1 /* $NetBSD: factor.c,v 1.6 1997/01/07 12:05:10 tls 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 8.4 (Berkeley) 5/4/95"; 48 #else 49 static char rcsid[] = "$NetBSD: factor.c,v 1.6 1997/01/07 12:05:10 tls 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 #include <unistd.h> 79 80 #include "primes.h" 81 82 /* 83 * prime[i] is the (i-1)th prime. 84 * 85 * We are able to sieve 2^32-1 because this byte table yields all primes 86 * up to 65537 and 65537^2 > 2^32-1. 87 */ 88 extern ubig prime[]; 89 extern ubig *pr_limit; /* largest prime in the prime array */ 90 91 void pr_fact __P((ubig)); /* print factors of a value */ 92 void usage __P((void)); 93 94 int 95 main(argc, argv) 96 int argc; 97 char *argv[]; 98 { 99 ubig val; 100 int ch; 101 char *p, buf[100]; /* > max number of digits. */ 102 103 while ((ch = getopt(argc, argv, "")) != EOF) 104 switch (ch) { 105 case '?': 106 default: 107 usage(); 108 } 109 argc -= optind; 110 argv += optind; 111 112 /* No args supplied, read numbers from stdin. */ 113 if (argc == 0) 114 for (;;) { 115 if (fgets(buf, sizeof(buf), stdin) == NULL) { 116 if (ferror(stdin)) 117 err(1, "stdin"); 118 exit (0); 119 } 120 for (p = buf; isblank(*p); ++p); 121 if (*p == '\n' || *p == '\0') 122 continue; 123 if (*p == '-') 124 errx(1, "negative numbers aren't permitted."); 125 errno = 0; 126 val = strtoul(buf, &p, 10); 127 if (errno) 128 err(1, "%s", buf); 129 if (*p != '\n') 130 errx(1, "%s: illegal numeric format.", buf); 131 pr_fact(val); 132 } 133 /* Factor the arguments. */ 134 else 135 for (; *argv != NULL; ++argv) { 136 if (argv[0][0] == '-') 137 errx(1, "negative numbers aren't permitted."); 138 errno = 0; 139 val = strtoul(argv[0], &p, 10); 140 if (errno) 141 err(1, "%s", argv[0]); 142 if (*p != '\0') 143 errx(1, "%s: illegal numeric format.", argv[0]); 144 pr_fact(val); 145 } 146 exit(0); 147 } 148 149 /* 150 * pr_fact - print the factors of a number 151 * 152 * If the number is 0 or 1, then print the number and return. 153 * If the number is < 0, print -1, negate the number and continue 154 * processing. 155 * 156 * Print the factors of the number, from the lowest to the highest. 157 * A factor will be printed numtiple times if it divides the value 158 * multiple times. 159 * 160 * Factors are printed with leading tabs. 161 */ 162 void 163 pr_fact(val) 164 ubig val; /* Factor this value. */ 165 { 166 ubig *fact; /* The factor found. */ 167 168 /* Firewall - catch 0 and 1. */ 169 if (val == 0) /* Historical practice; 0 just exits. */ 170 exit(0); 171 if (val == 1) { 172 (void)printf("1: 1\n"); 173 return; 174 } 175 176 /* Factor value. */ 177 (void)printf("%lu:", val); 178 for (fact = &prime[0]; val > 1; ++fact) { 179 /* Look for the smallest factor. */ 180 do { 181 if (val % (long)*fact == 0) 182 break; 183 } while (++fact <= pr_limit); 184 185 /* Watch for primes larger than the table. */ 186 if (fact > pr_limit) { 187 (void)printf(" %lu", val); 188 break; 189 } 190 191 /* Divide factor out until none are left. */ 192 do { 193 (void)printf(" %lu", *fact); 194 val /= (long)*fact; 195 } while ((val % (long)*fact) == 0); 196 197 /* Let the user know we're doing something. */ 198 (void)fflush(stdout); 199 } 200 (void)putchar('\n'); 201 } 202 203 void 204 usage() 205 { 206 (void)fprintf(stderr, "usage: factor [value ...]\n"); 207 exit (0); 208 } 209