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Annotation of 42BSD/sys/h/dir.h, revision 1.1

1.1     ! root        1: /*     dir.h   6.1     83/07/29        */
        !             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: /* so user programs can just include dir.h */
        !            29: #if !defined(KERNEL) && !defined(DEV_BSIZE)
        !            30: #define        DEV_BSIZE       512
        !            31: #endif
        !            32: #define DIRBLKSIZ      DEV_BSIZE
        !            33: #define        MAXNAMLEN       255
        !            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
        !            72: 
        !            73: #ifdef KERNEL
        !            74: /*
        !            75:  * Template for manipulating directories.
        !            76:  * Should use struct direct's, but the name field
        !            77:  * is MAXNAMLEN - 1, and this just won't do.
        !            78:  */
        !            79: struct dirtemplate {
        !            80:        u_long  dot_ino;
        !            81:        short   dot_reclen;
        !            82:        short   dot_namlen;
        !            83:        char    dot_name[4];            /* must be multiple of 4 */
        !            84:        u_long  dotdot_ino;
        !            85:        short   dotdot_reclen;
        !            86:        short   dotdot_namlen;
        !            87:        char    dotdot_name[4];         /* ditto */
        !            88: };
        !            89: #endif

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