convtbl.c revision 164671 
1/*
2 * Copyright (c) 2003, Trent Nelson, <trent@arpa.com>.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote products
14 *    derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * $FreeBSD: head/usr.bin/systat/convtbl.c 164671 2006-11-27 15:26:26Z yar $
29 */
30
31#include <sys/types.h>
32#include <unistd.h>
33#include "convtbl.h"
34
35struct	convtbl convtbl[] = {
36	/* mul, scale, str */
37	[SC_BYTE] =	{ BYTE, BYTES, "bytes" },
38	[SC_KILOBYTE] =	{ BYTE, KILO, "KB" },
39	[SC_MEGABYTE] =	{ BYTE, MEGA, "MB" },
40	[SC_GIGABYTE] =	{ BYTE, GIGA, "GB" },
41
42	[SC_BIT] =	{ BIT, BITS, "b" },
43	[SC_KILOBIT] =	{ BIT, KILO, "Kb" },
44	[SC_MEGABIT] =	{ BIT, MEGA, "Mb" },
45	[SC_GIGABIT] =	{ BIT, GIGA, "Gb" },
46
47	[SC_AUTO] =	{ 0, 0, "" }
48};
49
50
51static
52struct convtbl *
53get_tbl_ptr(const uintmax_t size, const int scale)
54{
55	uintmax_t	 tmp;
56	int		 idx;
57
58	/* If our index is out of range, default to auto-scaling. */
59	idx = scale < SC_AUTO ? scale : SC_AUTO;
60
61	if (idx == SC_AUTO)
62		/*
63		 * Simple but elegant algorithm.  Count how many times
64		 * we can shift our size value right by a factor of ten,
65		 * incrementing an index each time.  We then use the
66		 * index as the array index into the conversion table.
67		 */
68		for (tmp = size, idx = SC_KILOBYTE;
69		     tmp >= MEGA && idx < SC_GIGABYTE;
70		     tmp >>= 10, idx++);
71
72	return (&convtbl[idx]);
73}
74
75double
76convert(const uintmax_t size, const int scale)
77{
78	struct convtbl	*tp;
79
80	tp = get_tbl_ptr(size, scale);
81	return ((double)size * tp->mul / tp->scale);
82
83}
84
85const char *
86get_string(const uintmax_t size, const int scale)
87{
88	struct convtbl	*tp;
89
90	tp = get_tbl_ptr(size, scale);
91	return (tp->str);
92}
93