1 /* 2 * Copyright (c) 1982, 1986, 1989 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 * 7 * @(#)dir.h 7.10 (Berkeley) 03/25/91 8 */ 9 10 #ifndef _DIR_H_ 11 #define _DIR_H_ 12 13 /* 14 * A directory consists of some number of blocks of DIRBLKSIZ 15 * bytes, where DIRBLKSIZ is chosen such that it can be transferred 16 * to disk in a single atomic operation (e.g. 512 bytes on most machines). 17 * 18 * Each DIRBLKSIZ byte block contains some number of directory entry 19 * structures, which are of variable length. Each directory entry has 20 * a struct direct at the front of it, containing its inode number, 21 * the length of the entry, and the length of the name contained in 22 * the entry. These are followed by the name padded to a 4 byte boundary 23 * with null bytes. All names are guaranteed null terminated. 24 * The maximum length of a name in a directory is MAXNAMLEN. 25 * 26 * The macro DIRSIZ(dp) gives the amount of space required to represent 27 * a directory entry. Free space in a directory is represented by 28 * entries which have dp->d_reclen > DIRSIZ(dp). All DIRBLKSIZ bytes 29 * in a directory block are claimed by the directory entries. This 30 * usually results in the last entry in a directory having a large 31 * dp->d_reclen. When entries are deleted from a directory, the 32 * space is returned to the previous entry in the same directory 33 * block by increasing its dp->d_reclen. If the first entry of 34 * a directory block is free, then its dp->d_ino is set to 0. 35 * Entries other than the first in a directory do not normally have 36 * dp->d_ino set to 0. 37 */ 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 with length <= MAXNAMLEN */ 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 #define DIRSIZ(dp) \ 55 ((sizeof (struct direct) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3)) 56 57 /* 58 * Template for manipulating directories. 59 * Should use struct direct's, but the name field 60 * is MAXNAMLEN - 1, and this just won't do. 61 */ 62 struct dirtemplate { 63 u_long dot_ino; 64 short dot_reclen; 65 short dot_namlen; 66 char dot_name[4]; /* must be multiple of 4 */ 67 u_long dotdot_ino; 68 short dotdot_reclen; 69 short dotdot_namlen; 70 char dotdot_name[4]; /* ditto */ 71 }; 72 #endif /* !_DIR_H_ */ 73