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/* Nelper routines to convert from integer to real.

   Copyright 2004, 2005 Free Software Foundation, Inc.

   Contributed by Paul Brook.

This file is part of the GNU Fortran 95 runtime library (libgfortran).

Libgfortran is free software; you can redistribute it and/or

modify it under the terms of 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.

In addition to the permissions in the GNU General Public License, the

Free Software Foundation gives you unlimited permission to link the

compiled version of this file into combinations with other programs,

and to distribute those combinations without any restriction coming

from the use of this file.  (The General Public License restrictions

do apply in other respects; for example, they cover modification of

the file, and distribution when not linked into a combine

executable.)

Ligbfortran 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 a copy of the GNU General Public

License along with libgfortran; see the file COPYING.  If not,

write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,

Boston, MA 02110-1301, USA.  */

#include <math.h>

#include "libgfortran.h"

/* These routines can be sensitive to excess precision, so should really be

   compiled with -ffloat-store.  */

/* Return the largest value less than one representable in a REAL*4.  */

static inline GFC_REAL_4

almostone_r4 (void)

{

#ifdef HAVE_NEXTAFTERF

  return nextafterf (1.0f, 0.0f);

#else

  /* The volatile is a hack to prevent excess precision on x86.  */

  static volatile GFC_REAL_4 val = 0.0f;

  GFC_REAL_4 x;

  if (val != 0.0f)

    return val;

  val = 0.9999f;

  do

    {

      x = val;

      val = (val + 1.0f) / 2.0f;

    }

  while (val > x && val < 1.0f);

  if (val == 1.0f)

    val = x;

  return val;

#endif

}

/* Return the largest value less than one representable in a REAL*8.  */

static inline GFC_REAL_8

almostone_r8 (void)

{

#ifdef HAVE_NEXTAFTER

  return nextafter (1.0, 0.0);

#else

  static volatile GFC_REAL_8 val = 0.0;

  GFC_REAL_8 x;

  if (val != 0.0)

    return val;

  val = 0.9999;

  do

    {

      x = val;

      val = (val + 1.0) / 2.0;

    }

  while (val > x && val < 1.0);

  if (val == 1.0)

    val = x;

  return val;

#endif

}

/* Convert an unsigned integer in the range [0..x] into a

   real the range [0..1).  */

GFC_REAL_4

normalize_r4_i4 (GFC_UINTEGER_4 i, GFC_UINTEGER_4 x)

{

  GFC_REAL_4 r;

  r = (GFC_REAL_4) i / (GFC_REAL_4) x;

  if (r == 1.0f)

    r = almostone_r4 ();

  return r;

}

/* Convert an unsigned integer in the range [0..x] into a

   real the range [0..1).  */

GFC_REAL_8

normalize_r8_i8 (GFC_UINTEGER_8 i, GFC_UINTEGER_8 x)

{

  GFC_REAL_8 r;

  r = (GFC_REAL_8) i / (GFC_REAL_8) x;

  if (r == 1.0)

    r = almostone_r8 ();

  return r;

}