1/*	$NetBSD: strpct.c,v 1.2 1998/05/08 18:43:54 fair Exp $	*/
2
3/*-
4 * Copyright (c) 1998 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Erik E. Fair
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 *    must display the following acknowledgement:
20 *        This product includes software developed by the NetBSD
21 *        Foundation, Inc. and its contributors.
22 * 4. Neither the name of The NetBSD Foundation nor the names of its
23 *    contributors may be used to endorse or promote products derived
24 *    from this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36 * POSSIBILITY OF SUCH DAMAGE.
37 */
38
39/*
40 * Calculate a percentage without resorting to floating point
41 * and return a pointer to a string
42 *
43 * "digits" is the number of digits past the decimal place you want
44 * (zero being the straight percentage with no decimals)
45 *
46 * Erik E. Fair <fair@clock.org>, May 8, 1997
47 */
48
49#include <sys/types.h>
50#include <machine/limits.h>
51
52#include <stdio.h>
53
54char * strpct __P((u_long, u_long, u_int));
55
56char *
57strpct(numerator, denominator, digits)
58	u_long  numerator, denominator;
59	u_int   digits;
60{
61        int i;
62        u_long result, factor;
63        static char     percent[32];
64
65        /* I should check for digit overflow here, too XXX */
66	factor = 100L;
67        for(i = 0; i < digits; i++) {
68                factor *= 10;
69        }
70
71        /* watch out for overflow! */
72        if (numerator < (ULONG_MAX / factor)) {
73                numerator *= factor;
74        } else {
75                /* toss some of the bits of lesser significance */
76                denominator /= factor;
77        }
78
79        if (denominator == 0L)
80                denominator = 1L;
81
82        result = numerator / denominator;
83
84        if (digits == 0) {
85                (void) snprintf(percent, sizeof(percent), "%lu%%", result);
86        } else {
87                char    fmt[32];
88
89                /* indirection to produce the right output format */
90                (void) snprintf(fmt, sizeof(fmt), "%%lu.%%0%ulu%%%%", digits);
91
92                factor /= 100L;         /* undo initialization */
93
94                (void) snprintf(percent, sizeof(percent),
95                        fmt, result / factor, result % factor);
96        }
97
98        return(percent);
99}
100