			//如果没有和前面的或者后面的进行合并，则新建一个表目
			if(qianhebing==0 && houhebing==0)
			{
		        	pNode=(struct FreeBlockMenu*)malloc(sizeof(struct FreeBlockMenu));
		         	pNode->FBbegin=addr;
		        	pNode->num=p->size;
				if(FBhead->next==NULL)
				{
					FBhead->next=pNode;
					pNode->front=FBhead;
					pNode->next=NULL;
					FBhead->front=NULL;
				}
				else
				{
					pNode->next=FBhead->next;
					FBhead->next->front=pNode;
					FBhead->next=pNode;
					pNode->front=FBhead;
				}
			}
 
			//在文件链表中删除该文件
			struct FiletoWrite *pPrev=p->front;
			if(p->next==NULL)
			{
				pPrev->next=NULL;
				free(p);
			}
			else
			{
				pPrev->next=p->next;
				p->next->front=pPrev;
			}
		}
	}
	if(flag == 0)
		printf("没有该文件！\n");
	else
		printf("删除文件成功！\n");
}
 
//显示磁盘空闲区表
int showDisk()
{
	struct FreeBlockMenu *p = FBhead;
	printf("\n磁盘空闲块表\n");
	printf("起始地址	空闲块大小\n");
	for(p = FBhead->next;p != NULL;p = p->next)
		printf("	%ld	%ld\n",p->FBbegin,p->num);
}
 
int main()
{
	char choose;	
	FBhead = (struct FreeBlockMenu *)malloc(sizeof(struct FreeBlockMenu));
	if(FBhead == NULL)
	{
		printf("error in allocating...\n");
	}
	else
		printf("successed\n");
	struct FreeBlockMenu *pNew=(struct FreeBlockMenu*)malloc(sizeof(struct FreeBlockMenu));
 
	pNew->FBbegin = 0;
	pNew->num = 24000;
	pNew->next = pNew->front = NULL;
 
	FBhead->next=pNew;
	FBhead->front=NULL;
	pNew->front=FBhead;
	pNew->next=NULL;
	Filehead = (struct FiletoWrite *)malloc(sizeof(struct FiletoWrite));
	Filehead->next = Filehead->front = NULL;
	char buf[128];
	do
	{
	system("clear");
	printf("---------------------------\n");
	printf("1.请求磁盘空间\n");
	printf("2.回收磁盘空间\n");
	printf("3.显示磁盘空闲区表\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':
				showDisk();
				gets(buf);break;
			case '4':
				exit(1);break;
			default:
				gets(buf);
				printf("输入错误！请重新输入。\n");
				break;
		}
		printf("\n");
		getchar();
	}while(choose != '4');
}