rdwt.c

操作系统实验,文件系统,c语言实现的

#include <stdio.h>

#include "filesys.h"

unsigned int read(fd1,buf,size)

int fd1;

char *buf;

unsigned int size;

{

    unsigned long off;

    int block,block_off,i,j;

    struct inode *inode;

    char *temp_buf;

       inode=sys_ofile[user[user_id].u_ofile[fd1]].f_inode;

printf("\nf_inode=%d\n",sys_ofile[user[user_id].u_ofile[fd1]].f_inode);

　

   if(! (sys_ofile[user[user_id].u_ofile[fd1]].f_flag&FREAD))

   {

       printf("\nthe file is not opened for read\n");

       return 0;

   }

       temp_buf=buf;

       off=sys_ofile[user[user_id].u_ofile[fd1]].f_off;

       if((off+size)>inode->di_size) size=inode->di_size-off;

  

       block_off=off%BLOCKSIZ;

       block=off/BLOCKSIZ;

       if(block-off+size<BLOCKSIZ)

   {

       fseek(fd,DATASTART+inode->di_addr[block]*BLOCKSIZ+block_off,SEEK_SET);

       fread(buf,1,size,fd);

           return size;

    }

   fseek(fd,DATASTART+inode->di_addr[block]*BLOCKSIZ+block_off,SEEK_SET);

   fread(temp_buf,1,BLOCKSIZ-block_off,fd);

   temp_buf+=BLOCKSIZ-block_off;

   j=(inode->di_size-off-block_off)/BLOCKSIZ;

   for(i=0;i<(size-block_off)/BLOCKSIZ;i++)

   {

   fseek(fd,DATASTART+inode->di_addr[j+i]*BLOCKSIZ,SEEK_SET);

   fread(temp_buf,1,BLOCKSIZ,fd);

   temp_buf+=BLOCKSIZ;

   }

   block_off=(size-block_off)%BLOCKSIZ;

   block=inode->di_addr[off+size/BLOCKSIZ+1];

   fseek(fd,DATASTART+block*BLOCKSIZ,SEEK_SET);

   fread(temp_buf,1,block_off,fd);

   sys_ofile[user[user_id].u_ofile[fd1]].f_off+=size;

   return size;

   }

 

unsigned int write(fd1,buf,size)    /*write*/

unsigned short fd1;

char  *buf;

unsigned int size;

{

 unsigned long off;

 int block,block_off,i,j, k=0;

 struct inode *inode;

 char *temp_buf;

printf("\nf_off=%d\n",sys_ofile[user[user_id].u_ofile[fd1]].f_off); 

 inode=sys_ofile[user[user_id].u_ofile[fd1]].f_inode;

 printf("\ndi_size=%d,i_ino=%d\n",inode->di_size,inode->i_ino); 

 /*if(! (sys_ofile[user[user_id].u_ofile[fd1]].f_flag & FWRITE))

 {

   printf("\nthe file is not opened for wrie\n");

   return 0;

 }

*/

  temp_buf=buf;

 off=sys_ofile[user[user_id].u_ofile[fd1]].f_off;

 block_off=off%BLOCKSIZ;

 block=off/BLOCKSIZ;

 if(block_off+size<BLOCKSIZ)

 {

   fseek(fd,DATASTART+inode->di_addr[block]* BLOCKSIZ+block_off,SEEK_SET);

   fwrite(buf,1,size,fd);

   return size;

 }

　

  if(sys_ofile[user[user_id].u_ofile[fd1]].f_flag == FAPPEND) 

{ 

fseek(fd,DATASTART+inode->di_addr[block]*BLOCKSIZ+block_off,SEEK_SET); 

 fwrite(temp_buf,1,BLOCKSIZ-block_off,fd); 

 temp_buf+=BLOCKSIZ-block_off; 

 k=1; 

} 

 printf("\nsize=%d,block_off=%d\n",size,block_off); 

 for(i=0;i<(size-k*(BLOCKSIZ-block_off))/BLOCKSIZ;i++)

 {

   inode->di_addr[block+i]=balloc();

   fseek(fd,DATASTART+inode->di_addr[block+k+i]*BLOCKSIZ,SEEK_SET);

   fwrite(temp_buf,1,BLOCKSIZ,fd);

   temp_buf+=BLOCKSIZ;

 }

   block_off=(size-k*(BLOCKSIZ-block_off))%BLOCKSIZ;

   block=inode->di_addr[block+k+i]=balloc();

   fseek(fd,DATASTART+block*BLOCKSIZ,SEEK_SET);

   fwrite(temp_buf,1,block_off,fd);

   sys_ofile[user[user_id].u_ofile[fd1]].f_off+=size;

 inode->di_size=sys_ofile[user[user_id].u_ofile[fd1]].f_off; 

   return size;

 }