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/* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/* All Rights Reserved */
/*
* Copyright (c) 1980 Regents of the University of California.
* All rights reserved. The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*/
/* Portions Copyright(c) 1988, Sun Microsystems Inc. */
/* All Rights Reserved */
/*
* Copyright (c) 1997, by Sun Microsystems, Inc.
* All rights reserved.
*/
#ident "%Z%%M% %I% %E% SMI" /* SVr4.0 1.1 */
/* LINTLIBRARY */
#include <mp.h>
#include "libmp.h"
#include <sys/types.h>
void
mp_gcd(MINT *a, MINT *b, MINT *c)
{
MINT x, y, z, w;
x.len = y.len = z.len = w.len = 0;
_mp_move(a, &x);
_mp_move(b, &y);
while (y.len != 0) {
mp_mdiv(&x, &y, &w, &z);
_mp_move(&y, &x);
_mp_move(&z, &y);
}
_mp_move(&x, c);
_mp_xfree(&x);
_mp_xfree(&y);
_mp_xfree(&z);
_mp_xfree(&w);
}
void
mp_invert(MINT *x1, MINT *x0, MINT *c)
{
MINT u2, u3;
MINT v2, v3;
MINT zero;
MINT q, r;
MINT t;
MINT x0_prime;
static MINT *one = NULL;
/*
* Minimize calls to allocators. Don't use pointers for local
* variables, for the one "initialized" multiple precision
* variable, do it just once.
*/
if (one == NULL)
one = mp_itom(1);
zero.len = q.len = r.len = t.len = 0;
x0_prime.len = u2.len = u3.len = 0;
_mp_move(x0, &u3);
_mp_move(x0, &x0_prime);
v2.len = v3.len = 0;
_mp_move(one, &v2);
_mp_move(x1, &v3);
while (mp_mcmp(&v3, &zero) != 0) {
/* invariant: x0*u1 + x1*u2 = u3 */
/* invariant: x0*v1 + x2*v2 = v3 */
/* invariant: x(n+1) = x(n-1) % x(n) */
mp_mdiv(&u3, &v3, &q, &r);
_mp_move(&v3, &u3);
_mp_move(&r, &v3);
mp_mult(&q, &v2, &t);
mp_msub(&u2, &t, &t);
_mp_move(&v2, &u2);
_mp_move(&t, &v2);
}
/* now x0*u1 + x1*u2 == 1, therefore, (u2*x1) % x0 == 1 */
_mp_move(&u2, c);
if (mp_mcmp(c, &zero) < 0) {
mp_madd(&x0_prime, c, c);
}
_mp_xfree(&zero);
_mp_xfree(&v2);
_mp_xfree(&v3);
_mp_xfree(&u2);
_mp_xfree(&u3);
_mp_xfree(&q);
_mp_xfree(&r);
_mp_xfree(&t);
}
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