new format for prototypes; more precise comments

[unix-history] / usr / src / sys / ufs / ffs / dir.h

diff --git a/usr/src/sys/ufs/ffs/dir.h b/usr/src/sys/ufs/ffs/dir.h
index 33f0ea4..3b5160f 100644 (file)
--- a/usr/src/sys/ufs/ffs/dir.h
+++ b/usr/src/sys/ufs/ffs/dir.h
@@ -1,10 +1,72 @@
-/*     dir.h   3.2     %G%     */
-
-#ifndef        DIRSIZ
-#define        DIRSIZ  14
-#endif
-struct direct
-{
-       ino_t   d_ino;
-       char    d_name[DIRSIZ];
+/*
+ * Copyright (c) 1982, 1986, 1989 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * %sccs.include.redist.c%
+ *
+ *     @(#)dir.h       7.10 (Berkeley) %G%
+ */
+
+#ifndef _DIR_H_
+#define        _DIR_H_
+
+/*
+ * A directory consists of some number of blocks of DIRBLKSIZ
+ * bytes, where DIRBLKSIZ is chosen such that it can be transferred
+ * to disk in a single atomic operation (e.g. 512 bytes on most machines).
+ *
+ * Each DIRBLKSIZ byte block contains some number of directory entry
+ * structures, which are of variable length.  Each directory entry has
+ * a struct direct at the front of it, containing its inode number,
+ * the length of the entry, and the length of the name contained in
+ * the entry.  These are followed by the name padded to a 4 byte boundary
+ * with null bytes.  All names are guaranteed null terminated.
+ * The maximum length of a name in a directory is MAXNAMLEN.
+ *
+ * The macro DIRSIZ(dp) gives the amount of space required to represent
+ * a directory entry.  Free space in a directory is represented by
+ * entries which have dp->d_reclen > DIRSIZ(dp).  All DIRBLKSIZ bytes
+ * in a directory block are claimed by the directory entries.  This
+ * usually results in the last entry in a directory having a large
+ * dp->d_reclen.  When entries are deleted from a directory, the
+ * space is returned to the previous entry in the same directory
+ * block by increasing its dp->d_reclen.  If the first entry of
+ * a directory block is free, then its dp->d_ino is set to 0.
+ * Entries other than the first in a directory do not normally have
+ * dp->d_ino set to 0.
+ */
+#define DIRBLKSIZ      DEV_BSIZE
+#define        MAXNAMLEN       255
+
+struct direct {
+       u_long  d_ino;                  /* inode number of entry */
+       u_short d_reclen;               /* length of this record */
+       u_short d_namlen;               /* length of string in d_name */
+       char    d_name[MAXNAMLEN + 1];  /* name with length <= MAXNAMLEN */
+};
+
+/*
+ * The DIRSIZ macro gives the minimum record length which will hold
+ * the directory entry.  This requires the amount of space in struct direct
+ * without the d_name field, plus enough space for the name with a terminating
+ * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary.
+ */
+#define DIRSIZ(dp) \
+    ((sizeof (struct direct) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3))
+
+/*
+ * Template for manipulating directories.
+ * Should use struct direct's, but the name field
+ * is MAXNAMLEN - 1, and this just won't do.
+ */
+struct dirtemplate {
+       u_long  dot_ino;
+       short   dot_reclen;
+       short   dot_namlen;
+       char    dot_name[4];            /* must be multiple of 4 */
+       u_long  dotdot_ino;
+       short   dotdot_reclen;
+       short   dotdot_namlen;
+       char    dotdot_name[4];         /* ditto */

 };
 };

+#endif /* !_DIR_H_ */