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/* mpf_add -- Add two floats.
Copyright (C) 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"
void
#if __STDC__
mpf_add (mpf_ptr r, mpf_srcptr u, mpf_srcptr v)
#else
mpf_add (r, u, v)
mpf_ptr r;
mpf_srcptr u;
mpf_srcptr v;
#endif
{
mp_srcptr up, vp;
mp_ptr rp, tp;
mp_size_t usize, vsize, rsize;
mp_size_t prec;
mp_exp_t uexp;
mp_size_t ediff;
mp_limb_t cy;
int negate;
TMP_DECL (marker);
usize = u->_mp_size;
vsize = v->_mp_size;
/* Handle special cases that don't work in generic code below. */
if (usize == 0)
{
mpf_set (r, v);
return;
}
if (vsize == 0)
{
mpf_set (r, u);
return;
}
/* If signs of U and V are different, perform subtraction. */
if ((usize ^ vsize) < 0)
{
__mpf_struct v_negated;
v_negated._mp_size = -vsize;
v_negated._mp_exp = v->_mp_exp;
v_negated._mp_d = v->_mp_d;
mpf_sub (r, u, &v_negated);
return;
}
TMP_MARK (marker);
/* Signs are now known to be the same. */
negate = usize < 0;
/* Make U be the operand with the largest exponent. */
if (u->_mp_exp < v->_mp_exp)
{
mpf_srcptr t;
t = u; u = v; v = t;
usize = u->_mp_size;
vsize = v->_mp_size;
}
usize = ABS (usize);
vsize = ABS (vsize);
up = u->_mp_d;
vp = v->_mp_d;
rp = r->_mp_d;
prec = r->_mp_prec;
uexp = u->_mp_exp;
ediff = u->_mp_exp - v->_mp_exp;
/* If U extends beyond PREC, ignore the part that does. */
if (usize > prec)
{
up += usize - prec;
usize = prec;
}
/* If V extends beyond PREC, ignore the part that does.
Note that this may make vsize negative. */
if (vsize + ediff > prec)
{
vp += vsize + ediff - prec;
vsize = prec - ediff;
}
#if 0
/* Locate the least significant non-zero limb in (the needed parts
of) U and V, to simplify the code below. */
while (up[0] == 0)
up++, usize--;
while (vp[0] == 0)
vp++, vsize--;
#endif
/* Allocate temp space for the result. Allocate
just vsize + ediff later??? */
tp = (mp_ptr) TMP_ALLOC (prec * BYTES_PER_MP_LIMB);
if (ediff >= prec)
{
/* V completely cancelled. */
if (tp != up)
MPN_COPY (rp, up, usize);
rsize = usize;
}
else
{
/* uuuu | uuuu | uuuu | uuuu | uuuu */
/* vvvvvvv | vv | vvvvv | v | vv */
if (usize > ediff)
{
/* U and V partially overlaps. */
if (vsize + ediff <= usize)
{
/* uuuu */
/* v */
mp_size_t size;
size = usize - ediff - vsize;
MPN_COPY (tp, up, size);
cy = mpn_add (tp + size, up + size, usize - size, vp, vsize);
rsize = usize;
}
else
{
/* uuuu */
/* vvvvv */
mp_size_t size;
size = vsize + ediff - usize;
MPN_COPY (tp, vp, size);
cy = mpn_add (tp + size, up, usize, vp + size, usize - ediff);
rsize = vsize + ediff;
}
}
else
{
/* uuuu */
/* vv */
mp_size_t size;
size = vsize + ediff - usize;
MPN_COPY (tp, vp, vsize);
MPN_ZERO (tp + vsize, ediff - usize);
MPN_COPY (tp + size, up, usize);
cy = 0;
rsize = size + usize;
}
MPN_COPY (rp, tp, rsize);
rp[rsize] = cy;
rsize += cy;
uexp += cy;
}
r->_mp_size = negate ? -rsize : rsize;
r->_mp_exp = uexp;
TMP_FREE (marker);
}
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