操作系統實驗報告——文件算法

操作系統實驗報告——文件算法

**1.實驗名稱：*文件操作算法的實現
2.實驗要求：
（1）理解文件操作的基本思想.
（2）掌握文件的基本操作算法（創建、刪除、打開、關閉、讀、寫）
（3）用C或C++語言編程實現文件基本操作算法。
3.實驗方式： 通過上機，實際調試運行程序。
4.實驗環境：
（1）硬件環境：PC機一臺；
（2）軟件環境：Windows 10操作系統， Ｃ或Ｃ＋＋程序設計語言。
5.實驗過程：
（1）算法描述：
文件的創建與打開。
FILE apply_room(char sys_name){
f = fopen(sys_name,“w+b”); //創建一個新的可讀寫的二進制文件
fseek(f,SYS_SIZE,SEEK_SET);
fputc(EOF, f);
fclose(f);
return fopen(sys_name,“r+b”);//打開一個可讀寫的二進制文件
}
void create():{
int i,inode_num;
long t;
char name[12];
printf(“輸入文件名:”);
scanf("%s",name);
getchar();
if(namei(name)!=-1)
printf(“文件已退出!\n”);
else{
inode_num=ialloc();
strcpy(file.name,name);
file.inode_num=inode_num;
fseek(f,BLOCK_SIZE+inode_num16,SEEK_SET);
fwrite(&file,sizeof(struct filelist),1,f);
inode.i_size=0;
inode.block_amount=0;
for(i=0;i<16;i++) inode.i_addr[i]=0;
time(&t);
strcpy(inode.create_time,ctime(&t));
fseek(f,4BLOCK_SIZE+inode_numsizeof(struct inode),SEEK_SET);
fwrite(&inode,sizeof(struct inode),1,f);
p->s_inode[inode_num]=0;
printf(“創建成功!\n”);
}
}
在文件系統中創建自己的文件
void open_file(){
int i=0,j=0,k=0;
int m,n;
char name[12];
printf(“輸入文件名:”);
scanf("%s",name);
getchar();
n=namei(name);
if(n==-1)
printf(“文件不存在!\n”);
else if(p->s_inode[n]>0)
printf(“文件已打開\n”);
else{
while(fcb[i].used1) i++;
while(table[j].f_node) j++;
while(fd[k].t_node) k++;
fd[k].t_node=&table[j];
table[j].f_node=&fcb[i];
strcpy(fcb[i].name,name);
fcb[i].inode_num=n;
fcb[i].used=1;
fseek(f,4BLOCK_SIZE+nsizeof(struct inode),SEEK_SET);
fread(&inode,sizeof(struct inode),1,f);
fcb[i].i_size=inode.i_size;
fcb[i].block_amount=inode.block_amount;
for(m=0;m<16;m++) fcb[i].i_addr[m]=inode.i_addr[m];
p->s_inode[n]=k+100;
printf(“文件已打開!\n”);
}
}
打開剛剛或之前建立的文件
文件的讀寫
void write_file() {
int k,block_amount,n,size=0,i=0;
long block_num;
char ch,name[12];
printf(“輸入文件名”);
scanf("%s",name);
getchar();
n=name_i(name);
if(n-1) printf(“文件不存在或未打開!\n”);
else{
k=p->s_inode[n]-100;
ptr=fd[k].t_node->f_node;
while(iblock_amount){
block_num=ptr->i_addr[i];
myfree(block_num);
i++;
}
block_amount=0;
printf(“輸入文件的上下文：（用“”結束）\n");
while((ch=getchar())!=’’&&block_amount<16){
size++;
if(size1){
block_num=myalloc();
inode.i_addr[block_amount]=ptr->i_addr[block_amount]=block_num;
block_amount++;
fseek(f,(block_num-1)BLOCK_SIZE,SEEK_SET);
}
fputc(ch,f);
}
getchar();
inode.i_size=ptr->i_size=size;
inode.block_amount=ptr->block_amount=block_amount;
fseek(f,4BLOCK_SIZE+n*sizeof(struct inode),SEEK_SET);
fwrite(&inode,sizeof(struct inode),1,f);
}
}
void read_file() {
int k,n,block_amount,size;
int i=0;
long block_num;
char name[12],buf[512];
printf(“輸入文件名:”);
scanf("%s",name);
getchar();
n=name_i(name);
if(n-1)
printf(“文件不存在或未打開!”);
else{
k=p->s_inode[n]-100;
ptr=fd[k].t_node->f_node;
size=ptr->i_size;
block_amount=ptr->block_amount;
for(i=0;i<block_amount;i++){
block_num=ptr->i_addr[i];
fseek(f,(block_num-1)*BLOCK_SIZE,SEEK_SET);
if(size>512) {fread(buf,sizeof(char),512,f); size=size-512;}
else{
fread(buf,sizeof(char),size,f);
buf[size]=’\0’;
}
printf(”%s",buf);
}
}
printf("\n");
}
退出文件系統
void myexit(){
int i=0;
char ch;
while(fcb[i].used0) i++;
if(i<5){
getchar();
printf(“一些文件仍處於打開狀態!!!\n”);
printf(“輸入“q”或其他鍵返回\n”);
scanf("%c",&ch);
if(ch’q’){
while(i<5){
if(fcb[i].used==1) p->s_inode[fcb[i].inode_num]=0;
i++;
}
fseek(f,0,SEEK_SET);
fwrite(p,sizeof(struct filsys),1,f);
exit(0);
}
getchar();
}
else{
fseek(f,0,SEEK_SET);
fwrite(p,sizeof(struct filsys),1,f);
exit(0);
}
} //退出此文件系統

（2）實現代碼：

#include <stdio.h>  
#include <stdlib.h>  
#include <ctype.h>  
#include <string.h>  
#include <time.h>  
#define SYS_SIZE 0XFFFFF*100          
#define BLOCK_SIZE 512                
FILE *f;  
struct filsys{                        
    	int s_nfree;                      
    	long s_free[100];                 
    	int s_ninode;                     
    	int s_inode[96];                                                     
}*p;  
struct index_block{                   
    	int s_nfree;  
    	long s_free[96];  
}q;  
struct filelist{                      
    	char name[14];                    
    	int inode_num;                    
}file;  
struct inode{                         
    	int i_size;                       
    	int block_amount;                 
    	long i_addr[16];                  
    	char create_time[25];             
}inode;  
struct fcb{                           
    	char name[12];                    
    	int inode_num;                    
    	int used;                         
    	int i_size;                       
    	int block_amount;                 
    	long i_addr[16];                  
}fcb[5],*ptr;  
struct open_file_table{               
    	int offset;                       
    	struct fcb* f_node;               
}table[5];  
struct fd{                            
    	struct open_file_table* t_node;   
}fd[5];  
 
FILE* apply_room(char *sys_name){    
f = fopen(sys_name,"w+b");    //創建一個新的可讀寫的二進制文件  
 	fseek(f,SYS_SIZE,SEEK_SET);       
    	fputc(EOF, f);          //打開一個可讀寫的二進制文件  
}  
void myfree(long block_num){    
int i;  
if(p->s_nfree<100){               
p->s_free[p->s_nfree]=block_num;  
p->s_nfree++;  
}  
else{                            
q.s_nfree=p->s_nfree;          
       		for(i=0;i<100;i++)  
          		q.s_free[i]=p->s_free[i];  
       		fseek(f,(block_num-1)*BLOCK_SIZE,SEEK_SET);  
       		fwrite(&q,sizeof(struct index_block),1,f);   
       		p->s_nfree=1;                  
       		p->s_free[0]=block_num;  
}  
}   
long myalloc(){                       
    	int i;  
    	long a;  
    	p->s_nfree--;  
    	if(p->s_nfree==0){                
       		a=p->s_free[0];  
       		fseek(f,(a-1)*BLOCK_SIZE,SEEK_SET);  
       		fread(&q,sizeof(struct index_block),1,f);  
       		p->s_nfree=q.s_nfree;          
       		for(i=0;i<100;i++)  
         		p->s_free[i]=q.s_free[i];  
       		return a;  
    		}
else
return p->s_free[p->s_nfree];  
}  
void init(){    
int j;  
    	long i;  
    	p->s_nfree=1;  
    	p->s_free[0]=0;  
    	p->s_ninode=96;  
    	for(i=0;i<96;i++)  
       		p->s_inode[i]=-1;              
    	for(i=22;i<=SYS_SIZE/BLOCK_SIZE;i++)  
       		myfree(i);                     
    	j=p->s_nfree+1;  
    	while(j<100)  
       		p->s_free[j++]=0;              
    	fseek(f,0,SEEK_SET);  
    	fwrite(p,sizeof(struct filsys),1,f);  
}   
int ialloc(){                         
    	int i=0;  
    	while(p->s_inode[i]>=0) 
i++;      
    	p->s_inode[i]=0;                  
    	p->s_ninode--;  
    	return i;  
}  
int namei(char *name){    
int k=0;  
   	while(k<96){  
   		if(p->s_inode[k]!=-1){       
          		fseek(f,BLOCK_SIZE+k*16,SEEK_SET);  
          		fread(&file,sizeof(struct filelist),1,f);  
          		if(!strcmp(file.name,name))  
             			return file.inode_num;  
}  
         k++;  
    	};  
return -1;                     
}   
int name_i(char *name){    
int k=0;  
    	do{  
       		if(fcb[k].used==1){        
          		if(!strcmp(fcb[k].name,name))   
            			return fcb[k].inode_num;  
       		}  
       		k++;  
    	}
while(k<5);  
    	return -1;                     
}  
void create(){    
 	int i,inode_num;  
    	long t;  
    	char name[12];  
    	printf("輸入文件名:");  
    	scanf("%s",name);  
   	getchar();  
    	if(namei(name)!=-1) printf("文件已退出!\n");  
    	else{                             
       		inode_num=ialloc();        
       		strcpy(file.name,name);  
       		file.inode_num=inode_num;  
       		fseek(f,BLOCK_SIZE+inode_num*16,SEEK_SET);  
      		fwrite(&file,sizeof(struct filelist),1,f);  
      		inode.i_size=0;                       
    		inode.block_amount=0;  
     		for(i=0;i<16;i++) 
inode.i_addr[i]=0;  
    		time(&t);  
   		strcpy(inode.create_time,ctime(&t));  
  		fseek(f,4*BLOCK_SIZE+inode_num*sizeof(struct inode),SEEK_SET);  
    		fwrite(&inode,sizeof(struct inode),1,f);  
    		p->s_inode[inode_num]=0;      
    		printf("創建成功!\n");  
    	}  
}   
void open_file(){
int i=0,j=0,k=0;  
    	int m,n;  
    	char name[12];  
    	printf("輸入文件名:");  
    	scanf("%s",name);  
    	getchar();  
   	n=namei(name);               
   	if(n==-1) 	
printf("文件不存在!\n");  
   	else if(p->s_inode[n]>0) 
printf("文件已打開\n");  
   	else{  
       		while(fcb[i].used==1) 
i++;      
       		while(table[j].f_node) 
j++;     
       		while(fd[k].t_node) 
k++;        
       		fd[k].t_node=&table[j];         
       		table[j].f_node=&fcb[i];        
       		strcpy(fcb[i].name,name);  
       		fcb[i].inode_num=n;  
       		fcb[i].used=1;  
      		fseek(f,4*BLOCK_SIZE+n*sizeof(struct inode),SEEK_SET);  
       		fread(&inode,sizeof(struct inode),1,f);  
       		fcb[i].i_size=inode.i_size;  
       		fcb[i].block_amount=inode.block_amount;  
       		for(m=0;m<16;m++) 
fcb[i].i_addr[m]=inode.i_addr[m];  
       		p->s_inode[n]=k+100;            
       		printf("文件已打開!\n");  
    	}  
}  
void write_file(){    
int k,block_amount,n,size=0,i=0;  
    	long block_num;  
    	char ch,name[12];  
    	printf("輸入文件名");  
    	scanf("%s",name);  
    	getchar();  
    	n=name_i(name);            
    	if(n==-1) 
printf("文件不存在或未打開!\n");  
    	else{  
      		k=p->s_inode[n]-100;    
      		ptr=fd[k].t_node->f_node;  
      		while(i<ptr->block_amount){  
         		block_num=ptr->i_addr[i];  
         		myfree(block_num);  
         		i++;  
       		}	  
       		block_amount=0;  
       		printf("輸入文件的上下文：（用“*”結束）\n");  
       		while((ch=getchar())!='*'&&block_amount<16){  
          		size++;  
          		if(size==1){            
             			block_num=myalloc();     
             			inode.i_addr[block_amount]=ptr->i_addr[block_amount]=block_num;  
             			block_amount++;  
             			fseek(f,(block_num-1)*BLOCK_SIZE,SEEK_SET);  
          		}  
          		fputc(ch,f);  
       		}  
       		getchar();  
       		inode.i_size=ptr->i_size=size;  
       		inode.block_amount=ptr->block_amount=block_amount;  
       		fseek(f,4*BLOCK_SIZE+n*sizeof(struct inode),SEEK_SET);  
       		fwrite(&inode,sizeof(struct inode),1,f);     
}  
}
void read_file(){    
 	int k,n,block_amount,size;  
 	int i=0;  
    	long block_num;  
    	char name[12],buf[512];  
    	printf("輸入文件名:");  
    	scanf("%s",name);  
    	getchar();  
    	n=name_i(name);          
    	if(n==-1) printf("文件不存在或未打開!");  
    	else{  
       		k=p->s_inode[n]-100;  
       		ptr=fd[k].t_node->f_node;  
       		size=ptr->i_size;  
       		block_amount=ptr->block_amount;  
       		for(i=0;i<block_amount;i++){  
          		block_num=ptr->i_addr[i];                      
          		fseek(f,(block_num-1)*BLOCK_SIZE,SEEK_SET);    
          		if(size>512){
fread(buf,sizeof(char),512,f);   
size=size-512;
}  
          		else{  
             			fread(buf,sizeof(char),size,f);     
             			buf[size]='\0';  
          		}  
          		printf("%s",buf);  
       		}  
    	}  
    	printf("\n");  
}  
void del_file(){   
int n,i=0;  
    	long block_num;  
    	char name[12];  
   	printf("輸入文件名:");  
    	scanf("%s",name);  
    	getchar();  
    	n=namei(name);            
    	if(n==-1) 
printf("文件不存在!\n");       
    	else if(p->s_inode[n]>0) 
printf("文件已打開！請先關閉!\n");  
    	else{  
       		p->s_inode[n]=-1;      
       		fseek(f,4*BLOCK_SIZE+n*sizeof(struct inode),SEEK_SET);  
       		fread(&inode,sizeof(struct inode),1,f);    
       		while(i<inode.block_amount){  
          		block_num=inode.i_addr[i];  
          		myfree(block_num);       
          		i++;  
       		}  
       	strcpy(file.name,"");       
       	file.inode_num=0;  
       	fseek(f,BLOCK_SIZE+n*16,SEEK_SET);  
       	fwrite(&file,sizeof(struct filelist),1,f);  
       	printf("文件已刪除!\n");  
    	}  
}  
void close_file(){
int k,n;  
    	char name[12];  
    	printf("輸入文件名:");  
    	scanf("%s",name);  
    	getchar();  
    	n=name_i(name);           
   	if(n==-1) 
printf("文件不存在或未打開\n");  
    	else{  
       		k=p->s_inode[n]-100;    
       		fd[k].t_node->f_node->used=0;     
       		fd[k].t_node->f_node=NULL;        
       		fd[k].t_node=NULL;                
       		p->s_inode[n]=0;        
       		printf("文件已關閉!\n");  
    	}  
}  
void myexit(){   
int i=0;  
    	char ch;  
    	while(fcb[i].used==0) i++;     
    	if(i<5){               
       		getchar();  
       		printf("一些文件仍處於打開狀態!!!\n");  
       		printf("輸入“q”或其他鍵返回\n");  
       		scanf("%c",&ch);  
       		if(ch=='q'){        
          		while(i<5){  
             			if(fcb[i].used==1) 
p->s_inode[fcb[i].inode_num]=0;  
             			i++;  
          		}  
         		fseek(f,0,SEEK_SET);  
         		fwrite(p,sizeof(struct filsys),1,f);  
         		exit(0);  
       		}  
       		getchar();  
    	}else{                 
       	fseek(f,0,SEEK_SET);  
       	fwrite(p,sizeof(struct filsys),1,f);  
       	exit(0);  
    	}  
}  
void main(){    
 	int i;  
    	char ch,sys_name[15];  
    	p=(struct filsys *)malloc(sizeof(struct filsys));    
    	while(1){  
       		printf("--------------1:創建新文件系統---------------\n"); 
       		printf("--------------2:打開已有的文件系統-----------\n");  
       		printf("請選擇:");  
       		if((ch=getchar())=='1'){         
          		printf("輸入文件系統名稱:");  
          		scanf("%s",sys_name);  
          		getchar();  
          		f=apply_room(sys_name);       
          		init();                       
          		break;          //這裏的break用來跳出while(1)的循環  
       		}  
 		else if(ch=='2'){              
          		printf("輸入文件系統名稱:"); 
          		scanf("%s",sys_name);  
          		getchar();  
          		f=fopen(sys_name,"r+b");  
          		fseek(f,0,SEEK_SET);  
          		fread(p,sizeof(struct filsys),1,f);      
          		break;  
       		}  
       		else{  
          		printf("輸入有誤!\n");  
          		getchar();  
       		}  
};  
 	for(i=0;i<5;i++){              
       	fcb[i].used=0;  
       	table[i].f_node=NULL;  
       	fd[i].t_node=NULL;  
    	}  
  	while(1){  
              	printf("-------------------------------------------------------------------------------------------------\n");  
              	printf("|~~~~~~~~~~~~~~~~~~~~~~1:新建文件~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");  
	  	printf("|~~~~~~~~~~~~~~~~~~~~~~2:打開文件~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
	   	printf("|~~~~~~~~~~~~~~~~~~~~~~3:編輯文件~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
	   	printf("|~~~~~~~~~~~~~~~~~~~~~~4:閱讀文件~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
	   	printf("|~~~~~~~~~~~~~~~~~~~~~~5:關閉文件~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
	   	printf("|~~~~~~~~~~~~~~~~~~~~~~6:刪除文件~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
	   	printf("|~~~~~~~~~~~~~~~~~~~~~~7:退        出~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
	   	printf("------------------------------------------------------------------------------------------------\n");  
       		printf("請選擇:");  
       		switch(getchar()-'0'){       
    			case 1:
create();
break;  
    			case 2:
open_file();
break;  
    			case 3:
write_file();
break;  
   			case 4:
read_file();
break;  
    			case 5:
close_file();
break;  
    			case 6:
del_file();
break;  
    			case 7:
myexit();
break;  
    			default:getchar(); 
printf("輸入有誤!\n"); break;  
       		}  
    	};  
    	free(p);  
    	fclose(f);  
}