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 7.2 (Berkeley) 12/22/86 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 69 #define dirfd(dirp) ((dirp)->dd_fd) 70 71 #ifndef NULL 72 #define NULL 0 73 #endif 74 extern DIR *opendir(); 75 extern struct direct *readdir(); 76 extern long telldir(); 77 extern void seekdir(); 78 #define rewinddir(dirp) seekdir((dirp), (long)0) 79 extern void closedir(); 80 #endif 81 82 #ifdef KERNEL 83 /* 84 * Template for manipulating directories. 85 * Should use struct direct's, but the name field 86 * is MAXNAMLEN - 1, and this just won't do. 87 */ 88 struct dirtemplate { 89 u_long dot_ino; 90 short dot_reclen; 91 short dot_namlen; 92 char dot_name[4]; /* must be multiple of 4 */ 93 u_long dotdot_ino; 94 short dotdot_reclen; 95 short dotdot_namlen; 96 char dotdot_name[4]; /* ditto */ 97 }; 98 #endif 99