primes/primes.c

   1 /*      $NetBSD: primes.c,v 1.17 2009/08/12 08:25:27 dholland 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. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #include <sys/cdefs.h>
  36 #ifndef lint
  37 __COPYRIGHT("@(#) Copyright (c) 1989, 1993\
  38  The Regents of the University of California.  All rights reserved.");
  39 #endif /* not lint */
  40
  41 #ifndef lint
  42 #if 0
  43 static char sccsid[] = "@(#)primes.c    8.5 (Berkeley) 5/10/95";
  44 #else
  45 __RCSID("$NetBSD: primes.c,v 1.17 2009/08/12 08:25:27 dholland Exp $");
  46 #endif
  47 #endif /* not lint */
  48
  49 /*
  50  * primes - generate a table of primes between two values
  51  *
  52  * By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo
  53  *
  54  * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\
  55  *
  56  * usage:
  57  *      primes [start [stop]]
  58  *
  59  *      Print primes >= start and < stop.  If stop is omitted,
  60  *      the value 4294967295 (2^32-1) is assumed.  If start is
  61  *      omitted, start is read from standard input.
  62  *
  63  * validation check: there are 664579 primes between 0 and 10^7
  64  */
  65
  66 #include <ctype.h>
  67 #include <err.h>
  68 #include <errno.h>
  69 #include <limits.h>
  70 #include <math.h>
  71 #include <memory.h>
  72 #include <stdio.h>
  73 #include <stdlib.h>
  74 #include <unistd.h>
  75
  76 #include "primes.h"
  77
  78 /*
  79  * Eratosthenes sieve table
  80  *
  81  * We only sieve the odd numbers.  The base of our sieve windows are always
  82  * odd.  If the base of table is 1, table[i] represents 2*i-1.  After the
  83  * sieve, table[i] == 1 if and only iff 2*i-1 is prime.
  84  *
  85  * We make TABSIZE large to reduce the overhead of inner loop setup.
  86  */
  87 static char table[TABSIZE];      /* Eratosthenes sieve of odd numbers */
  88
  89 /*
  90  * prime[i] is the (i-1)th prime.
  91  *
  92  * We are able to sieve 2^32-1 because this byte table yields all primes
  93  * up to 65537 and 65537^2 > 2^32-1.
  94  */
  95 extern const ubig prime[];
  96 extern const ubig *pr_limit;            /* largest prime in the prime array */
  97
  98 /*
  99  * To avoid excessive sieves for small factors, we use the table below to
 100  * setup our sieve blocks.  Each element represents a odd number starting
 101  * with 1.  All non-zero elements are factors of 3, 5, 7, 11 and 13.
 102  */
 103 extern const char pattern[];
 104 extern const int pattern_size;  /* length of pattern array */
 105
 106 static int dflag;
 107
 108 static void primes(ubig, ubig);
 109 static ubig read_num_buf(void);
 110 static void usage(void) __dead;
 111
 112 int
 113 main(int argc, char *argv[])
 114 {
 115         ubig start;             /* where to start generating */
 116         ubig stop;              /* don't generate at or above this value */
 117         int ch;
 118         char *p;
 119
 120         while ((ch = getopt(argc, argv, "d")) != -1)
 121                 switch (ch) {
 122                 case 'd':
 123                         dflag++;
 124                         break;
 125                 case '?':
 126                 default:
 127                         usage();
 128                 }
 129         argc -= optind;
 130         argv += optind;
 131
 132         start = 0;
 133         stop = BIG;
 134
 135         /*
 136          * Convert low and high args.  Strtoul(3) sets errno to
 137          * ERANGE if the number is too large, but, if there's
 138          * a leading minus sign it returns the negation of the
 139          * result of the conversion, which we'd rather disallow.
 140          */
 141         switch (argc) {
 142         case 2:
 143                 /* Start and stop supplied on the command line. */
 144                 if (argv[0][0] == '-' || argv[1][0] == '-')
 145                         errx(1, "negative numbers aren't permitted.");
 146
 147                 errno = 0;
 148                 start = strtoul(argv[0], &p, 10);
 149                 if (errno)
 150                         err(1, "%s", argv[0]);
 151                 if (*p != '\0')
 152                         errx(1, "%s: illegal numeric format.", argv[0]);
 153
 154                 errno = 0;
 155                 stop = strtoul(argv[1], &p, 10);
 156                 if (errno)
 157                         err(1, "%s", argv[1]);
 158                 if (*p != '\0')
 159                         errx(1, "%s: illegal numeric format.", argv[1]);
 160                 break;
 161         case 1:
 162                 /* Start on the command line. */
 163                 if (argv[0][0] == '-')
 164                         errx(1, "negative numbers aren't permitted.");
 165
 166                 errno = 0;
 167                 start = strtoul(argv[0], &p, 10);
 168                 if (errno)
 169                         err(1, "%s", argv[0]);
 170                 if (*p != '\0')
 171                         errx(1, "%s: illegal numeric format.", argv[0]);
 172                 break;
 173         case 0:
 174                 start = read_num_buf();
 175                 break;
 176         default:
 177                 usage();
 178         }
 179
 180         if (start > stop)
 181                 errx(1, "start value must be less than stop value.");
 182         primes(start, stop);
 183         exit(0);
 184 }
 185
 186 /*
 187  * read_num_buf --
 188  *      This routine returns a number n, where 0 <= n && n <= BIG.
 189  */
 190 ubig
 191 read_num_buf(void)
 192 {
 193         ubig val;
 194         char *p, buf[100];              /* > max number of digits. */
 195
 196         for (;;) {
 197                 if (fgets(buf, sizeof(buf), stdin) == NULL) {
 198                         if (ferror(stdin))
 199                                 err(1, "stdin");
 200                         exit(0);
 201                 }
 202                 for (p = buf; isblank(*p); ++p);
 203                 if (*p == '\n' || *p == '\0')
 204                         continue;
 205                 if (*p == '-')
 206                         errx(1, "negative numbers aren't permitted.");
 207                 errno = 0;
 208                 val = strtoul(buf, &p, 10);
 209                 if (errno)
 210                         err(1, "%s", buf);
 211                 if (*p != '\n')
 212                         errx(1, "%s: illegal numeric format.", buf);
 213                 return (val);
 214         }
 215 }
 216
 217 /*
 218  * primes - sieve and print primes from start up to and but not including stop
 219  *
 220  *      start   where to start generating
 221  *      stop    don't generate at or above this value
 222  */
 223 void
 224 primes(ubig start, ubig stop)
 225 {
 226         char *q;                /* sieve spot */
 227         ubig factor;            /* index and factor */
 228         char *tab_lim;          /* the limit to sieve on the table */
 229         const ubig *p;          /* prime table pointer */
 230         ubig fact_lim;          /* highest prime for current block */
 231         ubig mod;               /* temp storage for mod */
 232         ubig prev = 0;
 233
 234         /*
 235          * A number of systems can not convert double values into unsigned
 236          * longs when the values are larger than the largest signed value.
 237          * We don't have this problem, so we can go all the way to BIG.
 238          */
 239         if (start < 3) {
 240                 start = (ubig)2;
 241         }
 242         if (stop < 3) {
 243                 stop = (ubig)2;
 244         }
 245         if (stop <= start) {
 246                 return;
 247         }
 248
 249         /*
 250          * be sure that the values are odd, or 2
 251          */
 252         if (start != 2 && (start&0x1) == 0) {
 253                 ++start;
 254         }
 255         if (stop != 2 && (stop&0x1) == 0) {
 256                 ++stop;
 257         }
 258
 259         /*
 260          * quick list of primes <= pr_limit
 261          */
 262         if (start <= *pr_limit) {
 263                 /* skip primes up to the start value */
 264                 for (p = &prime[0], factor = prime[0];
 265                     factor < stop && p <= pr_limit; factor = *(++p)) {
 266                         if (factor >= start) {
 267                                 printf("%lu", (unsigned long) factor);
 268                                 if (dflag) {
 269                                         printf(" (%lu)",
 270                                             (unsigned long) factor - prev);
 271                                 }
 272                                 putchar('\n');
 273                         }
 274                         prev = factor;
 275                 }
 276                 /* return early if we are done */
 277                 if (p <= pr_limit) {
 278                         return;
 279                 }
 280                 start = *pr_limit+2;
 281         }
 282
 283         /*
 284          * we shall sieve a bytemap window, note primes and move the window
 285          * upward until we pass the stop point
 286          */
 287         while (start < stop) {
 288                 /*
 289                  * factor out 3, 5, 7, 11 and 13
 290                  */
 291                 /* initial pattern copy */
 292                 factor = (start%(2*3*5*7*11*13))/2; /* starting copy spot */
 293                 memcpy(table, &pattern[factor], pattern_size-factor);
 294                 /* main block pattern copies */
 295                 for (fact_lim=pattern_size-factor;
 296                     fact_lim+pattern_size<=TABSIZE; fact_lim+=pattern_size) {
 297                         memcpy(&table[fact_lim], pattern, pattern_size);
 298                 }
 299                 /* final block pattern copy */
 300                 memcpy(&table[fact_lim], pattern, TABSIZE-fact_lim);
 301
 302                 /*
 303                  * sieve for primes 17 and higher
 304                  */
 305                 /* note highest useful factor and sieve spot */
 306                 if (stop-start > TABSIZE+TABSIZE) {
 307                         tab_lim = &table[TABSIZE]; /* sieve it all */
 308                         fact_lim = (int)sqrt(
 309                                         (double)(start)+TABSIZE+TABSIZE+1.0);
 310                 } else {
 311                         tab_lim = &table[(stop-start)/2]; /* partial sieve */
 312                         fact_lim = (int)sqrt((double)(stop)+1.0);
 313                 }
 314                 /* sieve for factors >= 17 */
 315                 factor = 17;    /* 17 is first prime to use */
 316                 p = &prime[7];  /* 19 is next prime, pi(19)=7 */
 317                 do {
 318                         /* determine the factor's initial sieve point */
 319                         mod = start%factor;
 320                         if (mod & 0x1) {
 321                                 q = &table[(factor-mod)/2];
 322                         } else {
 323                                 q = &table[mod ? factor-(mod/2) : 0];
 324                         }
 325                         /* sieve for our current factor */
 326                         for ( ; q < tab_lim; q += factor) {
 327                                 *q = '\0'; /* sieve out a spot */
 328                         }
 329                 } while ((factor=(ubig)(*(p++))) <= fact_lim);
 330
 331                 /*
 332                  * print generated primes
 333                  */
 334                 for (q = table; q < tab_lim; ++q, start+=2) {
 335                         if (*q) {
 336                                 printf("%lu", (unsigned long) start);
 337                                 if (dflag) {
 338                                         printf(" (%lu)",
 339                                             (unsigned long) start - prev);
 340                                         prev = start;
 341                                 }
 342                                 putchar('\n');
 343                         }
 344                 }
 345         }
 346 }
 347
 348 void
 349 usage(void)
 350 {
 351         (void)fprintf(stderr, "usage: primes [-d] [start [stop]]\n");
 352         exit(1);
 353 }