minix/include/dirent.h

/*	dirent.h - Declarations for directory reading routines.
 *							Author: Kees J. Bot
 *								24 Apr 1989
 * 
 * Note: The V7 format directory entries used under Minix must be transformed
 * into a struct dirent with a d_name of at least 15 characters.  Given that
 * we have to transform V7 entries anyhow it is little trouble to let the
 * routines understand the so-called "flex" directory format too.
 */

#ifndef _DIRENT_H
#define _DIRENT_H

#ifndef _TYPES_H
#include <sys/types.h>
#endif

#include <sys/dir.h>

/* _fl_direct is a flexible directory entry.  Actually it's a union of 8
 * characters and the 3 fields defined below. 
 */

/* Flexible directory entry: */
struct _fl_direct {		/* First slot in an entry */
	ino_t		d_ino;
	unsigned char	d_extent;
	char		d_name[3];  /* two characters for the shortest name */
};

	/* Name of length len needs _EXTENT(len) extra slots. */
#define _EXTENT(len)	(((len) + 5) >> 3)

/* Version 7 directory entry: */
struct _v7_direct {		
	ino_t		d_ino;
	char		d_name[DIRSIZ];
};

/* The block size must be at least 1024 bytes, because otherwise
 * the superblock (at 1024 bytes) overlaps with other filesystem data.
 */
#define MIN_BLOCK_SIZE		 1024

/* The below is allocated in some parts of the system as the largest
 * a filesystem block can be. For instance, the boot monitor allocates
 * 3 of these blocks and has to fit within 64kB, so this can't be
 * increased without taking that into account.
 */
#define MAX_BLOCK_SIZE		 8192

/* This is the block size for the fixed versions of the filesystem (V1/V2) */
#define STATIC_BLOCK_SIZE	1024

#define STATIC_FLEX_PER_BLOCK (STATIC_BLOCK_SIZE/sizeof(struct _fl_direct))
#define FLEX_PER_V7 (_EXTENT(DIRSIZ) + 1)
#define FLEX_PER_BLOCK (STATIC_BLOCK_SIZE/sizeof(struct _fl_direct))

/* Definitions for the directory(3) routines: */
typedef struct {
	char		_fd;	/* Filedescriptor of open directory */
	char		_v7;	/* Directory is Version 7 */
	short		_count;	/* This many objects in buf */
	off_t		_pos;	/* Position in directory file */
	struct _fl_direct  *_ptr;	/* Next slot in buf */
	struct _fl_direct  _buf[FLEX_PER_BLOCK]; /* One block of a directory file */
	struct _fl_direct  _v7f[FLEX_PER_V7];	 /* V7 entry transformed to flex */
} DIR;

struct dirent {		/* Largest entry (8 slots) */
	ino_t		d_ino;		/* I-node number */
	unsigned char	d_extent;	/* Extended with this many slots */
	char		d_name[61];	/* Null terminated name */
};

/* Function Prototypes. */
_PROTOTYPE( int closedir, (DIR *_dirp)					);
_PROTOTYPE( DIR *opendir, (const char *_dirname)			);
_PROTOTYPE( struct dirent *readdir, (DIR *_dirp)			);
_PROTOTYPE( void rewinddir, (DIR *_dirp)				);

#ifdef _MINIX
_PROTOTYPE( int seekdir, (DIR *_dirp, off_t _loc)			);
_PROTOTYPE( off_t telldir, (DIR *_dirp)					);
#endif

#endif /* _DIRENT_H */