d-super-block.c

用于汇编领域的,运用于OS的MAIN函数.基于硬件基础的源代码

//fs
struct d_super_block{};
char d_ibm[512]; // handle 511 inodes
char d_dbm[512]; // handle 512 blocks. 1 block=512 byte
struct d_inode { // each inode has 32 bytes.
   long blk[8]; // max 8 blocks per file
};
struct d_inode d_itable[16]; // 16 inodes in inode table
                             // but we don't use inode 0,1
struct dir_ent{ // directory entry. 16 bytes per entry
   long ino: // 4 bytes for inode number
   char fname[12]; // 12 bytes for file name
};
struct dir_block{ // max 32 entry per dir file
   struct dir_ent entries[32];
};

// functions for ibm
void init_d_ibm(){
   d_ibm[0]=1; // we reserve inode 0
   d_ibm[1]=1; // we reserve inode 1 
}

int get_free_inode(){// find free inode 
   int i;
   for(i=0;i<512;i++) // 
      if (d_ibm[i]==0) {
		  return i;
	  }
   panic("no more inode");
}
void set_inode_in_ibm(int x){
   d_ibm[x]=1;
}

// functions for dbm
void init_d_dbm(){
// block 0: boot code, blk 1: super block, blk 2: ibm, blk 3: dbm
// blk 4: inode table, blk 5: root dir
   d_dbm[0]=d_dbm[1]=d_dbm[2]=d_dbm[3]=d_dbm[4]=d_dbm[5]=1;
}

int get_free_block(){// find free block 
   int i;
   for(i=0;i<512;i++)
      if (d_dbm[i]==0) {
		  return i;
	  }
   panic("no more block");
}
void set_block_in_dbm(int x){
   d_dbm[x]=1;
}

// functions for directory
int get_free_dir_ent(struct dir_block *d){
// get free entry in directory block d
   int i;
   for(i=0;i<32;i++)
      if (empty_dir_ent(&(d->entries[i])))
	      return i;
   panic("no more entry in dir_ent");
}
int empty_dir_ent(struct dir_ent *dent){
   if (dent->ino==0)
      return 1;
   else return 0;
}

// functions for inode
struct d_inode init_root_inode(){
   struct d_inode r;
   // root dir has . and .. whose inode is 2 both.
   r.blk[0]=5;
   return r;
}

// functions for d_itable
void init_ditable(){
// inode 0,1 is reserved. inode 2 is for root dir
   d_itable[2]=init_root_inode();
}

// functions for directory
struct dir_block  make_empty_dir_block(int me, int parent){
// make empty dir block. me is this dir's inode; parent its parent inode
   struct dir_block blk;
   strcpy(blk->entries[0].fname, ".");
   blk->entries[0].ino=me;
   strcpy(blk->entries[1].fname, "..");
   blk->entries[1].ino=parent;
   return blk;
}

// system functions
   
void format_disk(){
// format disk
   struct dir_block rdir;
   wait_for_disk_insertion();
   init_d_ibm();
   init_d_dbm();
   init_d_itable();
   rdir=make_empty_dir_block(2,2);
   WriteRelativeSector(2, d_ibm, d_ibm);
   WriteRelativeSector(3, d_dbm, d_dbm);
   WriteRelativeSector(4, (char *)d_itable, (char *)d_itable);
   WriteRelativeSector(5, (char *)&rdir, (char *)&rdir);
}