138 lines
3.8 KiB
C
138 lines
3.8 KiB
C
/* $NetBSD: factor.c,v 1.7 1998/02/20 01:40:53 jonathan Exp $ */
|
|
|
|
/*
|
|
* Copyright 1997 Piermont Information Systems Inc.
|
|
* All rights reserved.
|
|
*
|
|
* Written by Philip A. Nelson for Piermont Information Systems Inc.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* 3. All advertising materials mentioning features or use of this software
|
|
* must display the following acknowledgement:
|
|
* This product includes software develooped for the NetBSD Project by
|
|
* Piermont Information Systems Inc.
|
|
* 4. The name of Piermont Information Systems Inc. may not be used to endorse
|
|
* or promote products derived from this software without specific prior
|
|
* written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY PIERMONT INFORMATION SYSTEMS INC. ``AS IS''
|
|
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL PIERMONT INFORMATION SYSTEMS INC. BE
|
|
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
|
|
* THE POSSIBILITY OF SUCH DAMAGE.
|
|
*
|
|
*/
|
|
|
|
#include <stdlib.h>
|
|
#include <stdio.h>
|
|
#include "defs.h"
|
|
|
|
/*
|
|
* primes - prime table, built to include up to 46345 because
|
|
* sqrt(2^31) = 46340.9500118415
|
|
*
|
|
* building the table instead of storing a precomputed table saves
|
|
* about 19K of space on the binary image.
|
|
*/
|
|
|
|
long primes[4800];
|
|
int num_primes = 2;
|
|
|
|
static void build_primes (long max)
|
|
{
|
|
long pc;
|
|
int j;
|
|
long rem;
|
|
|
|
/*
|
|
* Initialise primes at run-time rather than compile time
|
|
* so it's put in bss rather than data.
|
|
*/
|
|
primes[0] = 2;
|
|
primes[1] = 3;
|
|
|
|
for (pc = primes[num_primes-1]; pc < 46345 && pc*pc <= max; pc+=2) {
|
|
j = 0;
|
|
rem = 1;
|
|
while (j<num_primes && primes[j]*primes[j] <= pc) {
|
|
if ((rem = pc % primes[j]) == 0)
|
|
break;
|
|
j++;
|
|
}
|
|
if (rem)
|
|
primes[num_primes++] = pc;
|
|
}
|
|
}
|
|
|
|
/* factor: prepare a list of prime factors of val.
|
|
The last number may not be a prime factor is the list is not
|
|
long enough. */
|
|
|
|
void factor (long val, long *fact_list, int fact_size, int *num_fact)
|
|
{
|
|
int i;
|
|
|
|
/* Check to make sure we have enough primes. */
|
|
build_primes(val);
|
|
|
|
i = 0;
|
|
*num_fact = 0;
|
|
while (*num_fact < fact_size-1 && val > 1 && i < num_primes) {
|
|
/* Find the next prime that divides. */
|
|
while (i < num_primes && val % primes[i] != 0) i++;
|
|
|
|
/* Put factors in array. */
|
|
while (*num_fact < fact_size-1 && i < num_primes &&
|
|
val % primes[i] == 0) {
|
|
fact_list[(*num_fact)++] = primes[i];
|
|
val /= primes[i];
|
|
}
|
|
}
|
|
if (val > 1)
|
|
fact_list[(*num_fact)++] = val;
|
|
}
|
|
|
|
#ifdef TESTING
|
|
int
|
|
main(int argc, char **argv)
|
|
{
|
|
long facts[30];
|
|
long val;
|
|
int i, nfact;
|
|
int arg;
|
|
|
|
if (argc < 2) {
|
|
fprintf (stderr, "usage: %s numbers\n", argv[0]);
|
|
exit(1);
|
|
}
|
|
|
|
/* Factor each arg! */
|
|
for (arg = 1; arg < argc; arg++) {
|
|
|
|
val = atol(argv[arg]);
|
|
factor (val, facts, 30, &nfact);
|
|
|
|
printf ("%ld:", val);
|
|
for (i = 0; i<nfact; i++)
|
|
printf (" %ld", facts[i]);
|
|
printf ("\n");
|
|
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
#endif
|