1/*
2 * percent.c		- Take percentage of a number
3 *
4 * Copyright (C) 2006  Theodore Ts'o <tytso@mit.edu>
5 *
6 * %Begin-Header%
7 * This file may be redistributed under the terms of the GNU Library
8 * General Public License, version 2.
9 * %End-Header%
10 */
11
12#include "e2p.h"
13
14#include <stdlib.h>
15
16/*
17 * We work really hard to calculate this accurately, while avoiding
18 * an overflow.  "Is there a hyphen in anal-retentive?"  :-)
19 */
20unsigned int e2p_percent(int percent, unsigned int base)
21{
22	unsigned int mask = ~((1 << (sizeof(unsigned int) - 1) * 8) - 1);
23
24	if (!percent)
25		return 0;
26	if (100 % percent == 0)
27		return base / (100 / percent);
28	if (mask & base)
29		return (base / 100) * percent;
30	return base * percent / 100;
31}
32
33#ifdef DEBUG
34#include <unistd.h>
35#include <stdio.h>
36
37main(int argc, char **argv)
38{
39	unsigned int base;
40	int percent;
41	char *p;
42	int log_block_size = 0;
43
44	if (argc != 3) {
45		fprintf(stderr, "Usage: %s percent base\n", argv[0]);
46		exit(1);
47	}
48
49	percent = strtoul(argv[1], &p, 0);
50	if (p[0] && p[1]) {
51		fprintf(stderr, "Bad percent: %s\n", argv[1]);
52		exit(1);
53	}
54
55	base = strtoul(argv[2], &p, 0);
56	if (p[0] && p[1]) {
57		fprintf(stderr, "Bad base: %s\n", argv[2]);
58		exit(1);
59	}
60
61	printf("%d percent of %u is %u.\n", percent, base,
62	       e2p_percent(percent, base));
63
64	exit(0);
65}
66#endif
67