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 */
e2p_percent(int percent,unsigned int base)20 unsigned 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
main(int argc,char ** argv)37 main(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