lib/libutil/strpct.c

   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 *
  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 *
  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 }