primes/primes.c

   1 /*      $NetBSD: primes.c,v 1.22 2018/02/03 15:40:29 christos 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 1.22 2018/02/03 15:40:29 christos 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, http://www.isthe.com/chongo/index.html /\oo/\
  53  *
  54  * usage:
  55  *      primes [-dh] [start [stop]]
  56  *
  57  *      Print primes >= start and < stop.  If stop is omitted,
  58  *      the value SPSPMAX is assumed.  If start is
  59  *      omitted, start is read from standard input.
  60  *              -d: print difference to previous prime, e.g. 3 (1)
  61  *              -h: print primes in hexadecimal
  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 <inttypes.h>
  70 #include <limits.h>
  71 #include <math.h>
  72 #include <stdio.h>
  73 #include <stdlib.h>
  74 #include <string.h>
  75 #include <unistd.h>
  76
  77 #include "primes.h"
  78
  79 /*
  80  * Eratosthenes sieve table
  81  *
  82  * We only sieve the odd numbers.  The base of our sieve windows are always
  83  * odd.  If the base of table is 1, table[i] represents 2*i-1.  After the
  84  * sieve, table[i] == 1 if and only if 2*i-1 is prime.
  85  *
  86  * We make TABSIZE large to reduce the overhead of inner loop setup.
  87  */
  88 static char table[TABSIZE];      /* Eratosthenes sieve of odd numbers */
  89
  90 static int dflag, hflag;
  91
  92 static void primes(uint64_t, uint64_t);
  93 static uint64_t read_num_buf(void);
  94 static void usage(void) __dead;
  95
  96
  97 int
  98 main(int argc, char *argv[])
  99 {
 100         uint64_t start;         /* where to start generating */
 101         uint64_t stop;          /* don't generate at or above this value */
 102         int ch;
 103         char *p;
 104
 105         while ((ch = getopt(argc, argv, "dh")) != -1)
 106                 switch (ch) {
 107                 case 'd':
 108                         dflag++;
 109                         break;
 110                 case 'h':
 111                         hflag++;
 112                         break;
 113                 case '?':
 114                 default:
 115                         usage();
 116                 }
 117         argc -= optind;
 118         argv += optind;
 119
 120         start = 0;
 121         stop = (uint64_t)(-1);
 122
 123         /*
 124          * Convert low and high args.  Strtoumax(3) sets errno to
 125          * ERANGE if the number is too large, but, if there's
 126          * a leading minus sign it returns the negation of the
 127          * result of the conversion, which we'd rather disallow.
 128          */
 129         switch (argc) {
 130         case 2:
 131                 /* Start and stop supplied on the command line. */
 132                 if (argv[0][0] == '-' || argv[1][0] == '-')
 133                         errx(1, "negative numbers aren't permitted.");
 134
 135                 errno = 0;
 136                 start = strtoumax(argv[0], &p, 0);
 137                 if (errno)
 138                         err(1, "%s", argv[0]);
 139                 if (*p != '\0')
 140                         errx(1, "%s: illegal numeric format.", argv[0]);
 141
 142                 errno = 0;
 143                 stop = strtoumax(argv[1], &p, 0);
 144                 if (errno)
 145                         err(1, "%s", argv[1]);
 146                 if (*p != '\0')
 147                         errx(1, "%s: illegal numeric format.", argv[1]);
 148                 break;
 149         case 1:
 150                 /* Start on the command line. */
 151                 if (argv[0][0] == '-')
 152                         errx(1, "negative numbers aren't permitted.");
 153
 154                 errno = 0;
 155                 start = strtoumax(argv[0], &p, 0);
 156                 if (errno)
 157                         err(1, "%s", argv[0]);
 158                 if (*p != '\0')
 159                         errx(1, "%s: illegal numeric format.", argv[0]);
 160                 break;
 161         case 0:
 162                 start = read_num_buf();
 163                 break;
 164         default:
 165                 usage();
 166         }
 167
 168         if (start > stop)
 169                 errx(1, "start value must be less than stop value.");
 170         primes(start, stop);
 171         return (0);
 172 }
 173
 174 /*
 175  * read_num_buf --
 176  *      This routine returns a number n, where 0 <= n && n <= ULONG_MAX.
 177  */
 178 static uint64_t
 179 read_num_buf(void)
 180 {
 181         uint64_t val;
 182         char *p, buf[LINE_MAX];         /* > max number of digits. */
 183
 184         for (;;) {
 185                 if (fgets(buf, sizeof(buf), stdin) == NULL) {
 186                         if (ferror(stdin))
 187                                 err(1, "stdin");
 188                         exit(0);
 189                 }
 190                 for (p = buf; isblank((unsigned char)*p); ++p);
 191                 if (*p == '\n' || *p == '\0')
 192                         continue;
 193                 if (*p == '-')
 194                         errx(1, "negative numbers aren't permitted.");
 195                 errno = 0;
 196                 val = strtoumax(buf, &p, 0);
 197                 if (errno)
 198                         err(1, "%s", buf);
 199                 if (*p != '\n')
 200                         errx(1, "%s: illegal numeric format.", buf);
 201                 return (val);
 202         }
 203 }
 204
 205 /*
 206  * primes - sieve and print primes from start up to and but not including stop
 207  */
 208 static void
 209 primes(uint64_t start, uint64_t stop)
 210 {
 211         char *q;                /* sieve spot */
 212         uint64_t factor;        /* index and factor */
 213         char *tab_lim;          /* the limit to sieve on the table */
 214         const uint64_t *p;      /* prime table pointer */
 215         uint64_t fact_lim;      /* highest prime for current block */
 216         uint64_t mod;           /* temp storage for mod */
 217         uint64_t prev = 0;
 218
 219         /*
 220          * A number of systems can not convert double values into unsigned
 221          * longs when the values are larger than the largest signed value.
 222          * We don't have this problem, so we can go all the way to ULONG_MAX.
 223          */
 224         if (start < 3) {
 225                 start = 2;
 226         }
 227         if (stop < 3) {
 228                 stop = 2;
 229         }
 230         if (stop <= start) {
 231                 return;
 232         }
 233
 234         /*
 235          * be sure that the values are odd, or 2
 236          */
 237         if (start != 2 && (start&0x1) == 0) {
 238                 ++start;
 239         }
 240         if (stop != 2 && (stop&0x1) == 0) {
 241                 ++stop;
 242         }
 243
 244         /*
 245          * quick list of primes <= pr_limit
 246          */
 247         if (start <= *pr_limit) {
 248                 /* skip primes up to the start value */
 249                 for (p = &prime[0], factor = prime[0];
 250                     factor < stop && p <= pr_limit; factor = *(++p)) {
 251                         if (factor >= start) {
 252                                 printf(hflag ? "%" PRIx64 : "%" PRIu64, factor);
 253                                 if (dflag) {
 254                                         printf(" (%" PRIu64 ")", factor - prev);
 255                                 }
 256                                 putchar('\n');
 257                         }
 258                         prev = factor;
 259                 }
 260                 /* return early if we are done */
 261                 if (p <= pr_limit) {
 262                         return;
 263                 }
 264                 start = *pr_limit+2;
 265         }
 266
 267         /*
 268          * we shall sieve a bytemap window, note primes and move the window
 269          * upward until we pass the stop point
 270          */
 271         while (start < stop) {
 272                 /*
 273                  * factor out 3, 5, 7, 11 and 13
 274                  */
 275                 /* initial pattern copy */
 276                 factor = (start%(2*3*5*7*11*13))/2; /* starting copy spot */
 277                 memcpy(table, &pattern[factor], pattern_size-factor);
 278                 /* main block pattern copies */
 279                 for (fact_lim=pattern_size-factor;
 280                     fact_lim+pattern_size<=TABSIZE; fact_lim+=pattern_size) {
 281                         memcpy(&table[fact_lim], pattern, pattern_size);
 282                 }
 283                 /* final block pattern copy */
 284                 memcpy(&table[fact_lim], pattern, TABSIZE-fact_lim);
 285
 286                 /*
 287                  * sieve for primes 17 and higher
 288                  */
 289                 /* note highest useful factor and sieve spot */
 290                 if (stop-start > TABSIZE+TABSIZE) {
 291                         tab_lim = &table[TABSIZE]; /* sieve it all */
 292                         fact_lim = sqrt(start+1.0+TABSIZE+TABSIZE);
 293                 } else {
 294                         tab_lim = &table[(stop-start)/2]; /* partial sieve */
 295                         fact_lim = sqrt(stop+1.0);
 296                 }
 297                 /* sieve for factors >= 17 */
 298                 factor = 17;    /* 17 is first prime to use */
 299                 p = &prime[7];  /* 19 is next prime, pi(19)=7 */
 300                 do {
 301                         /* determine the factor's initial sieve point */
 302                         mod = start%factor;
 303                         if (mod & 0x1) {
 304                                 q = &table[(factor-mod)/2];
 305                         } else {
 306                                 q = &table[mod ? factor-(mod/2) : 0];
 307                         }
 308                         /* sieve for our current factor */
 309                         for ( ; q < tab_lim; q += factor) {
 310                                 *q = '\0'; /* sieve out a spot */
 311                         }
 312                         factor = *p++;
 313                 } while (factor <= fact_lim);
 314
 315                 /*
 316                  * print generated primes
 317                  */
 318                 for (q = table; q < tab_lim; ++q, start+=2) {
 319                         if (*q) {
 320                                 if (start > SIEVEMAX) {
 321                                         if (!isprime(start))
 322                                                 continue;
 323                                 }
 324                                 printf(hflag ? "%" PRIx64 : "%" PRIu64, start);
 325                                 if (dflag && (prev || (start <= *pr_limit))) {
 326                                         printf(" (%" PRIu64 ")", start - prev);
 327                                 }
 328                                 putchar('\n');
 329                                 prev = start;
 330                         }
 331                 }
 332         }
 333 }
 334
 335 static void
 336 usage(void)
 337 {
 338         (void)fprintf(stderr, "usage: primes [-dh] [start [stop]]\n");
 339         exit(1);
 340 }