4.3BSD - /usr/src/new/mh/miscellany/libndir/dir.h

   1: /*	dir.h	4.4	82/07/25	*/
   2: 
   3: /*
   4:  * A directory consists of some number of blocks of DIRBLKSIZ
   5:  * bytes, where DIRBLKSIZ is chosen such that it can be transferred
   6:  * to disk in a single atomic operation (e.g. 512 bytes on most machines).
   7:  *
   8:  * Each DIRBLKSIZ byte block contains some number of directory entry
   9:  * structures, which are of variable length.  Each directory entry has
  10:  * a struct direct at the front of it, containing its inode number,
  11:  * the length of the entry, and the length of the name contained in
  12:  * the entry.  These are followed by the name padded to a 4 byte boundary
  13:  * with null bytes.  All names are guaranteed null terminated.
  14:  * The maximum length of a name in a directory is MAXNAMLEN.
  15:  *
  16:  * The macro DIRSIZ(dp) gives the amount of space required to represent
  17:  * a directory entry.  Free space in a directory is represented by
  18:  * entries which have dp->d_reclen >= DIRSIZ(dp).  All DIRBLKSIZ bytes
  19:  * in a directory block are claimed by the directory entries.  This
  20:  * usually results in the last entry in a directory having a large
  21:  * dp->d_reclen.  When entries are deleted from a directory, the
  22:  * space is returned to the previous entry in the same directory
  23:  * block by increasing its dp->d_reclen.  If the first entry of
  24:  * a directory block is free, then its dp->d_ino is set to 0.
  25:  * Entries other than the first in a directory do not normally have
  26:  * dp->d_ino set to 0.
  27:  */
  28: #define DIRBLKSIZ   512
  29: #define MAXNAMLEN   255
  30: 
  31: #ifdef pdp11
  32: #define u_long long
  33: #endif
  34: 
  35: struct  direct {
  36:     u_long  d_ino;          /* inode number of entry */
  37:     u_short d_reclen;       /* length of this record */
  38:     u_short d_namlen;       /* length of string in d_name */
  39:     char    d_name[MAXNAMLEN + 1];  /* name must be no longer than this */
  40: };
  41: 
  42: /*
  43:  * The DIRSIZ macro gives the minimum record length which will hold
  44:  * the directory entry.  This requires the amount of space in struct direct
  45:  * without the d_name field, plus enough space for the name with a terminating
  46:  * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary.
  47:  */
  48: #undef DIRSIZ
  49: #define DIRSIZ(dp) \
  50:     ((sizeof (struct direct) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3))
  51: 
  52: #ifndef KERNEL
  53: /*
  54:  * Definitions for library routines operating on directories.
  55:  */
  56: typedef struct _dirdesc {
  57:     int dd_fd;
  58:     long    dd_loc;
  59:     long    dd_size;
  60:     char    dd_buf[DIRBLKSIZ];
  61: } DIR;
  62: #ifndef NULL
  63: #define NULL 0
  64: #endif
  65: extern  DIR *opendir();
  66: extern  struct direct *readdir();
  67: extern  long telldir();
  68: extern  void seekdir();
  69: #define rewinddir(dirp) seekdir((dirp), (long)0)
  70: extern  void closedir();
  71: #endif KERNEL

Defined struct's

Defined typedef's

Defined macros