File: factor.c

package info (click to toggle)
bsdgames 2.5-4
  • links: PTS
  • area: main
  • in suites: slink
  • size: 8,412 kB
  • ctags: 4,665
  • sloc: ansic: 59,763; sh: 643; yacc: 327; lex: 79; makefile: 53; sed: 13; csh: 5
file content (212 lines) | stat: -rw-r--r-- 5,846 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
/*	$NetBSD: factor.c,v 1.8 1998/09/13 15:27:27 hubertf Exp $	*/

/*
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Landon Curt Noll.
 *
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */

#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\
	The Regents of the University of California.  All rights reserved.\n");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)factor.c	8.4 (Berkeley) 5/4/95";
#else
__RCSID("$NetBSD: factor.c,v 1.8 1998/09/13 15:27:27 hubertf Exp $");
#endif
#endif /* not lint */

/*
 * factor - factor a number into primes
 *
 * By: Landon Curt Noll   chongo@toad.com,   ...!{sun,tolsoft}!hoptoad!chongo
 *
 *   chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\
 *
 * usage:
 *	factor [number] ...
 *
 * The form of the output is:
 *
 *	number: factor1 factor1 factor2 factor3 factor3 factor3 ...
 *
 * where factor1 < factor2 < factor3 < ...
 *
 * If no args are given, the list of numbers are read from stdin.
 */

#include <err.h>
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include "primes.h"

/*
 * prime[i] is the (i-1)th prime.
 *
 * We are able to sieve 2^32-1 because this byte table yields all primes 
 * up to 65537 and 65537^2 > 2^32-1.
 */
extern const ubig prime[];
extern const ubig *pr_limit;		/* largest prime in the prime array */

int	main __P((int, char *[]));
void	pr_fact __P((ubig));	/* print factors of a value */
void	usage __P((void)) __attribute__((__noreturn__));

int
main(argc, argv)
	int argc;
	char *argv[];
{
	ubig val;
	int ch;
	char *p, buf[100];		/* > max number of digits. */

	/* Revoke setgid privileges */
	setregid(getgid(), getgid());

	while ((ch = getopt(argc, argv, "")) != -1)
		switch (ch) {
		case '?':
		default:
			usage();
		}
	argc -= optind;
	argv += optind;

	/* No args supplied, read numbers from stdin. */
	if (argc == 0)
		for (;;) {
			if (fgets(buf, sizeof(buf), stdin) == NULL) {
				if (ferror(stdin))
					err(1, "stdin");
				exit (0);
			}
			for (p = buf; isblank(*p); ++p);
			if (*p == '\n' || *p == '\0')
				continue;
			if (*p == '-')
				errx(1, "negative numbers aren't permitted.");
			errno = 0;
			val = strtoul(buf, &p, 10);
			if (errno)
				err(1, "%s", buf);
			if (*p != '\n')
				errx(1, "%s: illegal numeric format.", buf);
			pr_fact(val);
		}
	/* Factor the arguments. */
	else
		for (; *argv != NULL; ++argv) {
			if (argv[0][0] == '-')
				errx(1, "negative numbers aren't permitted.");
			errno = 0;
			val = strtoul(argv[0], &p, 10);
			if (errno)
				err(1, "%s", argv[0]);
			if (*p != '\0')
				errx(1, "%s: illegal numeric format.", argv[0]);
			pr_fact(val);
		}
	exit(0);
}

/*
 * pr_fact - print the factors of a number
 *
 * If the number is 0 or 1, then print the number and return.
 * If the number is < 0, print -1, negate the number and continue
 * processing.
 *
 * Print the factors of the number, from the lowest to the highest.
 * A factor will be printed numtiple times if it divides the value
 * multiple times.
 *
 * Factors are printed with leading tabs.
 */
void
pr_fact(val)
	ubig val;		/* Factor this value. */
{
	const ubig *fact;		/* The factor found. */

	/* Firewall - catch 0 and 1. */
	if (val == 0)		/* Historical practice; 0 just exits. */
		exit(0);
	if (val == 1) {
		(void)printf("1: 1\n");
		return;
	}

	/* Factor value. */
	(void)printf("%lu:", val);
	for (fact = &prime[0]; val > 1; ++fact) {
		/* Look for the smallest factor. */
		do {
			if (val % (long)*fact == 0)
				break;
		} while (++fact <= pr_limit);

		/* Watch for primes larger than the table. */
		if (fact > pr_limit) {
			(void)printf(" %lu", val);
			break;
		}

		/* Divide factor out until none are left. */
		do {
			(void)printf(" %lu", *fact);
			val /= (long)*fact;
		} while ((val % (long)*fact) == 0);

		/* Let the user know we're doing something. */
		(void)fflush(stdout);
	}
	(void)putchar('\n');
}

void
usage()
{
	(void)fprintf(stderr, "usage: factor [value ...]\n");
	exit (0);
}