stk/Mp/gmp-1.3.2/mpz_mul.c

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1996-09-27 06:29:02 -04:00
/* mpz_mul -- Multiply two integers.
Copyright (C) 1991 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library 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.
The GNU MP Library 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 the GNU MP Library; see the file COPYING. If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
#include "gmp.h"
#include "gmp-impl.h"
#ifndef BERKELEY_MP
void
#ifdef __STDC__
mpz_mul (MP_INT *w, const MP_INT *u, const MP_INT *v)
#else
mpz_mul (w, u, v)
MP_INT *w;
const MP_INT *u;
const MP_INT *v;
#endif
#else /* BERKELEY_MP */
void
#ifdef __STDC__
mult (const MP_INT *u, const MP_INT *v, MP_INT *w)
#else
mult (u, v, w)
const MP_INT *u;
const MP_INT *v;
MP_INT *w;
#endif
#endif /* BERKELEY_MP */
{
mp_size usize = u->size;
mp_size vsize = v->size;
mp_size wsize;
mp_size sign_product;
mp_ptr up, vp;
mp_ptr wp;
mp_ptr free_me = NULL;
size_t free_me_size;
sign_product = usize ^ vsize;
usize = ABS (usize);
vsize = ABS (vsize);
if (usize < vsize)
{
/* Swap U and V. */
{const MP_INT *t = u; u = v; v = t;}
{mp_size t = usize; usize = vsize; vsize = t;}
}
up = u->d;
vp = v->d;
wp = w->d;
/* Ensure W has space enough to store the result. */
wsize = usize + vsize;
if (w->alloc < wsize)
{
if (wp == up || wp == vp)
{
free_me = wp;
free_me_size = w->alloc;
}
else
(*_mp_free_func) (wp, w->alloc * BYTES_PER_MP_LIMB);
w->alloc = wsize;
wp = (mp_ptr) (*_mp_allocate_func) (wsize * BYTES_PER_MP_LIMB);
w->d = wp;
}
else
{
/* Make U and V not overlap with W. */
if (wp == up)
{
/* W and U are identical. Allocate temporary space for U. */
up = (mp_ptr) alloca (usize * BYTES_PER_MP_LIMB);
/* Is V identical too? Keep it identical with U. */
if (wp == vp)
vp = up;
/* Copy to the temporary space. */
MPN_COPY (up, wp, usize);
}
else if (wp == vp)
{
/* W and V are identical. Allocate temporary space for V. */
vp = (mp_ptr) alloca (vsize * BYTES_PER_MP_LIMB);
/* Copy to the temporary space. */
MPN_COPY (vp, wp, vsize);
}
}
wsize = mpn_mul (wp, up, usize, vp, vsize);
w->size = sign_product < 0 ? -wsize : wsize;
if (free_me != NULL)
(*_mp_free_func) (free_me, free_me_size * BYTES_PER_MP_LIMB);
alloca (0);
}