bin/csh/strpct.c

   1 /* $NetBSD: strpct.c,v 1.7 2008/04/28 20:22:51 martin 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 1.7 2008/04/28 20:22:51 martin Exp $");
  44
  45 #include <sys/types.h>
  46
  47 #include <limits.h>
  48 #include <stdio.h>
  49
  50 char *strpct(u_long, u_long, u_int);
  51
  52 char *
  53 strpct(u_long numerator, u_long denominator, u_int digits)
  54 {
  55         static char percent[32];
  56         u_long factor, result;
  57         u_int u;
  58
  59         /* I should check for digit overflow here, too XXX */
  60         factor = 100L;
  61         for (u = 0; u < digits; u++) {
  62                 factor *= 10;
  63         }
  64
  65         /* watch out for overflow! */
  66         if (numerator < (ULONG_MAX / factor))
  67                 numerator *= factor;
  68         else {
  69                 /* toss some of the bits of lesser significance */
  70                 denominator /= factor;
  71         }
  72
  73         if (denominator == 0L)
  74                 denominator = 1L;
  75
  76         result = numerator / denominator;
  77
  78         if (digits == 0)
  79                 (void)snprintf(percent, sizeof(percent), "%lu%%", result);
  80         else {
  81                 char    fmt[32];
  82
  83                 /* indirection to produce the right output format */
  84                 (void)snprintf(fmt, sizeof(fmt), "%%lu.%%0%ulu%%%%", digits);
  85
  86                 factor /= 100L;         /* undo initialization */
  87
  88                 (void)snprintf(percent, sizeof(percent), fmt, result / factor,
  89                     result % factor);
  90         }
  91
  92         return (percent);
  93 }