1 /* 2 * Copyright (c) 1982, 1986, 1989 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms are permitted 6 * provided that the above copyright notice and this paragraph are 7 * duplicated in all such forms and that any documentation, 8 * advertising materials, and other materials related to such 9 * distribution and use acknowledge that the software was developed 10 * by the University of California, Berkeley. The name of the 11 * University may not be used to endorse or promote products derived 12 * from this software without specific prior written permission. 13 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED 15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 16 * 17 * @(#)dir.h 7.8 (Berkeley) 02/15/90 18 */ 19 20 #ifndef _DIR_ 21 #define _DIR_ 22 23 /* 24 * A directory consists of some number of blocks of DIRBLKSIZ 25 * bytes, where DIRBLKSIZ is chosen such that it can be transferred 26 * to disk in a single atomic operation (e.g. 512 bytes on most machines). 27 * 28 * Each DIRBLKSIZ byte block contains some number of directory entry 29 * structures, which are of variable length. Each directory entry has 30 * a struct direct at the front of it, containing its inode number, 31 * the length of the entry, and the length of the name contained in 32 * the entry. These are followed by the name padded to a 4 byte boundary 33 * with null bytes. All names are guaranteed null terminated. 34 * The maximum length of a name in a directory is MAXNAMLEN. 35 * 36 * The macro DIRSIZ(dp) gives the amount of space required to represent 37 * a directory entry. Free space in a directory is represented by 38 * entries which have dp->d_reclen > DIRSIZ(dp). All DIRBLKSIZ bytes 39 * in a directory block are claimed by the directory entries. This 40 * usually results in the last entry in a directory having a large 41 * dp->d_reclen. When entries are deleted from a directory, the 42 * space is returned to the previous entry in the same directory 43 * block by increasing its dp->d_reclen. If the first entry of 44 * a directory block is free, then its dp->d_ino is set to 0. 45 * Entries other than the first in a directory do not normally have 46 * dp->d_ino set to 0. 47 */ 48 #define DIRBLKSIZ DEV_BSIZE 49 #define MAXNAMLEN 255 50 51 struct direct { 52 u_long d_ino; /* inode number of entry */ 53 u_short d_reclen; /* length of this record */ 54 u_short d_namlen; /* length of string in d_name */ 55 char d_name[MAXNAMLEN + 1]; /* name with length <= MAXNAMLEN */ 56 }; 57 58 /* 59 * The DIRSIZ macro gives the minimum record length which will hold 60 * the directory entry. This requires the amount of space in struct direct 61 * without the d_name field, plus enough space for the name with a terminating 62 * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary. 63 */ 64 #define DIRSIZ(dp) \ 65 ((sizeof (struct direct) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3)) 66 67 /* 68 * Template for manipulating directories. 69 * Should use struct direct's, but the name field 70 * is MAXNAMLEN - 1, and this just won't do. 71 */ 72 struct dirtemplate { 73 u_long dot_ino; 74 short dot_reclen; 75 short dot_namlen; 76 char dot_name[4]; /* must be multiple of 4 */ 77 u_long dotdot_ino; 78 short dotdot_reclen; 79 short dotdot_namlen; 80 char dotdot_name[4]; /* ditto */ 81 }; 82 #endif /* _DIR_ */ 83