1 /* dir.h 4.5 82/11/13 */ 2 3 /* 4 * A directory consists of some number of blocks of DIRBLKSIZ 5 * bytes, where DIRBLKSIZ is chosen such that it can be transferred 6 * to disk in a single atomic operation (e.g. 512 bytes on most machines). 7 * 8 * Each DIRBLKSIZ byte block contains some number of directory entry 9 * structures, which are of variable length. Each directory entry has 10 * a struct direct at the front of it, containing its inode number, 11 * the length of the entry, and the length of the name contained in 12 * the entry. These are followed by the name padded to a 4 byte boundary 13 * with null bytes. All names are guaranteed null terminated. 14 * The maximum length of a name in a directory is MAXNAMLEN. 15 * 16 * The macro DIRSIZ(dp) gives the amount of space required to represent 17 * a directory entry. Free space in a directory is represented by 18 * entries which have dp->d_reclen > DIRSIZ(dp). All DIRBLKSIZ bytes 19 * in a directory block are claimed by the directory entries. This 20 * usually results in the last entry in a directory having a large 21 * dp->d_reclen. When entries are deleted from a directory, the 22 * space is returned to the previous entry in the same directory 23 * block by increasing its dp->d_reclen. If the first entry of 24 * a directory block is free, then its dp->d_ino is set to 0. 25 * Entries other than the first in a directory do not normally have 26 * dp->d_ino set to 0. 27 */ 28 /* so user programs can just include dir.h */ 29 #if !defined(KERNEL) && !defined(DEV_BSIZE) 30 #define DEV_BSIZE 512 31 #endif 32 #define DIRBLKSIZ DEV_BSIZE 33 #define MAXNAMLEN 255 34 35 struct direct { 36 u_long d_ino; /* inode number of entry */ 37 u_short d_reclen; /* length of this record */ 38 u_short d_namlen; /* length of string in d_name */ 39 char d_name[MAXNAMLEN + 1]; /* name must be no longer than this */ 40 }; 41 42 /* 43 * The DIRSIZ macro gives the minimum record length which will hold 44 * the directory entry. This requires the amount of space in struct direct 45 * without the d_name field, plus enough space for the name with a terminating 46 * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary. 47 */ 48 #undef DIRSIZ 49 #define DIRSIZ(dp) \ 50 ((sizeof (struct direct) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3)) 51 52 #ifndef KERNEL 53 /* 54 * Definitions for library routines operating on directories. 55 */ 56 typedef struct _dirdesc { 57 int dd_fd; 58 long dd_loc; 59 long dd_size; 60 char dd_buf[DIRBLKSIZ]; 61 } DIR; 62 #ifndef NULL 63 #define NULL 0 64 #endif 65 extern DIR *opendir(); 66 extern struct direct *readdir(); 67 extern long telldir(); 68 extern void seekdir(); 69 #define rewinddir(dirp) seekdir((dirp), (long)0) 70 extern void closedir(); 71 #endif 72 73 #ifdef KERNEL 74 /* 75 * Template for manipulating directories. 76 * Should use struct direct's, but the name field 77 * is MAXNAMLEN - 1, and this just won't do. 78 */ 79 struct dirtemplate { 80 u_long dot_ino; 81 short dot_reclen; 82 short dot_namlen; 83 char dot_name[4]; /* must be multiple of 4 */ 84 u_long dotdot_ino; 85 short dotdot_reclen; 86 short dotdot_namlen; 87 char dotdot_name[4]; /* ditto */ 88 }; 89 #endif 90