fs.h

   1 // On-disk file system format.
   2 // Both the kernel and user programs use this header file.
   3
   4 // Block 0 is unused.
   5 // Block 1 is super block.
   6 // Inodes start at block 2.
   7
   8 #define ROOTINO 1  // root i-number
   9 #define BSIZE 512  // block size
  10
  11 // File system super block
  12 struct superblock {
  13   uint size;         // Size of file system image (blocks)
  14   uint nblocks;      // Number of data blocks
  15   uint ninodes;      // Number of inodes.
  16 };
  17
  18 #define NDIRECT 12
  19 #define NINDIRECT (BSIZE / sizeof(uint))
  20 #define MAXFILE (NDIRECT + NINDIRECT)
  21
  22 // On-disk inode structure
  23 struct dinode {
  24   short type;           // File type
  25   short major;          // Major device number (T_DEV only)
  26   short minor;          // Minor device number (T_DEV only)
  27   short nlink;          // Number of links to inode in file system
  28   uint size;            // Size of file (bytes)
  29   uint addrs[NDIRECT+1];   // Data block addresses
  30 };
  31
  32 // Inodes per block.
  33 #define IPB           (BSIZE / sizeof(struct dinode))
  34
  35 // Block containing inode i
  36 #define IBLOCK(i)     ((i) / IPB + 2)
  37
  38 // Bitmap bits per block
  39 #define BPB           (BSIZE*8)
  40
  41 // Block containing bit for block b
  42 #define BBLOCK(b, ninodes) (b/BPB + (ninodes)/IPB + 3)
  43
  44 // Directory is a file containing a sequence of dirent structures.
  45 #define DIRSIZ 14
  46
  47 struct dirent {
  48   ushort inum;
  49   char name[DIRSIZ];
  50 };
  51