paxdir.h

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/*
	<dirent.h> -- definitions for SVR3 directory access routines

	last edit:	25-Apr-1987	D A Gwyn

	Prerequisite:	<sys/types.h>
*/

#ifndef _PAX_DIRENT_H
#define _PAX_DIRENT_H

#include "config.h"
#ifdef USG
#define UFS
#else
#ifdef BSD
#define BFS
#endif
#endif

struct dirent { 			/* data from getdents()/readdir() */
    long		d_ino;		/* inode number of entry */
    off_t		d_off;		/* offset of disk directory entry */
    unsigned short	d_reclen;	/* length of this record */
    char		d_name[1];	/* name of file (non-POSIX) */
};

typedef struct {
    int		dd_fd;			/* file descriptor */
    int		dd_loc;			/* offset in block */
    int		dd_size;		/* amount of valid data */
    char	*dd_buf;		/* -> directory block */
} DIR;					/* stream data from opendir() */


/* 
 * The following nonportable ugliness could have been avoided by defining
 * DIRENTSIZ and DIRENTBASESIZ to also have (struct dirent *) arguments. 
 */
#define	DIRENTBASESIZ		(((struct dirent *)0)->d_name \
				- (char *)&((struct dirent *)0)->d_ino)
#define	DIRENTSIZ( namlen )	((DIRENTBASESIZ + sizeof(long) + (namlen)) \
				/ sizeof(long) * sizeof(long))

#define	MAXNAMLEN 512			/* maximum filename length */

#ifndef NAME_MAX
#define	NAME_MAX (MAXNAMLEN - 1)	/* DAG -- added for POSIX */
#endif

#define	DIRBUF	 8192			/* buffer size for fs-indep. dirs */
		/* must in general be larger than the filesystem buffer size */

extern DIR		*opendir();
extern struct dirent	*readdir();
extern OFFSET		telldir();
extern void		seekdir();
extern int		closedir();

#endif /* _PAX_DIRENT_H */