From 719cd63d24412b338d315812f94c2a8f7114c656 Mon Sep 17 00:00:00 2001
From: lukem <lukem@NetBSD.org>
Date: Sun, 9 May 1999 13:48:44 +0000
Subject: [PATCH] Implement format_bytes(), which pretty prints a given
 u_int64_t into a given buffer, and if necessary, reducing the display width
 of the number to fit in the buffer by increasing the units (from kilobytes
 (2^10) through to exabytes (2^60)).

---
 sys/kern/kern_subr.c | 47 +++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 44 insertions(+), 3 deletions(-)

diff --git a/sys/kern/kern_subr.c b/sys/kern/kern_subr.c
index 135638458eb9..b2b3ac82b3bd 100644
--- a/sys/kern/kern_subr.c
+++ b/sys/kern/kern_subr.c
@@ -1,12 +1,12 @@
-/*	$NetBSD: kern_subr.c,v 1.47 1999/04/21 02:37:07 mrg Exp $	*/
+/*	$NetBSD: kern_subr.c,v 1.48 1999/05/09 13:48:44 lukem Exp $	*/
 
 /*-
- * Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
+ * Copyright (c) 1997, 1998, 1999 The NetBSD Foundation, Inc.
  * All rights reserved.
  *
  * This code is derived from software contributed to The NetBSD Foundation
  * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
- * NASA Ames Research Center.
+ * NASA Ames Research Center, and by Luke Mewburn.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -950,3 +950,44 @@ getstr(cp, size)
 		}
 	}
 }
+
+/*
+ * snprintf() `bytes' into `buf', reformatting it so that the number
+ * (plus a possible `xB' extension) fits into len bytes (including the
+ * terminating NUL).  Returns the number of bytes stored in buf, or -1
+ * if there was a problem.  E.g, given a len of 9: 
+ *	bytes		result
+ *	-----		------
+ *	99999		`99999'
+ *	100000		`97 KB'
+ *	66715648	`65152 KB'
+ *	252215296	`240 MB'
+ */
+int
+format_bytes(buf, len, bytes)
+	char		*buf;
+	size_t		 len;
+	u_int64_t	 bytes;
+{
+		/* prefixes are: Kilo, Mega, Giga, Tera, Peta, Exa */
+	static const char prefixes[] = " KMGTPE";
+
+	int		i, r;
+	u_int64_t	max;
+
+	if (len > 0)
+		buf[0] = '\0';
+	if (len < 6)
+		return (-1);		/* not enough room for `xx yB\0' */
+
+	for (max = 1, i = 0; i < len - 4; i++)
+		max *= 10;
+	for (i = 0; bytes >= max && i < sizeof(prefixes); i++)
+		bytes /= 1024;
+
+	r = snprintf(buf, len, "%qd", (long long)bytes);
+	if (i > 0)
+		r += snprintf(buf + r, len - r, " %cB", prefixes[i]);
+
+	return (r);
+}