NetBSD/bin/csh/strpct.c

/* $NetBSD: strpct.c,v 1.8 2009/02/13 00:46:25 abs Exp $ */

/*-
 * Copyright (c) 1998 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Erik E. Fair
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Calculate a percentage without resorting to floating point
 * and return a pointer to a string
 *
 * "digits" is the number of digits past the decimal place you want
 * (zero being the straight percentage with no decimals)
 *
 * Erik E. Fair <fair@clock.org>, May 8, 1997
 */

#include <sys/cdefs.h>
__RCSID("$NetBSD: strpct.c,v 1.8 2009/02/13 00:46:25 abs Exp $");

#include <sys/types.h>

#include <limits.h>
#include <stdio.h>

char *strpct(u_long, u_long, u_int);

char *
strpct(u_long numerator, u_long denominator, u_int digits)
{
	static char percent[32];
	u_long factor, result;
	u_int u;

	/* I should check for digit overflow here, too XXX */
	factor = 100L;
	for (u = 0; u < digits; u++) {
		factor *= 10;
	}

	/* watch out for overflow! */
	if (numerator < (ULONG_MAX / factor))
		numerator *= factor;
	else {
		/* toss some of the bits of lesser significance */
		denominator /= factor;
	}

	if (denominator == 0L)
		denominator = 1L;

	result = numerator / denominator;

	if (digits == 0)
		(void)snprintf(percent, sizeof(percent), "%lu%%", result);
	else {
		char	fmt[32];

		/* indirection to produce the right output format */
		(void)snprintf(fmt, sizeof(fmt), "%%lu.%%0%ulu%%%%", digits);

		factor /= 100L;		/* undo initialization */

		(void)snprintf(percent, sizeof(percent), fmt, result / factor,
		    result % factor);
	}       

	return (percent);
}