1 /* $NetBSD: strpct.c,v 1.3 2012/01/07 18:40:56 christos 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 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 /*
33 * Calculate a percentage without resorting to floating point
34 * and return a pointer to a string
35 *
36 * "digits" is the number of digits past the decimal place you want
37 * (zero being the straight percentage with no decimals)
38 *
39 * Erik E. Fair <fair@clock.org>, May 8, 1997
40 */
41
42 #include <sys/cdefs.h>
43 __RCSID("$NetBSD: strpct.c,v 1.3 2012/01/07 18:40:56 christos Exp $");
44
45 #include <stdint.h>
46 #include <locale.h>
47 #include <limits.h>
48 #include <stdio.h>
49 #include <errno.h>
50 #include <util.h>
51
52 char *
strspct(char * buf,size_t bufsiz,intmax_t numerator,intmax_t denominator,size_t digits)53 strspct(char *buf, size_t bufsiz, intmax_t numerator, intmax_t denominator,
54 size_t digits)
55 {
56 int sign;
57
58 switch (bufsiz) {
59 case 1:
60 *buf = '\0';
61 /*FALLTHROUGH*/
62 case 0:
63 return buf;
64 default:
65 break;
66 }
67
68 if (denominator < 0) {
69 denominator = -denominator;
70 sign = 1;
71 } else
72 sign = 0;
73
74 if (numerator < 0) {
75 numerator = -numerator;
76 sign++;
77 }
78
79 sign &= 1;
80 (void)strpct(buf + sign, bufsiz - sign, (uintmax_t)numerator,
81 (uintmax_t)denominator, digits);
82 if (sign)
83 *buf = '-';
84 return buf;
85 }
86
87 char *
strpct(char * buf,size_t bufsiz,uintmax_t numerator,uintmax_t denominator,size_t digits)88 strpct(char *buf, size_t bufsiz, uintmax_t numerator, uintmax_t denominator,
89 size_t digits)
90 {
91 uintmax_t factor, result;
92 size_t u;
93
94 factor = 100;
95 for (u = 0; u < digits; u++) {
96 /* watch out for overflow! */
97 if (factor < (UINTMAX_MAX / 10))
98 factor *= 10;
99 else
100 break;
101 }
102
103 /* watch out for overflow! */
104 if (numerator < (UINTMAX_MAX / factor))
105 numerator *= factor;
106 else {
107 /* toss some of the bits of lesser significance */
108 denominator /= factor;
109 }
110
111 if (denominator == 0)
112 denominator = 1;
113
114 result = numerator / denominator;
115
116 if (digits == 0)
117 (void)snprintf(buf, bufsiz, "%ju", result);
118 else {
119 factor /= 100; /* undo initialization */
120
121 (void)snprintf(buf, bufsiz, "%ju%s%0*ju",
122 result / factor, localeconv()->decimal_point, (int)u,
123 result % factor);
124 }
125
126 return buf;
127 }
128