/* mpfr_cmpabs -- compare the absolute values of two FP numbers

Copyright 1999, 2001, 2002, 2003, 2004, 2006, 2007, 2008 Free Software Foundation, Inc.
Contributed by the Arenaire and Cacao projects, INRIA.

This file is part of the MPFR Library.

The MPFR 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 2.1 of the License, or (at your
option) any later version.

The MPFR 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 MPFR Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
MA 02110-1301, USA. */

#include "mpfr-impl.h"

/* Return a positive value if abs(b) > abs(c), 0 if abs(b) = abs(c), and
   a negative value if abs(b) < abs(c). Neither b nor c may be NaN. */

int
mpfr_cmpabs (mpfr_srcptr b, mpfr_srcptr c)
{
  mp_exp_t be, ce;
  mp_size_t bn, cn;
  mp_limb_t *bp, *cp;

  if (MPFR_ARE_SINGULAR (b, c))
    {
      if (MPFR_IS_NAN (b) || MPFR_IS_NAN (c))
        {
          MPFR_SET_ERANGE ();
          return 0;
        }
      else if (MPFR_IS_INF (b))
        return ! MPFR_IS_INF (c);
      else if (MPFR_IS_INF (c))
        return -1;
      else if (MPFR_IS_ZERO (c))
        return ! MPFR_IS_ZERO (b);
      else /* b == 0 */
        return -1;
    }

  MPFR_ASSERTD (MPFR_IS_PURE_FP (b));
  MPFR_ASSERTD (MPFR_IS_PURE_FP (c));

  /* Now that we know that b and c are pure FP numbers (i.e. they have
     a meaningful exponent), we use MPFR_EXP instead of MPFR_GET_EXP to
     allow exponents outside the current exponent range. For instance,
     this is useful for mpfr_pow, which compares values to __gmpfr_one.
     This is for internal use only! For compatibility with other MPFR
     versions, the user must still provide values that are representable
     in the current exponent range. */
  be = MPFR_EXP (b);
  ce = MPFR_EXP (c);
  if (be > ce)
    return 1;
  if (be < ce)
    return -1;

  /* exponents are equal */

  bn = MPFR_LIMB_SIZE(b)-1;
  cn = MPFR_LIMB_SIZE(c)-1;

  bp = MPFR_MANT(b);
  cp = MPFR_MANT(c);

  for ( ; bn >= 0 && cn >= 0; bn--, cn--)
    {
      if (bp[bn] > cp[cn])
        return 1;
      if (bp[bn] < cp[cn])
        return -1;
    }

  for ( ; bn >= 0; bn--)
    if (bp[bn])
      return 1;

  for ( ; cn >= 0; cn--)
    if (cp[cn])
      return -1;

   return 0;
}
