/* mpf_div -- Divide two floats.

Copyright 1993, 1994, 1996, 2000-2002, 2004, 2005, 2010, 2012 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 either:

  * 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.

or

  * the GNU General Public License as published by the Free Software

    Foundation; either version 2 of the License, or (at your option) any

    later version.

or both in parallel, as here.

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 copies of the GNU General Public License and the

GNU Lesser General Public License along with the GNU MP Library.  If not,

see https://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_div_q, 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);

  if (UNLIKELY (vsize == 0))

    DIVIDE_BY_ZERO;

  if (usize == 0)

    {

      SIZ(r) = 0;

      EXP(r) = 0;

      return;

    }

  sign_quotient = usize ^ vsize;

  usize = ABS (usize);

  vsize = ABS (vsize);

  prec = PREC(r);

  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;

}