--- cci/usr/src/etc/dump/dumpitime.c	2019/07/28 12:24:19	1.1
+++ cci/usr/src/etc/dump/dumpitime.c	2019/07/28 12:24:33	1.1.1.2
@@ -1,4 +1,12 @@
-static	char *sccsid = "@(#)dumpitime.c	1.12 (Berkeley) 9/13/83";
+/*
+ * Copyright (c) 1980 Regents of the University of California.
+ * All rights reserved.  The Berkeley software License Agreement
+ * specifies the terms and conditions for redistribution.
+ */
+
+#ifndef lint
+static char sccsid[] = "@(#)dumpitime.c	5.1 (Berkeley) 6/5/85";
+#endif not lint
 
 #include "dump.h"
 #include <sys/file.h>
@@ -204,23 +212,36 @@ int makeidate(ip, buf)
 
 /*
  * This is an estimation of the number of TP_BSIZE blocks in the file.
+ * It estimates the number of blocks in files with holes by assuming
+ * that all of the blocks accounted for by di_blocks are data blocks
+ * (when some of the blocks are usually used for indirect pointers);
+ * hence the estimate may be high.
  */
 est(ip)
 	struct dinode *ip;
 {
 	long s, t;
 
+ 	/*
+ 	 * ip->di_size is the size of the file in bytes.
+ 	 * ip->di_blocks stores the number of sectors actually in the file.
+ 	 * If there are more sectors than the size would indicate, this just
+ 	 *	means that there are indirect blocks in the file or unused
+	 *	sectors in the last file block;	we can safely ignore these
+	 *	(s = t below).
+ 	 * If the file is bigger than the number of sectors would indicate,
+ 	 *	then the file has holes in it.  In this case we must use the
+ 	 *	block count to estimate the number of data blocks used, but
+ 	 *	we use the actual size for estimating the number of indirect
+ 	 *	dump blocks (t vs. s in the indirect block calculation).
+ 	 */
 	esize++;
-	/*
-	 * ip->di_size is the size of the file in bytes.
-	 * ip->di_blocks stores the number of sectors actually in the file.
-	 */
-	s = howmany(dbtob(ip->di_blocks), TP_BSIZE);
-	t = howmany(ip->di_size, TP_BSIZE);
-	if (s > t)
-		s = t;
+ 	s = howmany(dbtob(ip->di_blocks), TP_BSIZE);
+ 	t = howmany(ip->di_size, TP_BSIZE);
+ 	if ( s > t )
+ 		s = t;
 	if (ip->di_size > sblock->fs_bsize * NDADDR) {
-		/* calc number of indirect blocks on the dump tape */
+		/* calculate the number of indirect blocks on the dump tape */
 		s += howmany(t - NDADDR * sblock->fs_bsize / TP_BSIZE,
 			TP_NINDIR);
 	}