mirror of
https://review.haiku-os.org/buildtools
synced 2025-02-01 02:54:39 +01:00
127 lines
3.5 KiB
C
127 lines
3.5 KiB
C
/* mpf_div -- Divide two floats.
|
|
|
|
Copyright 1993, 1994, 1996, 2000, 2001, 2002, 2004, 2005, 2010 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 Lesser General Public License as published by
|
|
the Free Software Foundation; either version 3 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 Lesser General Public
|
|
License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public License
|
|
along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
|
|
|
|
#include "gmp.h"
|
|
#include "gmp-impl.h"
|
|
|
|
|
|
/* Not done:
|
|
|
|
No attempt is made to identify an overlap u==v. The result will be
|
|
correct (1.0), but a full actual division is done whereas of course
|
|
x/x==1 needs no work. Such a call is not a sensible thing to make, and
|
|
it's left to an application to notice and optimize if it might arise
|
|
somehow through pointer aliasing or whatever.
|
|
|
|
Enhancements:
|
|
|
|
The high quotient limb is non-zero when high{up,vsize} >= {vp,vsize}. We
|
|
could make that comparison and use qsize==prec instead of qsize==prec+1,
|
|
to save one limb in the division.
|
|
|
|
If r==u but the size is enough bigger than prec that there won't be an
|
|
overlap between quotient and dividend in mpn_tdiv_qr, then we can avoid
|
|
copying up,usize. This would only arise from a prec reduced with
|
|
mpf_set_prec_raw and will be pretty unusual, but might be worthwhile if
|
|
it could be worked into the copy_u decision cleanly. */
|
|
|
|
void
|
|
mpf_div (mpf_ptr r, mpf_srcptr u, mpf_srcptr v)
|
|
{
|
|
mp_srcptr up, vp;
|
|
mp_ptr rp, tp, new_vp;
|
|
mp_size_t usize, vsize, rsize, prospective_rsize, tsize, zeros;
|
|
mp_size_t sign_quotient, prec, high_zero, chop;
|
|
mp_exp_t rexp;
|
|
int copy_u;
|
|
TMP_DECL;
|
|
|
|
usize = SIZ(u);
|
|
vsize = SIZ(v);
|
|
sign_quotient = usize ^ vsize;
|
|
usize = ABS (usize);
|
|
vsize = ABS (vsize);
|
|
prec = PREC(r);
|
|
|
|
if (vsize == 0)
|
|
DIVIDE_BY_ZERO;
|
|
|
|
if (usize == 0)
|
|
{
|
|
SIZ(r) = 0;
|
|
EXP(r) = 0;
|
|
return;
|
|
}
|
|
|
|
TMP_MARK;
|
|
rexp = EXP(u) - EXP(v) + 1;
|
|
|
|
rp = PTR(r);
|
|
up = PTR(u);
|
|
vp = PTR(v);
|
|
|
|
prospective_rsize = usize - vsize + 1; /* quot from using given u,v sizes */
|
|
rsize = prec + 1; /* desired quot */
|
|
|
|
zeros = rsize - prospective_rsize; /* padding u to give rsize */
|
|
copy_u = (zeros > 0 || rp == up); /* copy u if overlap or padding */
|
|
|
|
chop = MAX (-zeros, 0); /* negative zeros means shorten u */
|
|
up += chop;
|
|
usize -= chop;
|
|
zeros += chop; /* now zeros >= 0 */
|
|
|
|
tsize = usize + zeros; /* size for possible copy of u */
|
|
|
|
/* copy and possibly extend u if necessary */
|
|
if (copy_u)
|
|
{
|
|
tp = TMP_ALLOC_LIMBS (tsize + 1); /* +1 for mpn_div_q's scratch needs */
|
|
MPN_ZERO (tp, zeros);
|
|
MPN_COPY (tp+zeros, up, usize);
|
|
up = tp;
|
|
usize = tsize;
|
|
}
|
|
else
|
|
{
|
|
tp = TMP_ALLOC_LIMBS (usize + 1);
|
|
}
|
|
|
|
/* ensure divisor doesn't overlap quotient */
|
|
if (rp == vp)
|
|
{
|
|
new_vp = TMP_ALLOC_LIMBS (vsize);
|
|
MPN_COPY (new_vp, vp, vsize);
|
|
vp = new_vp;
|
|
}
|
|
|
|
ASSERT (usize-vsize+1 == rsize);
|
|
mpn_div_q (rp, up, usize, vp, vsize, tp);
|
|
|
|
/* strip possible zero high limb */
|
|
high_zero = (rp[rsize-1] == 0);
|
|
rsize -= high_zero;
|
|
rexp -= high_zero;
|
|
|
|
SIZ(r) = sign_quotient >= 0 ? rsize : -rsize;
|
|
EXP(r) = rexp;
|
|
TMP_FREE;
|
|
}
|