1 /* $NetBSD: strpct.c,v 1.2 2011/09/02 10:13:44 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 1.2 2011/09/02 10:13:44 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 * 53 strpct(char *buf, size_t bufsiz, uintmax_t numerator, uintmax_t denominator, 54 size_t digits) 55 { 56 uintmax_t factor, result; 57 size_t u; 58 59 factor = 100; 60 for (u = 0; u < digits; u++) { 61 /* watch out for overflow! */ 62 if (factor < (UINTMAX_MAX / 10)) 63 factor *= 10; 64 else 65 break; 66 } 67 68 /* watch out for overflow! */ 69 if (numerator < (UINTMAX_MAX / factor)) 70 numerator *= factor; 71 else { 72 /* toss some of the bits of lesser significance */ 73 denominator /= factor; 74 } 75 76 if (denominator == 0) 77 denominator = 1; 78 79 result = numerator / denominator; 80 81 if (digits == 0) 82 (void)snprintf(buf, bufsiz, "%ju", result); 83 else { 84 factor /= 100; /* undo initialization */ 85 86 (void)snprintf(buf, bufsiz, "%ju%s%0*ju", 87 result / factor, localeconv()->decimal_point, (int)u, 88 result % factor); 89 } 90 91 return buf; 92 } 93