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Annotation of 43BSD/sys/h/dir.h, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1982, 1986 Regents of the University of California.
                      3:  * All rights reserved.  The Berkeley software License Agreement
                      4:  * specifies the terms and conditions for redistribution.
                      5:  *
                      6:  *     @(#)dir.h       7.1 (Berkeley) 6/4/86
                      7:  */
                      8: 
                      9: /*
                     10:  * A directory consists of some number of blocks of DIRBLKSIZ
                     11:  * bytes, where DIRBLKSIZ is chosen such that it can be transferred
                     12:  * to disk in a single atomic operation (e.g. 512 bytes on most machines).
                     13:  *
                     14:  * Each DIRBLKSIZ byte block contains some number of directory entry
                     15:  * structures, which are of variable length.  Each directory entry has
                     16:  * a struct direct at the front of it, containing its inode number,
                     17:  * the length of the entry, and the length of the name contained in
                     18:  * the entry.  These are followed by the name padded to a 4 byte boundary
                     19:  * with null bytes.  All names are guaranteed null terminated.
                     20:  * The maximum length of a name in a directory is MAXNAMLEN.
                     21:  *
                     22:  * The macro DIRSIZ(dp) gives the amount of space required to represent
                     23:  * a directory entry.  Free space in a directory is represented by
                     24:  * entries which have dp->d_reclen > DIRSIZ(dp).  All DIRBLKSIZ bytes
                     25:  * in a directory block are claimed by the directory entries.  This
                     26:  * usually results in the last entry in a directory having a large
                     27:  * dp->d_reclen.  When entries are deleted from a directory, the
                     28:  * space is returned to the previous entry in the same directory
                     29:  * block by increasing its dp->d_reclen.  If the first entry of
                     30:  * a directory block is free, then its dp->d_ino is set to 0.
                     31:  * Entries other than the first in a directory do not normally have
                     32:  * dp->d_ino set to 0.
                     33:  */
                     34: /* so user programs can just include dir.h */
                     35: #if !defined(KERNEL) && !defined(DEV_BSIZE)
                     36: #define        DEV_BSIZE       512
                     37: #endif
                     38: #define DIRBLKSIZ      DEV_BSIZE
                     39: #define        MAXNAMLEN       255
                     40: 
                     41: struct direct {
                     42:        u_long  d_ino;                  /* inode number of entry */
                     43:        u_short d_reclen;               /* length of this record */
                     44:        u_short d_namlen;               /* length of string in d_name */
                     45:        char    d_name[MAXNAMLEN + 1];  /* name must be no longer than this */
                     46: };
                     47: 
                     48: /*
                     49:  * The DIRSIZ macro gives the minimum record length which will hold
                     50:  * the directory entry.  This requires the amount of space in struct direct
                     51:  * without the d_name field, plus enough space for the name with a terminating
                     52:  * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary.
                     53:  */
                     54: #undef DIRSIZ
                     55: #define DIRSIZ(dp) \
                     56:     ((sizeof (struct direct) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3))
                     57: 
                     58: #ifndef KERNEL
                     59: /*
                     60:  * Definitions for library routines operating on directories.
                     61:  */
                     62: typedef struct _dirdesc {
                     63:        int     dd_fd;
                     64:        long    dd_loc;
                     65:        long    dd_size;
                     66:        char    dd_buf[DIRBLKSIZ];
                     67: } DIR;
                     68: #ifndef NULL
                     69: #define NULL 0
                     70: #endif
                     71: extern DIR *opendir();
                     72: extern struct direct *readdir();
                     73: extern long telldir();
                     74: extern void seekdir();
                     75: #define rewinddir(dirp)        seekdir((dirp), (long)0)
                     76: extern void closedir();
                     77: #endif
                     78: 
                     79: #ifdef KERNEL
                     80: /*
                     81:  * Template for manipulating directories.
                     82:  * Should use struct direct's, but the name field
                     83:  * is MAXNAMLEN - 1, and this just won't do.
                     84:  */
                     85: struct dirtemplate {
                     86:        u_long  dot_ino;
                     87:        short   dot_reclen;
                     88:        short   dot_namlen;
                     89:        char    dot_name[4];            /* must be multiple of 4 */
                     90:        u_long  dotdot_ino;
                     91:        short   dotdot_reclen;
                     92:        short   dotdot_namlen;
                     93:        char    dotdot_name[4];         /* ditto */
                     94: };
                     95: #endif

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