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Annotation of 42BSD/usr.lib/sendmail/lib/libndir/dir.h, revision 1.1

1.1     ! root        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: struct direct {
        !            32:        u_long  d_ino;                  /* inode number of entry */
        !            33:        u_short d_reclen;               /* length of this record */
        !            34:        u_short d_namlen;               /* length of string in d_name */
        !            35:        char    d_name[MAXNAMLEN + 1];  /* name must be no longer than this */
        !            36: };
        !            37: 
        !            38: /*
        !            39:  * The DIRSIZ macro gives the minimum record length which will hold
        !            40:  * the directory entry.  This requires the amount of space in struct direct
        !            41:  * without the d_name field, plus enough space for the name with a terminating
        !            42:  * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary.
        !            43:  */
        !            44: #undef DIRSIZ
        !            45: #define DIRSIZ(dp) \
        !            46:     ((sizeof (struct direct) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3))
        !            47: 
        !            48: #ifndef KERNEL
        !            49: /*
        !            50:  * Definitions for library routines operating on directories.
        !            51:  */
        !            52: typedef struct _dirdesc {
        !            53:        int     dd_fd;
        !            54:        long    dd_loc;
        !            55:        long    dd_size;
        !            56:        char    dd_buf[DIRBLKSIZ];
        !            57: } DIR;
        !            58: #ifndef NULL
        !            59: #define NULL 0
        !            60: #endif
        !            61: extern DIR *opendir();
        !            62: extern struct direct *readdir();
        !            63: extern long telldir();
        !            64: extern void seekdir();
        !            65: #define rewinddir(dirp)        seekdir((dirp), (long)0)
        !            66: extern void closedir();
        !            67: #endif KERNEL

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