1 /* ndir.h 4.4 82/07/25 */ 2 3 /* 4 * Change notice (rti!trt): To be compatible with non-bsd systems: 5 * #defines for u_short, u_long, and void added. 6 */ 7 8 #define u_short unsigned short 9 #define u_long long 10 #define void 11 12 /* 13 * A directory consists of some number of blocks of DIRBLKSIZ 14 * bytes, where DIRBLKSIZ is chosen such that it can be transferred 15 * to disk in a single atomic operation (e.g. 512 bytes on most machines). 16 * 17 * Each DIRBLKSIZ byte block contains some number of directory entry 18 * structures, which are of variable length. Each directory entry has 19 * a struct direct at the front of it, containing its inode number, 20 * the length of the entry, and the length of the name contained in 21 * the entry. These are followed by the name padded to a 4 byte boundary 22 * with null bytes. All names are guaranteed null terminated. 23 * The maximum length of a name in a directory is MAXNAMLEN. 24 * 25 * The macro DIRSIZ(dp) gives the amount of space required to represent 26 * a directory entry. Free space in a directory is represented by 27 * entries which have dp->d_reclen >= DIRSIZ(dp). All DIRBLKSIZ bytes 28 * in a directory block are claimed by the directory entries. This 29 * usually results in the last entry in a directory having a large 30 * dp->d_reclen. When entries are deleted from a directory, the 31 * space is returned to the previous entry in the same directory 32 * block by increasing its dp->d_reclen. If the first entry of 33 * a directory block is free, then its dp->d_ino is set to 0. 34 * Entries other than the first in a directory do not normally have 35 * dp->d_ino set to 0. 36 */ 37 #define DIRBLKSIZ 512 38 #define MAXNAMLEN 255 39 40 struct direct { 41 u_long d_ino; /* inode number of entry */ 42 u_short d_reclen; /* length of this record */ 43 u_short d_namlen; /* length of string in d_name */ 44 char d_name[MAXNAMLEN + 1]; /* name must be no longer than this */ 45 }; 46 47 /* 48 * The DIRSIZ macro gives the minimum record length which will hold 49 * the directory entry. This requires the amount of space in struct direct 50 * without the d_name field, plus enough space for the name with a terminating 51 * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary. 52 */ 53 #undef DIRSIZ 54 #define DIRSIZ(dp) \ 55 ((sizeof (struct direct) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3)) 56 57 #ifndef KERNEL 58 /* 59 * Definitions for library routines operating on directories. 60 */ 61 typedef struct _dirdesc { 62 int dd_fd; 63 long dd_loc; 64 long dd_size; 65 char dd_buf[DIRBLKSIZ]; 66 } DIR; 67 #ifndef NULL 68 #define NULL 0 69 #endif 70 extern DIR *opendir(); 71 extern struct direct *readdir(); 72 extern long telldir(); 73 extern void seekdir(); 74 #define rewinddir(dirp) seekdir((dirp), (long)0) 75 extern void closedir(); 76 #endif KERNEL 77