usr/src/games/factor/factor.c

/*
 * 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.
 */

#ifndef lint
static char copyright[] =
"@(#) Copyright (c) 1989, 1993\n\
        The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)factor.c    8.3 (Berkeley) 3/30/94";
#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 "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 ubig prime[];
extern ubig *pr_limit;          /* largest prime in the prime array */

void    pr_fact __P((ubig));    /* print factors of a value */
void    usage __P((void));

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

        while ((ch = getopt(argc, argv, "")) != EOF)
                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. */
{
        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);
}