usr/src/games/factor/factor.c

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

#ifndef lint
static char sccsid[] = "@(#)factor.c    4.4 (Berkeley) 6/1/90";
#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 <stdio.h>
#include <ctype.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 */

#define MAX_LINE 255    /* max line allowed on stdin */

void pr_fact();         /* print factors of a value */
long small_fact();      /* find smallest factor of a value */
char *read_num_buf();   /* read a number buffer */
char *program;          /* name of this program */

main(argc, argv)
        int argc;       /* arg count */
        char *argv[];   /* the args */
{
        int arg;        /* which arg to factor */
        long val;       /* the value to factor */
        char buf[MAX_LINE+1];   /* input buffer */

        /* parse args */
        program = argv[0];
        if (argc >= 2) {

                /* factor each arg */
                for (arg=1; arg < argc; ++arg) {

                        /* process the buffer */
                        if (read_num_buf(NULL, argv[arg]) == NULL) {
                                fprintf(stderr, "%s: ouch\n", program);
                                exit(1);
                        }

                        /* factor the argument */
                        if (sscanf(argv[arg], "%ld", &val) == 1) {
                                pr_fact(val);
                        } else {
                                fprintf(stderr, "%s: ouch\n", program);
                                exit(1);
                        }
                }

        /* no args supplied, read numbers from stdin */
        } else {
                /*
                 * read asciii numbers from input
                 */
                while (read_num_buf(stdin, buf) != NULL) {

                        /* factor the argument */
                        if (sscanf(buf, "%ld", &val) == 1) {
                                pr_fact(val);
                        }
                }
        }
        exit(0);
}

/*
 * read_num_buf - read a number buffer from a stream
 *
 * Read a number on a line of the form:
 *
 *      ^[ \t]*\([+-]?[0-9][0-9]\)*.*$
 *
 * where ? is a 1-or-0 operator and the number is within \( \).
 *
 * If does not match the above pattern, it is ignored and a new
 * line is read.  If the number is too large or small, we will
 * print ouch and read a new line.
 *
 * We have to be very careful on how we check the magnitude of the
 * input.  We can not use numeric checks because of the need to
 * check values against maximum numeric values.
 *
 * This routine will return a line containing a ascii number between
 * NEG_SEMIBIG and SEMIBIG, or it will return NULL.
 *
 * If the stream is NULL then buf will be processed as if were
 * a single line stream.
 *
 * returns:
 *      char *  pointer to leading digit, + or -
 *      NULL    EOF or error
 */
char *
read_num_buf(input, buf)
        FILE *input;            /* input stream or NULL */
        char *buf;              /* input buffer */
{
        static char limit[MAX_LINE+1];  /* ascii value of SEMIBIG */
        static int limit_len;           /* digit count of limit */
        static char neg_limit[MAX_LINE+1];      /* value of NEG_SEMIBIG */
        static int neg_limit_len;               /* digit count of neg_limit */
        int len;                        /* digits in input (excluding +/-) */
        char *s;        /* line start marker */
        char *d;        /* first digit, skip +/- */
        char *p;        /* scan pointer */
        char *z;        /* zero scan pointer */

        /* form the ascii value of SEMIBIG if needed */
        if (!isascii(limit[0]) || !isdigit(limit[0])) {
                sprintf(limit, "%ld", SEMIBIG);
                limit_len = strlen(limit);
                sprintf(neg_limit, "%ld", NEG_SEMIBIG);
                neg_limit_len = strlen(neg_limit)-1;    /* exclude - */
        }

        /*
         * the search for a good line
         */
        if (input != NULL && fgets(buf, MAX_LINE, input) == NULL) {
                /* error or EOF */
                return NULL;
        }
        do {

                /* ignore leading whitespace */
                for (s=buf; *s && s < buf+MAX_LINE; ++s) {
                        if (!isascii(*s) || !isspace(*s)) {
                                break;
                        }
                }

                /* skip over any leading + or - */
                if (*s == '+' || *s == '-') {
                        d = s+1;
                } else {
                        d = s;
                }

                /* note leading zeros */
                for (z=d; *z && z < buf+MAX_LINE; ++z) {
                        if (*z != '0') {
                                break;
                        }
                }

                /* scan for the first non-digit */
                for (p=d; *p && p < buf+MAX_LINE; ++p) {
                        if (!isascii(*p) || !isdigit(*p)) {
                                break;
                        }
                }

                /* ignore empty lines */
                if (p == d) {
                        continue;
                }
                *p = '\0';

                /* object if too many digits */
                len = strlen(z);
                len = (len<=0) ? 1 : len;
                if (*s == '-') {
                        /* accept if digit count is below limit */
                        if (len < neg_limit_len) {
                                /* we have good input */
                                return s;

                        /* reject very large numbers */
                        } else if (len > neg_limit_len) {
                                fprintf(stderr, "%s: ouch\n", program);
                                exit(1);

                        /* carefully check against near limit numbers */
                        } else if (strcmp(z, neg_limit+1) > 0) {
                                fprintf(stderr, "%s: ouch\n", program);
                                exit(1);
                        }
                        /* number is near limit, but is under it */
                        return s;

                } else {
                        /* accept if digit count is below limit */
                        if (len < limit_len) {
                                /* we have good input */
                                return s;

                        /* reject very large numbers */
                        } else if (len > limit_len) {
                                fprintf(stderr, "%s: ouch\n", program);
                                exit(1);

                        /* carefully check against near limit numbers */
                        } else if (strcmp(z, limit) > 0) {
                                fprintf(stderr, "%s: ouch\n", program);
                                exit(1);
                        }
                        /* number is near limit, but is under it */
                        return s;
                }
        } while (input != NULL && fgets(buf, MAX_LINE, input) != NULL);

        /* error or EOF */
        return NULL;
}


/*
 * 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)
        long val;       /* factor this value */
{
        ubig *fact;     /* the factor found */

        /* firewall - catch 0 and 1 */
        switch (val) {
        case -2147483648:
                /* avoid negation problems */
                puts("-2147483648: -1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2\n");
                return;
        case -1:
                puts("-1: -1\n");
                return;
        case 0:
                exit(0);
        case 1:
                puts("1: 1\n");
                return;
        default:
                if (val < 0) {
                        val = -val;
                        printf("%ld: -1", val);
                } else {
                        printf("%ld:", val);
                }
                fflush(stdout);
                break;
        }

        /*
         * factor value
         */
        fact = &prime[0];
        while (val > 1) {

                /* 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) {
                        printf(" %ld\n", val);
                        return;
                }

                /* divide factor out until none are left */
                do {
                        printf(" %ld", *fact);
                        val /= (long)*fact;
                } while ((val % (long)*fact) == 0);
                fflush(stdout);
                ++fact;
        }
        putchar('\n');
        return;
}