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34 * primes - generate a table of primes between two values
36 * By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo
38 * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\
41 * primes [-h] [start [stop]]
43 * Print primes >= start and < stop. If stop is omitted,
44 * the value 18446744073709551615 (2^64-1) is assumed. If
45 * start is omitted, start is read from standard input.
47 * validation check: there are 664579 primes between 0 and 10^7
50 #include <capsicum_helpers.h>
66 * Eratosthenes sieve table
68 * We only sieve the odd numbers. The base of our sieve windows are always
69 * odd. If the base of table is 1, table[i] represents 2*i-1. After the
70 * sieve, table[i] == 1 if and only if 2*i-1 is prime.
72 * We make TABSIZE large to reduce the overhead of inner loop setup.
74 static char table[TABSIZE]; /* Eratosthenes sieve of odd numbers */
78 static void primes(ubig, ubig);
79 static ubig read_num_buf(void);
80 static void usage(void);
83 main(int argc, char *argv[])
85 ubig start; /* where to start generating */
86 ubig stop; /* don't generate at or above this value */
90 caph_cache_catpages();
94 while ((ch = getopt(argc, argv, "h")) != -1)
107 stop = (uint64_t)(-1);
110 * Convert low and high args. Strtoumax(3) sets errno to
111 * ERANGE if the number is too large, but, if there's
112 * a leading minus sign it returns the negation of the
113 * result of the conversion, which we'd rather disallow.
117 /* Start and stop supplied on the command line. */
118 if (argv[0][0] == '-' || argv[1][0] == '-')
119 errx(1, "negative numbers aren't permitted.");
122 start = strtoumax(argv[0], &p, 0);
124 err(1, "%s", argv[0]);
126 errx(1, "%s: illegal numeric format.", argv[0]);
129 stop = strtoumax(argv[1], &p, 0);
131 err(1, "%s", argv[1]);
133 errx(1, "%s: illegal numeric format.", argv[1]);
136 /* Start on the command line. */
137 if (argv[0][0] == '-')
138 errx(1, "negative numbers aren't permitted.");
141 start = strtoumax(argv[0], &p, 0);
143 err(1, "%s", argv[0]);
145 errx(1, "%s: illegal numeric format.", argv[0]);
148 start = read_num_buf();
155 errx(1, "start value must be less than stop value.");
162 * This routine returns a number n, where 0 <= n && n <= BIG.
168 char *p, buf[LINE_MAX]; /* > max number of digits. */
171 if (fgets(buf, sizeof(buf), stdin) == NULL) {
176 for (p = buf; isblank(*p); ++p);
177 if (*p == '\n' || *p == '\0')
180 errx(1, "negative numbers aren't permitted.");
182 val = strtoumax(buf, &p, 0);
186 errx(1, "%s: illegal numeric format.", buf);
192 * primes - sieve and print primes from start up to and but not including stop
195 primes(ubig start, ubig stop)
197 char *q; /* sieve spot */
198 ubig factor; /* index and factor */
199 char *tab_lim; /* the limit to sieve on the table */
200 const ubig *p; /* prime table pointer */
201 ubig fact_lim; /* highest prime for current block */
202 ubig mod; /* temp storage for mod */
205 * A number of systems can not convert double values into unsigned
206 * longs when the values are larger than the largest signed value.
207 * We don't have this problem, so we can go all the way to BIG.
220 * be sure that the values are odd, or 2
222 if (start != 2 && (start&0x1) == 0) {
225 if (stop != 2 && (stop&0x1) == 0) {
230 * quick list of primes <= pr_limit
232 if (start <= *pr_limit) {
233 /* skip primes up to the start value */
234 for (p = &prime[0], factor = prime[0];
235 factor < stop && p <= pr_limit; factor = *(++p)) {
236 if (factor >= start) {
237 printf(hflag ? "%" PRIx64 "\n" : "%" PRIu64 "\n", factor);
240 /* return early if we are done */
248 * we shall sieve a bytemap window, note primes and move the window
249 * upward until we pass the stop point
251 while (start < stop) {
253 * factor out 3, 5, 7, 11 and 13
255 /* initial pattern copy */
256 factor = (start%(2*3*5*7*11*13))/2; /* starting copy spot */
257 memcpy(table, &pattern[factor], pattern_size-factor);
258 /* main block pattern copies */
259 for (fact_lim=pattern_size-factor;
260 fact_lim+pattern_size<=TABSIZE; fact_lim+=pattern_size) {
261 memcpy(&table[fact_lim], pattern, pattern_size);
263 /* final block pattern copy */
264 memcpy(&table[fact_lim], pattern, TABSIZE-fact_lim);
267 * sieve for primes 17 and higher
269 /* note highest useful factor and sieve spot */
270 if (stop-start > TABSIZE+TABSIZE) {
271 tab_lim = &table[TABSIZE]; /* sieve it all */
272 fact_lim = sqrt(start+1.0+TABSIZE+TABSIZE);
274 tab_lim = &table[(stop-start)/2]; /* partial sieve */
275 fact_lim = sqrt(stop+1.0);
277 /* sieve for factors >= 17 */
278 factor = 17; /* 17 is first prime to use */
279 p = &prime[7]; /* 19 is next prime, pi(19)=7 */
281 /* determine the factor's initial sieve point */
284 q = &table[(factor-mod)/2];
286 q = &table[mod ? factor-(mod/2) : 0];
288 /* sive for our current factor */
289 for ( ; q < tab_lim; q += factor) {
290 *q = '\0'; /* sieve out a spot */
293 } while (factor <= fact_lim);
296 * print generated primes
298 for (q = table; q < tab_lim; ++q, start+=2) {
300 if (start > SIEVEMAX) {
304 printf(hflag ? "%" PRIx64 "\n" : "%" PRIu64 "\n", start);
313 fprintf(stderr, "usage: primes [-h] [start [stop]]\n");