/*      $NetBSD: factor.c,v 1.38 2020/10/12 13:54:51 christos 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. 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
#include <sys/cdefs.h>
#ifdef __COPYRIGHT
__COPYRIGHT("@(#) Copyright (c) 1989, 1993\
        The Regents of the University of California.  All rights reserved.");
#endif
#ifdef __SCCSID
__SCCSID("@(#)factor.c  8.4 (Berkeley) 5/4/95");
#endif
#ifdef __RCSID
__RCSID("$NetBSD: factor.c,v 1.38 2020/10/12 13:54:51 christos Exp $");
#endif
#ifdef __FBSDID
__FBSDID("$FreeBSD: head/usr.bin/factor/factor.c 356666 2020-01-12 20:25:11Z gad $");
#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 [-hx] [number] ...
 *
 * The form of the output is:
 *
 *      number: factor1 factor1 factor2 factor3 factor3 factor3 ...
 *
 * where factor1 <= factor2 <= factor3 <= ...
 *
 * If the -h flag is specified, the output is in "human-readable" format.
 * Duplicate factors are printed in the form of x^n.
 *
 * If the -x flag is specified numbers are printed in hex.
 *
 * If no number args are given, the list of numbers are read from stdin.
 */

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

#include "primes.h"

#ifdef HAVE_OPENSSL

#include <openssl/bn.h>

#define PRIME_CHECKS    5

/* print factors for big numbers */
static void     pollard_pminus1(BIGNUM *, int, int);

#else

typedef long    BIGNUM;
typedef u_long  BN_ULONG;

#define BN_CTX                  int
#define BN_CTX_new()            NULL
#define BN_new()                calloc(sizeof(BIGNUM), 1)
#define BN_free(a)              free(a)

#define BN_copy(a, b)           *(a) = *(b)
#define BN_cmp(a, b)            (*(a) - *(b))
#define BN_is_zero(v)           (*(v) == 0)
#define BN_is_one(v)            (*(v) == 1)
#define BN_mod_word(a, b)       (*(a) % (b))

static BIGNUM  *BN_dup(const BIGNUM *);
static int      BN_dec2bn(BIGNUM **, const char *);
static int      BN_hex2bn(BIGNUM **, const char *);
static BN_ULONG BN_div_word(BIGNUM *, BN_ULONG);
static void     BN_print_fp(FILE *, const BIGNUM *);

#endif

static void     BN_print_dec_fp(FILE *, const BIGNUM *);
static void     convert_str2bn(BIGNUM **, char *);
static void     pr_fact(BIGNUM *, int, int);    /* print factors of a value */
static void     pr_print(BIGNUM *, int, int);   /* print a prime */
static void     usage(void) __dead;

static BN_CTX   *ctx;                   /* just use a global context */

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

        hflag = xflag = 0;
        ctx = BN_CTX_new();
        val = BN_new();
        if (val == NULL)
                errx(1, "can't initialise bignum");

        while ((ch = getopt(argc, argv, "hx")) != -1)
                switch (ch) {
                case 'h':
                        hflag++;
                        break;
                case 'x':
                        xflag++;
                        break;
                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((unsigned char)*p); ++p);
                        if (*p == '\n' || *p == '\0')
                                continue;
                        convert_str2bn(&val, p);
                        pr_fact(val, hflag, xflag);
                }
        /* Factor the arguments. */
        else
                for (p = *argv; p != NULL; p = *++argv) {
                        convert_str2bn(&val, p);
                        pr_fact(val, hflag, xflag);
                }
        exit(0);
}

static void
pr_exp(int i, int xflag)
{
        printf(xflag && i > 9 ? "^0x%x" : "^%d", i);
}

static void
pr_uint64(uint64_t i, int xflag)
{
        printf(xflag ? " 0x%" PRIx64 : " %" PRIu64, i);
}

/*
 * pr_fact - print the factors of a number
 *
 * Print the factors of the number, from the lowest to the highest.
 * A factor will be printed multiple times if it divides the value
 * multiple times.
 *
 * If hflag is specified, duplicate factors are printed in "human-
 * readable" form of x^n.
 *
 * If the xflag is specified, numbers will be printed in hex.
 *
 * Factors are printed with leading tabs.
 */
static void
pr_fact(BIGNUM *val, int hflag, int xflag)
{
        int i;
        const uint64_t *fact;   /* The factor found. */

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

        /* Factor value. */

        if (xflag) {
                fputs("0x", stdout);
                BN_print_fp(stdout, val);
        } else
                BN_print_dec_fp(stdout, val);
        putchar(':');
        fflush(stdout);
        for (fact = &prime[0]; !BN_is_one(val); ++fact) {
                /* Look for the smallest factor. */
                do {
                        if (BN_mod_word(val, (BN_ULONG)*fact) == 0)
                                break;
                } while (++fact <= pr_limit);

                /* Watch for primes larger than the table. */
                if (fact > pr_limit) {
#ifdef HAVE_OPENSSL
                        BIGNUM *bnfact;

                        bnfact = BN_new();
                        BN_set_word(bnfact, *(fact - 1));
                        if (!BN_sqr(bnfact, bnfact, ctx))
                                errx(1, "error in BN_sqr()");
                        if (BN_cmp(bnfact, val) > 0 ||
                            BN_is_prime_ex(val, PRIME_CHECKS, NULL, NULL) == 1)
                                pr_print(val, hflag, xflag);
                        else
                                pollard_pminus1(val, hflag, xflag);
#else
                        pr_print(val, hflag, xflag);
#endif
                        pr_print(NULL, hflag, xflag);
                        break;
                }

                /* Divide factor out until none are left. */
                i = 0;
                do {
                        i++;
                        if (!hflag)
                                pr_uint64(*fact, xflag);
                        BN_div_word(val, (BN_ULONG)*fact);
                } while (BN_mod_word(val, (BN_ULONG)*fact) == 0);

                if (hflag) {
                        pr_uint64(*fact, xflag);
                        if (i > 1)
                                pr_exp(i, xflag);
                }

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

static void
pr_print(BIGNUM *val, int hflag, int xflag)
{
        static BIGNUM *sval;
        static int ex = 1;
        BIGNUM *pval;

        if (hflag) {
                if (sval == NULL) {
                        sval = BN_dup(val);
                        return;
                }

                if (val != NULL && BN_cmp(val, sval) == 0) {
                        ex++;
                        return;
                }
                pval = sval;
        } else if (val == NULL) {
                return;
        } else {
                pval = val;
        }

        if (xflag) {
                fputs(" 0x", stdout);
                BN_print_fp(stdout, pval);
        } else {
                putchar(' ');
                BN_print_dec_fp(stdout, pval);
        }

        if (hflag) {
                if (ex > 1)
                        pr_exp(ex, xflag);

                if (val != NULL) {
                        BN_copy(sval, val);
                } else {
                        BN_free(sval);
                        sval = NULL;
                }
                ex = 1;
        }
}

static void
usage(void)
{
        fprintf(stderr, "Usage: %s [-hx] [value ...]\n", getprogname());
        exit(1);
}

#ifdef HAVE_OPENSSL

/* pollard p-1, algorithm from Jim Gillogly, May 2000 */
static void
pollard_pminus1(BIGNUM *val, int hflag, int xflag)
{
        BIGNUM *base, *rbase, *num, *i, *x;

        base = BN_new();
        rbase = BN_new();
        num = BN_new();
        i = BN_new();
        x = BN_new();

        BN_set_word(rbase, 1);
newbase:
        if (!BN_add_word(rbase, 1))
                errx(1, "error in BN_add_word()");
        BN_set_word(i, 2);
        BN_copy(base, rbase);

        for (;;) {
                BN_mod_exp(base, base, i, val, ctx);
                if (BN_is_one(base))
                        goto newbase;

                BN_copy(x, base);
                BN_sub_word(x, 1);
                if (!BN_gcd(x, x, val, ctx))
                        errx(1, "error in BN_gcd()");

                if (!BN_is_one(x)) {
                        if (BN_is_prime_ex(x, PRIME_CHECKS, NULL, NULL) == 1)
                                pr_print(x, hflag, xflag);
                        else
                                pollard_pminus1(x, hflag, xflag);
                        fflush(stdout);

                        BN_div(num, NULL, val, x, ctx);
                        if (BN_is_one(num))
                                return;
                        if (BN_is_prime_ex(num, PRIME_CHECKS, NULL,
                            NULL) == 1) {
                                pr_print(num, hflag, xflag);
                                fflush(stdout);
                                return;
                        }
                        BN_copy(val, num);
                }
                if (!BN_add_word(i, 1))
                        errx(1, "error in BN_add_word()");
        }
}

/*
 * Sigh..  No _decimal_ output to file functions in BN.
 */
static void
BN_print_dec_fp(FILE *fp, const BIGNUM *num)
{
        char *buf;

        buf = BN_bn2dec(num);
        if (buf == NULL)
                return; /* XXX do anything here? */
        fprintf(fp, "%s", buf);
        free(buf);
}

#else

static void
BN_print_fp(FILE *fp, const BIGNUM *num)
{
        fprintf(fp, "%lx", (unsigned long)*num);
}

static void
BN_print_dec_fp(FILE *fp, const BIGNUM *num)
{
        fprintf(fp, "%lu", (unsigned long)*num);
}

static int
BN_dec2bn(BIGNUM **a, const char *str)
{
        char *p;

        errno = 0;
        **a = strtoul(str, &p, 10);
        return (errno == 0 ? 1 : 0);    /* OpenSSL returns 0 on error! */
}

static int
BN_hex2bn(BIGNUM **a, const char *str)
{
        char *p;

        errno = 0;
        **a = strtoul(str, &p, 16);
        return (errno == 0 ? 1 : 0);    /* OpenSSL returns 0 on error! */
}

static BN_ULONG
BN_div_word(BIGNUM *a, BN_ULONG b)
{
        BN_ULONG mod;

        mod = *a % b;
        *a /= b;
        return mod;
}

static BIGNUM *
BN_dup(const BIGNUM *a)
{
        BIGNUM *b = BN_new();
        BN_copy(b, a);
        return b;
}

#endif

/* Convert string pointed to by *str to a bignum.  */
static void
convert_str2bn(BIGNUM **val, char *p)
{
        int n = 0;

        if (*p == '+') p++;
        if (*p == '-')
                errx(1, "negative numbers aren't permitted.");
        if (*p == '0' && (p[1] == 'x' || p[1] == 'X')) {
                n = BN_hex2bn(val, p + 2);
        } else {
                n = BN_dec2bn(val, p);
        }
        if (n == 0)
                errx(1, "%s: illegal numeric format.", p);
}