1 /* $NetBSD: factor.c,v 1.5 1995/03/23 08:28:07 cgd Exp $ */ 2 3 /* 4 * Copyright (c) 1989, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Landon Curt Noll. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #ifndef lint 40 static char copyright[] = 41 "@(#) Copyright (c) 1989, 1993\n\ 42 The Regents of the University of California. All rights reserved.\n"; 43 #endif /* not lint */ 44 45 #ifndef lint 46 #if 0 47 static char sccsid[] = "@(#)factor.c 8.3 (Berkeley) 3/30/94"; 48 #else 49 static char rcsid[] = "$NetBSD: factor.c,v 1.5 1995/03/23 08:28:07 cgd Exp $"; 50 #endif 51 #endif /* not lint */ 52 53 /* 54 * factor - factor a number into primes 55 * 56 * By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo 57 * 58 * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\ 59 * 60 * usage: 61 * factor [number] ... 62 * 63 * The form of the output is: 64 * 65 * number: factor1 factor1 factor2 factor3 factor3 factor3 ... 66 * 67 * where factor1 < factor2 < factor3 < ... 68 * 69 * If no args are given, the list of numbers are read from stdin. 70 */ 71 72 #include <err.h> 73 #include <ctype.h> 74 #include <errno.h> 75 #include <limits.h> 76 #include <stdio.h> 77 #include <stdlib.h> 78 79 #include "primes.h" 80 81 /* 82 * prime[i] is the (i-1)th prime. 83 * 84 * We are able to sieve 2^32-1 because this byte table yields all primes 85 * up to 65537 and 65537^2 > 2^32-1. 86 */ 87 extern ubig prime[]; 88 extern ubig *pr_limit; /* largest prime in the prime array */ 89 90 void pr_fact __P((ubig)); /* print factors of a value */ 91 void usage __P((void)); 92 93 int 94 main(argc, argv) 95 int argc; 96 char *argv[]; 97 { 98 ubig val; 99 int ch; 100 char *p, buf[100]; /* > max number of digits. */ 101 102 while ((ch = getopt(argc, argv, "")) != EOF) 103 switch (ch) { 104 case '?': 105 default: 106 usage(); 107 } 108 argc -= optind; 109 argv += optind; 110 111 /* No args supplied, read numbers from stdin. */ 112 if (argc == 0) 113 for (;;) { 114 if (fgets(buf, sizeof(buf), stdin) == NULL) { 115 if (ferror(stdin)) 116 err(1, "stdin"); 117 exit (0); 118 } 119 for (p = buf; isblank(*p); ++p); 120 if (*p == '\n' || *p == '\0') 121 continue; 122 if (*p == '-') 123 errx(1, "negative numbers aren't permitted."); 124 errno = 0; 125 val = strtoul(buf, &p, 10); 126 if (errno) 127 err(1, "%s", buf); 128 if (*p != '\n') 129 errx(1, "%s: illegal numeric format.", buf); 130 pr_fact(val); 131 } 132 /* Factor the arguments. */ 133 else 134 for (; *argv != NULL; ++argv) { 135 if (argv[0][0] == '-') 136 errx(1, "negative numbers aren't permitted."); 137 errno = 0; 138 val = strtoul(argv[0], &p, 10); 139 if (errno) 140 err(1, "%s", argv[0]); 141 if (*p != '\0') 142 errx(1, "%s: illegal numeric format.", argv[0]); 143 pr_fact(val); 144 } 145 exit(0); 146 } 147 148 /* 149 * pr_fact - print the factors of a number 150 * 151 * If the number is 0 or 1, then print the number and return. 152 * If the number is < 0, print -1, negate the number and continue 153 * processing. 154 * 155 * Print the factors of the number, from the lowest to the highest. 156 * A factor will be printed numtiple times if it divides the value 157 * multiple times. 158 * 159 * Factors are printed with leading tabs. 160 */ 161 void 162 pr_fact(val) 163 ubig val; /* Factor this value. */ 164 { 165 ubig *fact; /* The factor found. */ 166 167 /* Firewall - catch 0 and 1. */ 168 if (val == 0) /* Historical practice; 0 just exits. */ 169 exit(0); 170 if (val == 1) { 171 (void)printf("1: 1\n"); 172 return; 173 } 174 175 /* Factor value. */ 176 (void)printf("%lu:", val); 177 for (fact = &prime[0]; val > 1; ++fact) { 178 /* Look for the smallest factor. */ 179 do { 180 if (val % (long)*fact == 0) 181 break; 182 } while (++fact <= pr_limit); 183 184 /* Watch for primes larger than the table. */ 185 if (fact > pr_limit) { 186 (void)printf(" %lu", val); 187 break; 188 } 189 190 /* Divide factor out until none are left. */ 191 do { 192 (void)printf(" %lu", *fact); 193 val /= (long)*fact; 194 } while ((val % (long)*fact) == 0); 195 196 /* Let the user know we're doing something. */ 197 (void)fflush(stdout); 198 } 199 (void)putchar('\n'); 200 } 201 202 void 203 usage() 204 { 205 (void)fprintf(stderr, "usage: factor [value ...]\n"); 206 exit (0); 207 } 208