简单的文件系统实现

/*-----文件控制快信息-----*/

struct FCB

{

char name[9]; /*文件/目录名8位*/

char property; /*属性1位目录0位普通文件*/

int size; /*文件/目录字节数(原注释位盘块数)*/

int firstdisk; /*文件/目录起始盘块号*/

int next; /*子目录起始盘块号*/

int sign; /*1是根目录0不是根目录*/

}directitem[MSD+2];

};

/*------------------文件打开表项结构--------------------------*/ struct opentable /* size 104*/

{

struct openttableitem /* size 20*/

{

char name[9]; /*文件名*/

int firstdisk; /*起始盘块号*/

int size; /*文件的大小*/

}openitem[MOFN];

int cur_size; /*当前打文件的数目*/

};

/*-------------------------------------------------------------------*/ struct fatitem *fat; /*FAT表*/

struct direct *root; /*根目录*/

struct direct *cur_dir; /*当前目录*/

struct opentable u_opentable; /*文件打开表*/

int fd=-1; /*文件打开表的序号*/

char *bufferdir; /*记录当前路径的名称*/

char *fdisk; /*虚拟磁盘起始地址*/

void initfile();

void format();

void enter();

void halt();

int create(char *name);

int open(char *name);

int close(char *name);

int write(int fd,char *buf,int len);

int read(int fd,char *buf);

int del(char *name);

int mkdir(char *name);

int rmdir(char *name);

void dir();

int cd(char *name);

void print();

void show();

/*----------------------------------------------------------------------------------------------*/

/*------------------------------------------初始化文件系统--------------------------------------*/ void initfile()

{

fdisk = (char *)malloc(MEM_D_SIZE*sizeof(char)); /*申请1M空间*/

format();

free(fdisk);

}

/*----------------------------------------------------------------------------------------------*/

/*------------------------------------------格式化----------------------------------------------*/

void format()

{

int i;

FILE *fp;

fat = (struct fatitem *)(fdisk+DISKSIZE); /*计算FAT表地址(为什么向后偏移1k)*/ /*-----初始化FAT表------------*/

fat[0].item=-1; /*引导块*/

fat[0].em_disk='1';

for(i=1;i

{

fat[i].item=i+1;

fat[i].em_disk='1';

}

fat[ROOT_DISK_NO-1].item=-1;

fat[ROOT_DISK_NO-1].em_disk='1';

fat[ROOT_DISK_NO].item=-1; /*存放根目录的磁盘块号*/

fat[ROOT_DISK_NO].em_disk='1';

for(i=ROOT_DISK_NO+1;i

{

fat[i].item = -1;

fat[i].em_disk = '0';

}

/*-----------------------------------------------*/

root = (struct direct *)(fdisk+DISKSIZE+FATSIZE); /*根目录的地址*/ /*初始化目录*/

/*---------指向当前目录的目录项---------*/

root->directitem[0].sign = 1;

root->directitem[0].firstdisk = ROOT_DISK_NO;

strcpy(root->directitem[0].name,".");

root->directitem[0].next = root->directitem[0].firstdisk;

root->directitem[0].property = '1';

root->directitem[0].size = ROOT_DISK_SIZE;

/*-------指向上一级目录的目录项---------*/

root->directitem[1].sign = 1;

root->directitem[1].firstdisk = ROOT_DISK_NO;

strcpy(root->directitem[1].name,"..");

root->directitem[1].next = root->directitem[0].firstdisk;

root->directitem[1].property = '1';

root->directitem[1].size = ROOT_DISK_SIZE;

for(i=2;i

{

root->directitem[i].sign = 0;

root->directitem[i].firstdisk = -1;

strcpy(root->directitem[i].name,"");

root->directitem[i].next = -1;

root->directitem[i].property = '0';

root->directitem[i].size = 0;

}

/*-------测试写入文件的数据---------

for(i=0;i

{

printf("%d,%d/n",fat[i].item,fat[i].em_disk);

}

for(i=0;i

{

printf("%d,%s,%d,%c,%d,%d/n",root->directitem[i].firstdisk, root->directitem[i].name,root->directitem[i].next,

root->directitem[i].property,root->directitem[i].sign,

root->directitem[i].size);

}

for(i=0;i

{

fread(&fat[i],sizeof(struct fatitem),1,fp);

printf("%d,%d/n",fat[i].em_disk,fat[i].item);

}

for(i=0;i

{

fread(&root->directitem[i],sizeof(struct FCB),1,fp);

printf("%d,%s,%d,%c,%d,%d/n",root->directitem[i].firstdisk, root->directitem[i].name,root->directitem[i].next,

root->directitem[i].property,root->directitem[i].sign,

root->directitem[i].size);

}

------test end-----*/

if((fp = fopen("disk.dat","wb"))==NULL)

{

printf("Error:/n Cannot open file /n");

return;

}

if(fwrite(fdisk,MEM_D_SIZE,1,fp)!=1) /*把虚拟磁盘空间保存到磁盘文件中*/

{

printf("Error:/n File write error! /n");

}

fclose(fp);

}

/*----------------------------------------------------------------------------------------------*/

/*--------------------------------进入文件系统--------------------------------------------------*/

void enter()

{

FILE *fp;

int i;

fdisk = (char *)malloc(MEM_D_SIZE*sizeof(char)); /*申请1M空间*/

if((fp=fopen("disk.dat","rb"))==NULL)

{

printf("Error:/nCannot open file/n");

return;

}

if(!fread(fdisk,MEM_D_SIZE,1,fp)) /*把磁盘文件disk.dat 读入虚拟磁盘空间(内存)*/ {

printf("Error:/nCannot read file/n");

exit(0);

}

fat = (struct fatitem *)(fdisk+DISKSIZE); /*找到FAT表地址*/

root = (struct direct *)(fdisk+DISKSIZE+FATSIZE);/*找到根目录地址*/

fclose(fp);

/*--------------初始化用户打开表------------------*/

for(i=0;i

{

strcpy(u_opentable.openitem[i].name,"");

u_opentable.openitem[i].firstdisk = -1;

u_opentable.openitem[i].size = 0;

}

u_opentable.cur_size = 0;

cur_dir = root; /*当前目录为根目录*/

bufferdir = (char *)malloc(DIR_LENGTH*sizeof(char));

strcpy(bufferdir,"Root:"); /*显示根目录为E:*/

}

/*----------------------------------------------------------------------------------------------*/

/*------------------------------------退出文件系统----------------------------------------------*/

void halt()

{

FILE *fp;

int i;

if((fp=fopen("disk.dat","wb"))==NULL)

{

printf("Error:/nCannot open file/n");

return;

}

if(!fwrite(fdisk,MEM_D_SIZE,1,fp)) /*把虚拟磁盘空间(内存)内容读入磁盘文件disk.dat */

{

printf("Error:/nFile write error!/n");

}

fclose(fp);

free(fdisk);

free(bufferdir);

for(i=0;i

strcpy(u_opentable.openitem[i].name,"");

u_opentable.openitem[i].firstdisk = 0;

u_opentable.openitem[i].size = 0;

}

u_opentable.cur_size = 0; /*用户打开文件数清零*/

return;

}

/*----------------------------------------------------------------------------------------------*/

/*----------------------------------------创建文件----------------------------------------------*/ int create(char *name)

{

int i,j;

if(strlen(name)>8) /*文件名大于8位*/

return(-1);

for(i=2;i

{

if(cur_dir->directitem[i].firstdisk==-1)

break;

}

for(j=2;j

{

if(!strcmp(cur_dir->directitem[j].name,name))

break;

if(i>=MSD+2) /*无空目录项*/

return(-2);

if(u_opentable.cur_size>=MOFN) /*打开文件太多(第五层)*/

return(-3);

if(j

return(-4);

for(j=ROOT_DISK_NO+1;j

if(fat[j].em_disk=='0')

break;

}

if(j>=DISK_NUM)

return(-5);

fat[j].em_disk = '1'; /*将空闲块置为已经分配*/

/*-----------填写目录项-----------------*/

strcpy(cur_dir->directitem[i].name,name);

cur_dir->directitem[i].firstdisk = j;

cur_dir->directitem[i].size = 0;

cur_dir->directitem[i].next = j;

cur_dir->directitem[i].property = '0';

/*cur_dir->directitem[i].sign 丢失*/

/*---------------------------------*/

fd = open(name); /*打开所创建的文件*/

return 0;

}

/*----------------------------------------------------------------------------------------------*/

/*----------------------------------------打开文件----------------------------------------------*/ int open(char *name)

{

int i, j;

for(i=2;i

{

if(!strcmp(cur_dir->directitem[i].name,name))

break;

}

if(i>=MSD+2) /*文件不存在*/

return(-1);

/*--------是文件还是目录-----------------------*/

if(cur_dir->directitem[i].property=='1')/*是目录，不可打开读写*/ return(-4);

/*--------文件是否打开-----------------------*/

for(j=0;j

{

if(!strcmp(u_opentable.openitem[j].name,name)) break;

}

if(j

return(-2);

if(u_opentable.cur_size>=MOFN) /*文件打开太多*/

return(-3);

/*--------查找一个空闲用户打开表项-----------------------*/

for(j=0;j

{

if(u_opentable.openitem[j].firstdisk==-1)

break;

}

/*--------------填写表项的相关信息------------------------*/

u_opentable.openitem[j].firstdisk = cur_dir->directitem[i].firstdisk;

strcpy(u_opentable.openitem[j].name,name);

u_opentable.openitem[j].size = cur_dir->directitem[i].size;

u_opentable.cur_size++;

/*----------返回用户打开表表项的序号--------------------------*/

return(j);

}

/*----------------------------------------------------------------------------------------------*/

/*----------------------------------------关闭文件----------------------------------------------*/ int close(char *name)

{

int i;

for(i=0;i

{

if(!strcmp(u_opentable.openitem[i].name,name))

break;

}

if(i>=MOFN) /*--文件没有打开-*/

return(-1);

/*-----------清空该文件的用户打开表项的内容---------------------*/

strcpy(u_opentable.openitem[i].name,"");

u_opentable.openitem[i].firstdisk = -1;

u_opentable.openitem[i].size = 0;

u_opentable.cur_size--;

fd = -1; /*文件打开表的序号为-1 */

return 0;

}

/*----------------------------------------------------------------------------------------------*/

/*----------------------------------------写文件------------------------------------------------*/ int write(int fd, char *buf, int len)

{

char *first;

int item, i, j, k;

int ilen1, ilen2, modlen, temp;

/*----------用$ 字符作为空格# 字符作为换行符-----------------------*/

char Space = 32; /*SPACE的ASCII码值*/

char Endter= '/n';

for(i=0;i

{

if(buf[i] == '$') /*用$ 字符作为空格*/

buf[i] = Space;

else if(buf[i] == '#')

buf[i] = Endter;

}

/*----------读取用户打开表对应表项第一个盘块号-----------------------*/

item = u_opentable.openitem[fd].firstdisk;

/*-------------找到当前目录所对应表项的序号-------------------------*/

for(i=2;i

{

if(cur_dir->directitem[i].firstdisk==item)

break;

}

temp = i; /*-存放当前目录项的下标-*/

/*------找到的item 是该文件的最后一块磁盘块-------------------*/

while(fat[item].item!=-1)

{

item =fat[item].item; /*-查找该文件的下一盘块--*/

}

/*-----计算除该文件的最末地址-------*/

first = fdisk+item*DISKSIZE+u_opentable.openitem[fd].size%DISKSIZE;

/*-----如果最后磁盘块剩余的大小大于要写入的文件的大小-------*/

if(DISKSIZE-u_opentable.openitem[fd].size%DISKSIZE>len)

{

strcpy(first,buf);

u_opentable.openitem[fd].size = u_opentable.openitem[fd].size+len;

cur_dir->directitem[temp].size = cur_dir->directitem[temp].size+len;

}

else

{

for(i=0;i<(DISKSIZE-u_opentable.openitem[fd].size%DISKSIZE);i++)

{/*写一部分内容到最后一块磁盘块的剩余空间(字节)*/

first[i] = buf [i];

}

/*-----计算分配完最后一块磁盘的剩余空间(字节) 还剩下多少字节未存储-------*/

ilen1 = len-(DISKSIZE-u_opentable.openitem[fd].size%DISKSIZE);

ilen2 = ilen1/DISKSIZE;

modlen = ilen1%DISKSIZE;

if(modlen>0)

ilen2 = ilen2+1; /*--还需要多少块磁盘块-*/

/*调试时特别注意*/

for(j=0;j

{

for(i=ROOT_DISK_NO+1;i

{

if(fat[i].em_disk=='0')

break;

}

if(i>=DISK_NUM) /*--如果磁盘块已经分配完了-*/

return(-1);

first = fdisk+i*DISKSIZE; /*--找到的那块空闲磁盘块的起始地址-*/

if(j==ilen2-1) /*--如果是最后要分配的一块-*/

{

for(k=0;k

first[k] = buf[k];

}

else/*-如果不是要最后分配的一块--*/

{

for(k=0;k

first[k] =buf[k];

}

fat[item].item = i; /*--找到一块后将它的序号存放在上一块的指针中-*/

fat[i].em_disk = '1'; /*--置找到的磁盘快的空闲标志位为已分配-*/

fat[i].item = -1; /*--它的指针为-1 (即没有下一块)-*/

}

/*--修改文件打开表用户的长度-*/

u_opentable.openitem[fd].size = u_opentable.openitem[fd].size+len;

/*--修改目录项的文件长度-*/

cur_dir->directitem[temp].size = cur_dir->directitem[temp].size+len;

}

return 0;

}

/*----------------------------------------------------------------------------------------------*/

/*----------------------------------------读文件------------------------------------------------*/

int read(int fd, char *buf)

{

int len = u_opentable.openitem[fd].size;

char *first;

int i, j, item;

int ilen1, modlen;

item = u_opentable.openitem[fd].firstdisk;

if(len>u_opentable.openitem[fd].size) /*--欲读出的文件长度比实际文件长度长-*/ return(-1);

ilen1 = len/DISKSIZE;

modlen = len%DISKSIZE;

if(modlen!=0)

ilen1 = ilen1+1; /*--计算文件所占磁盘的块数-*/

first = fdisk+item*DISKSIZE; /*--计算文件的起始位置-*/

for(i=0;i

{

if(i==ilen1-1) /*--如果在最后一个磁盘块-*/

{

for(j=0;j

buf[i*DISKSIZE+j] = first[j];

}

else /*--不在最后一块磁盘块-*/

{

for(j=0;j

buf[i*DISKSIZE+j] = first[j];

item = fat[item].item; /*-查找下一盘块-*/

first = fdisk+item*DISKSIZE;

}

}

return 0;

}

/*----------------------------------------------------------------------------------------------*/

/*----------------------------------------删除文件----------------------------------------------*/ int del(char *name)

{

int i,cur_item,item,temp;

for(i=2;i

{

if(!strcmp(cur_dir->directitem[i].name,name))

break;

}

cur_item = i; /*--用来保存目录项的序号,供释放目录中-*/

if(i>=MSD+2) /*--如果不在当前目录中-*/

return(-1);

if(cur_dir->directitem[cur_item].property!='0') /*--如果删除的(不)是目录-*/ return(-3);

for(i=0;i

{

if(!strcmp(u_opentable.openitem[i].name,name))

return(-2);

}

item = cur_dir->directitem[cur_item].firstdisk;/*--该文件的起始盘块号-*/

while(item!=-1) /*--释放空间,将FAT表对应项进行修改-*/

{

temp = fat[item].item;

fat[item].item = -1;

fat[item].em_disk = '0';

item = temp;

}

/*-----------------释放目录项-----------------------*/

cur_dir->directitem[cur_item].sign = 0;

cur_dir->directitem[cur_item].firstdisk = -1;

strcpy(u_opentable.openitem[cur_item].name,"");

cur_dir->directitem[cur_item].next = -1;

cur_dir->directitem[cur_item].property = '0';

cur_dir->directitem[cur_item].size = 0;

return 0;

}

/*----------------------------------------------------------------------------------------------*/

/*---------------------------------------创建子目录---------------------------------------------*/ int mkdir(char *name)

{

int i,j;

struct direct *cur_mkdir;

if(strchr(name,'//'))/*如果目录名中有'/'字符*/

return(-4);

if(!strcmp(name,"."))

return(-6);

if(!strcmp(name,".."))

return(-6);

if(strlen(name)>8) /*-如果目录名长度大于8位-*/

return(-1);

for(i=2;i

{

if(cur_dir->directitem[i].firstdisk==-1)

break;

}

if(i>=MSD+2) /*-目录/文件已满-*/

return(-2);

for(j=2;j

{

if(!strcmp(cur_dir->directitem[j].name,name))

break;

}

if(j

return(-3);

for(j=ROOT_DISK_NO+1;j

{

if(fat[j].em_disk=='0')

break;

}

if(j>=DISK_NUM)

return(-5);

fat[j].em_disk='1'; /*-将该空闲块设置为已分配-*/

/*-------------填写目录项----------*/

strcpy(cur_dir->directitem[i].name,name);

cur_dir->directitem[i].firstdisk=j;

cur_dir->directitem[i].size=ROOT_DISK_SIZE;

cur_dir->directitem[i].next=j; /*-指向子目录(其实就是其本身)的起始盘块号-*/ cur_dir->directitem[i].property='1';

/*-sign=1为根标志,这里可以省略-*/

/*-所创目录在虚拟磁盘上的地址(内存物理地址)-*/

cur_mkdir=(struct direct *)(fdisk+cur_dir->directitem[i].firstdisk*DISKSIZE);

/*-初始化目录-*/

/*-指向当前目录的目录项-*/

cur_mkdir->directitem[0].sign=0;

cur_mkdir->directitem[0].firstdisk=cur_dir->directitem[i].firstdisk;

strcpy(cur_mkdir->directitem[0].name,".");

cur_mkdir->directitem[0].next=cur_mkdir->directitem[0].firstdisk;

cur_mkdir->directitem[0].property='1';

cur_mkdir->directitem[0].size=ROOT_DISK_SIZE;

/*-指向上一级目录的目录项-*/

cur_mkdir->directitem[1].sign=cur_dir->directitem[0].sign;/*-指向上一级目录的目录项-*/ cur_mkdir->directitem[1].firstdisk=cur_dir->directitem[0].firstdisk;

strcpy(cur_mkdir->directitem[1].name,"..");

cur_mkdir->directitem[1].next=cur_mkdir->directitem[1].firstdisk;

cur_mkdir->directitem[1].property='1';

cur_mkdir->directitem[1].size=ROOT_DISK_SIZE;

for(i=2;i

{

cur_mkdir->directitem[i].sign=0;

cur_mkdir->directitem[i].firstdisk=-1;

strcpy(cur_mkdir->directitem[i].name,"");

cur_mkdir->directitem[i].next=-1;

cur_mkdir->directitem[i].property='0';

cur_mkdir->directitem[i].size=0;

}

return 0;

}

/*----------------------------------------------------------------------------------------------*/

/*---------------------------------------删除子目录---------------------------------------------*/

int rmdir(char *name)

{

int i,j,item;

struct direct *temp_dir;

/*-检查当前目录项中有无该目录-*/

for(i=2;i

{

if(!strcmp(cur_dir->directitem[i].name,name))

break;

}

if(cur_dir->directitem[i].property!='1')/*-删除的不是目录-*/

return(-3);

if(i>=MSD+2) /*-没有这个文件或目录-*/

return(-1);

/*-判断要删除的目录有无子目录-*/

/*-要删除的目录起始地址-*/

temp_dir=(struct direct *)(fdisk+cur_dir->directitem[i].next*DISKSIZE); for(j=2;j

{

if(temp_dir->directitem[j].next!=-1)

break;

}

if(j

return(-2); /*-有关联则报错,也可以采取级联删除,像Windows-*/

/*------------找到起始盘块号,并将其释放----------------*/

item=cur_dir->directitem[i].firstdisk;

fat[item].em_disk='0';

/*-修改目录项-*/

cur_dir->directitem[i].sign=0;

cur_dir->directitem[i].firstdisk=-1;

strcpy(cur_dir->directitem[i].name,"");

cur_dir->directitem[i].next=-1;

cur_dir->directitem[i].property='0';

cur_dir->directitem[i].size=0;

return 0;

}