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/* mpz_sub -- Subtract 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_sub (MP_INT *w, const MP_INT *u, const MP_INT *v)
#else
mpz_sub (w, u, v)
MP_INT *w;
const MP_INT *u;
const MP_INT *v;
#endif
#else /* BERKELEY_MP */
void
#ifdef __STDC__
msub (const MP_INT *u, const MP_INT *v, MP_INT *w)
#else
msub (u, v, w)
const MP_INT *u;
const MP_INT *v;
MP_INT *w;
#endif
#endif /* BERKELEY_MP */
{
mp_srcptr up, vp;
mp_ptr wp;
mp_size usize, vsize, wsize;
mp_size abs_usize;
mp_size abs_vsize;
usize = u->size;
vsize = -v->size; /* The "-" makes the difference from mpz_add */
abs_usize = ABS (usize);
abs_vsize = ABS (vsize);
if (abs_usize < abs_vsize)
{
/* Swap U and V. */
{const MP_INT *t = u; u = v; v = t;}
{mp_size t = usize; usize = vsize; vsize = t;}
{mp_size t = abs_usize; abs_usize = abs_vsize; abs_vsize = t;}
}
/* True: abs(USIZE) >= abs(VSIZE) */
/* If not space for sum (and possible carry), increase space. */
wsize = abs_usize + 1;
if (w->alloc < wsize)
_mpz_realloc (w, wsize);
/* These must be after realloc (u or v may be the same as w). */
up = u->d;
vp = v->d;
wp = w->d;
if (usize >= 0)
{
if (vsize >= 0)
{
wsize = mpn_add (wp, up, abs_usize, vp, abs_vsize);
if (wsize != 0)
wp[abs_usize] = 1;
wsize = wsize + abs_usize;
}
else
{
/* The signs are different. Need exact comparision to determine
which operand to subtract from which. */
if (abs_usize == abs_vsize && mpn_cmp (up, vp, abs_usize) < 0)
wsize = -(abs_usize + mpn_sub (wp, vp, abs_usize, up, abs_usize));
else
wsize = abs_usize + mpn_sub (wp, up, abs_usize, vp, abs_vsize);
}
}
else
{
if (vsize >= 0)
{
/* The signs are different. Need exact comparision to determine
which operand to subtract from which. */
if (abs_usize == abs_vsize && mpn_cmp (up, vp, abs_usize) < 0)
wsize = abs_usize + mpn_sub (wp, vp, abs_usize, up, abs_usize);
else
wsize = -(abs_usize + mpn_sub (wp, up, abs_usize, vp, abs_vsize));
}
else
{
wsize = mpn_add (wp, up, abs_usize, vp, abs_vsize);
if (wsize != 0)
wp[abs_usize] = 1;
wsize = -(wsize + abs_usize);
}
}
w->size = wsize;
}
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