inode.c

模拟linux的ext3文件系统。采用位图法。用一个文件模拟硬盘。实现创建、删除目录、文件。读、写文件

#include"structure.h"
u16 new_inode()
{
 u16 ret;
 u8 i,j;
 u8 a,b;
 u8 buffer[512];
 fseek(FS,INODE_BITMAP,SEEK_SET);
 fread(buffer,sizeof(u8),512,FS);
 b=0;
 for(i=0;i<512;i++){
     a=b^buffer[i];
     if(a!=0xff)  break;
 }
 if(i==512)  ret=0;
 else{
     for(j=0;j<8;j++){
              a=pow(2,(7-j));
              b=a|buffer[i];
              if(b!=buffer[i]) break;
     }
     buffer[i]=b;
     fseek(FS,INODE_BITMAP,SEEK_SET);
     fwrite(buffer,sizeof(u8),512,FS);     
     ret=i*8+j;
 }    
 // if(ret)  update_inode_entry(&inode,ret);
 return ret;
}

void free_inode(u16 inode)
{
 u8 i,j,temp;
 u8 buffer[512];
 fseek(FS,INODE_BITMAP,SEEK_SET);
 fread(buffer,sizeof(u8),512,FS);
 i=inode/8;
 j=inode%8;
 temp=pow(2,(7-j));
 buffer[i]=temp^buffer[i];
 fseek(FS,INODE_BITMAP,SEEK_SET);
 fwrite(buffer,sizeof(u8),512,FS);
 fclose(FS);
 FS=fopen("FS","r+");
}


u16 test_inode(u16 inode)
{
 u8 i,j,a,b;
 u8 buffer[512];
 fseek(FS,INODE_BITMAP,SEEK_SET);
 fread(buffer,sizeof(u8),512,FS);
 i=inode/8;
 j=inode%8;
 a=pow(2,(7-j));
 b=a|buffer[i];
 if(b!=buffer[i])  return 0;
 return 1;
}


int update_group_desc(struct ext2_group_desc *group_desc)
{
 u8 buffer[512]={0,};
 buffer[16]=group_desc->bg_block_bitmap;
 buffer[18]=group_desc->bg_inode_bitmap;
 buffer[20]=group_desc->bg_inode_table;
 buffer[22]=group_desc->bg_free_blocks_count%0x100;
 buffer[23]=group_desc->bg_free_blocks_count/0x100;
 buffer[24]=group_desc->bg_free_inodes_count%0x100;
 buffer[25]=group_desc->bg_free_inodes_count/0x100;
 buffer[26]=group_desc->bg_used_dirs_count%0x100;
 buffer[27]=group_desc->bg_used_dirs_count/0x100;
 fseek(FS,0,SEEK_SET);
 fwrite(buffer,sizeof(u8),512,FS);
 fclose(FS);
 FS=fopen("FS","r+");
 return 1;
}
int reload_group_desc(struct ext2_group_desc *group_desc)
{
 u8 i;
 u8 buffer[512];
 if(FS==NULL) printf("FS not exits or not format \n");
 fseek(FS,0,SEEK_SET);
 fread(buffer,sizeof(u8),512,FS);
 for(i=0;i<16;i++)  group_desc->bg_volume_name[i]=buffer[i];
 group_desc->bg_block_bitmap=buffer[16];
 group_desc->bg_inode_bitmap=buffer[18];
 group_desc->bg_inode_table=buffer[20];
 group_desc->bg_free_blocks_count=buffer[23]*0x100+buffer[22];
 group_desc->bg_free_inodes_count=buffer[25]*0x100+buffer[24];
 group_desc->bg_used_dirs_count=buffer[26];
 return 1;
}

int load_inode_entry(struct ext2_inode *inode,u16 num_inode)
{
 u8  i;
 u8  buffer[512];
 u32 addr_inode;
 addr_inode=INODE_TABLE+num_inode*64;
 fseek(FS,addr_inode,SEEK_SET);
 fread(buffer,sizeof(u8),512,FS);
 inode->i_mode=buffer[1]*0x100+buffer[0];
 inode->i_blocks=buffer[3]*0x100+buffer[2];
 inode->i_size=buffer[7]*0x1000000+buffer[6]*0x10000+buffer[5]*0x100+buffer[4];
 inode->i_atime=buffer[11]*0x1000000+buffer[10]*0x10000+buffer[9]*0x100+buffer[8];
 inode->i_ctime=buffer[15]*0x1000000+buffer[14]*0x10000+buffer[13]*0x100+buffer[12];
 inode->i_mtime=buffer[19]*0x1000000+buffer[18]*0x10000+buffer[17]*0x100+buffer[16];
 inode->i_dtime=buffer[23]*0x1000000+buffer[22]*0x10000+buffer[21]*0x100+buffer[20];
 for(i=0;i<8;i++)          inode->i_block[i]=buffer[24+i*2+1]*0x100+buffer[24+i*2];
 return 1;
}

int update_inode_entry(struct ext2_inode *inode,u16 num_inode)
{
 u8 i;
 u8 buffer[512];
 u32 addr_inode;
 addr_inode=INODE_TABLE+num_inode*64;
 buffer[0]=inode->i_mode%0x100;
 buffer[1]=inode->i_mode/0x100;
 buffer[2]=inode->i_blocks%0x100;
 buffer[3]=inode->i_blocks/0x100;
 buffer[4]=inode->i_size%0x100;
 buffer[5]=(inode->i_size%0x10000)/0x100;
 buffer[6]=(inode->i_size%0x1000000)/0x10000;
 buffer[7]=(inode->i_size%0x100000000)/0x1000000;
 buffer[8]=inode->i_atime%0x100;
 buffer[9]=(inode->i_atime%0x10000)/0x100;
 buffer[10]=(inode->i_atime%0x1000000)/0x10000;
 buffer[11]=(inode->i_atime%0x100000000)/0x1000000;
 buffer[12]=inode->i_ctime%0x100;
 buffer[13]=(inode->i_ctime%0x10000)/0x100;
 buffer[14]=(inode->i_ctime%0x1000000)/0x10000;
 buffer[15]=(inode->i_ctime%0x100000000)/0x1000000;
 buffer[16]=inode->i_mtime%0x100;
 buffer[17]=(inode->i_mtime%0x10000)/0x100;
 buffer[18]=(inode->i_mtime%0x1000000)/0x10000;
 buffer[19]=(inode->i_mtime%0x100000000)/0x1000000;
 buffer[20]=inode->i_dtime%0x100;
 buffer[21]=(inode->i_dtime%0x10000)/0x100;
 buffer[22]=(inode->i_dtime%0x1000000)/0x10000;
 buffer[23]=(inode->i_dtime%0x100000000)/0x1000000;
 for(i=0;i<8;i++)  {buffer[24+i*2]=inode->i_block[i]%0x100; buffer[24+i*2+1]=inode->i_block[i]/0x100;}
 fseek(FS,addr_inode,SEEK_SET);
 fwrite(buffer,sizeof(u8),512,FS);
 fclose(FS);
 FS=fopen("FS","r+");
 
 return 1;
}