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/* mpz_sub -- Subtract two integers.
Copyright (C) 1991, 1993, 1994, 1996 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 Library General Public License as published by
the Free Software Foundation; either version 2 of the License, 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 Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include "gmp.h"
#include "gmp-impl.h"
#ifndef BERKELEY_MP
void
#if __STDC__
mpz_sub (mpz_ptr w, mpz_srcptr u, mpz_srcptr v)
#else
mpz_sub (w, u, v)
mpz_ptr w;
mpz_srcptr u;
mpz_srcptr v;
#endif
#else /* BERKELEY_MP */
void
#if __STDC__
msub (mpz_srcptr u, mpz_srcptr v, mpz_ptr w)
#else
msub (u, v, w)
mpz_srcptr u;
mpz_srcptr v;
mpz_ptr w;
#endif
#endif /* BERKELEY_MP */
{
mp_srcptr up, vp;
mp_ptr wp;
mp_size_t usize, vsize, wsize;
mp_size_t abs_usize;
mp_size_t abs_vsize;
usize = u->_mp_size;
vsize = -v->_mp_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 __mpz_struct *t = u; u = v; v = t;}
{mp_size_t t = usize; usize = vsize; vsize = t;}
{mp_size_t t = abs_usize; abs_usize = abs_vsize; abs_vsize = t;}
}
/* True: ABS_USIZE >= ABS_VSIZE. */
/* If not space for w (and possible carry), increase space. */
wsize = abs_usize + 1;
if (w->_mp_alloc < wsize)
_mpz_realloc (w, wsize);
/* These must be after realloc (u or v may be the same as w). */
up = u->_mp_d;
vp = v->_mp_d;
wp = w->_mp_d;
if ((usize ^ vsize) < 0)
{
/* U and V have different sign. Need to compare them to determine
which operand to subtract from which. */
/* This test is right since ABS_USIZE >= ABS_VSIZE. */
if (abs_usize != abs_vsize)
{
mpn_sub (wp, up, abs_usize, vp, abs_vsize);
wsize = abs_usize;
MPN_NORMALIZE (wp, wsize);
if (usize < 0)
wsize = -wsize;
}
else if (mpn_cmp (up, vp, abs_usize) < 0)
{
mpn_sub_n (wp, vp, up, abs_usize);
wsize = abs_usize;
MPN_NORMALIZE (wp, wsize);
if (usize >= 0)
wsize = -wsize;
}
else
{
mpn_sub_n (wp, up, vp, abs_usize);
wsize = abs_usize;
MPN_NORMALIZE (wp, wsize);
if (usize < 0)
wsize = -wsize;
}
}
else
{
/* U and V have same sign. Add them. */
mp_limb_t cy_limb = mpn_add (wp, up, abs_usize, vp, abs_vsize);
wp[abs_usize] = cy_limb;
wsize = abs_usize + cy_limb;
if (usize < 0)
wsize = -wsize;
}
w->_mp_size = wsize;
}
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