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/* $Id: mpz_square.C,v 1.1 1999/02/01 02:18:34 dm Exp $ */
/*
*
* Copyright (C) 1998 David Mazieres (dm@uun.org)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*/
#include "sysconf.h"
#include "gmp.h"
#undef ABS
#define ABS(a) ((a) < 0 ? -(a) : (a))
#ifdef __cplusplus
extern "C" void mpz_square (MP_INT *, const MP_INT *);
#endif /* __cplusplus */
void
mpz_square (MP_INT *res, const MP_INT *arg)
{
MP_INT tmp, *r;
if (!arg->_mp_size) {
res->_mp_size = 0;
return;
}
if (res == arg) {
r = &tmp;
mpz_init (r);
}
else
r = res;
int asize = ABS (arg->_mp_size);
const mp_limb_t *ap = arg->_mp_d;
int rsize = 2 * asize;
if (r->_mp_alloc < rsize)
_mpz_realloc (r, rsize);
mp_limb_t *rp = r->_mp_d;
if (asize < 24) {
/* This seems faster to be faster for small sizes. */
mpn_mul_n (rp, ap, ap, asize);
}
else {
bzero (rp, rsize * sizeof (mp_limb_t));
for (int i = 1; i < asize; i++) {
mp_limb_t *mrp = rp + (i<<1) - 1;
mrp[asize - i] = mpn_addmul_1 (mrp, ap + i, asize - i, ap[i - 1]);
}
mpn_lshift (rp, rp, rsize, 1);
for (int i = 0; i < asize; i++) {
mp_size_t rpos = i << 1;
mp_limb_t c = mpn_addmul_1 (rp + rpos, &ap[i], 1, ap[i]);
mpn_add_1 (rp + rpos + 1, rp + rpos + 1, rsize - rpos - 1, c);
}
}
while (rsize && !rp[rsize - 1])
rsize--;
r->_mp_size = rsize;
if (res == arg) {
mpz_clear (res);
*(MP_INT *) res = tmp;
}
}
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