frexpd32.c

/* Break dfp number into normalized fraction and integral power of two

   Copyright (C) 2006 IBM Corporation.
   Copyright (C) 2007-2015 Free Software Foundation, Inc.

   This file is part of the Decimal Floating Point C Library.

   Author(s): Joseph Kerian <jkerian@us.ibm.com>

   The Decimal Floating Point C Library is free software; you can
   redistribute it and/or modify it under the terms of the GNU Lesser
   General Public License version 2.1.

   The Decimal Floating Point C 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 version 2.1 for more details.

   You should have received a copy of the GNU Lesser General Public
   License version 2.1 along with the Decimal Floating Point C Library;
   if not, write to the Free Software Foundation, Inc., 51 Franklin
   Street, Fifth Floor, Boston, MA 02110-1301 USA.

   Please see libdfp/COPYING.txt for more information.  */

#ifndef _DECIMAL_SIZE
#  define _DECIMAL_SIZE 32
#  include <decimal32.h>
#endif

#include <decContext.h>
#include <decNumber.h>
#include <math.h>
#include <ieee754r_private.h>

#include <decNumberMath.h>

#define FUNCTION_NAME frexp

#include <dfpmacro.h>
#include <numdigits.h>

DEC_TYPE
INTERNAL_FUNCTION_NAME (DEC_TYPE x, int *y)
{
  /* GCC isn't smart enough to realize that the else block sets this in the
   * FUNC_CONVERT_FROM_DN macro so simply initialize it to NaN to silence the
   * warnings.  */
  DEC_TYPE result = DEC_NAN;

#if NUMDIGITS_SUPPORT==1
  int digits, exponent;

  if (FUNC_D (__isinf) (x) || FUNC_D (__isnan) (x))
    return x+x;

  // Given 3.1e0 is encoded as 31e-1 and we want .31e1
  // We have 2 'digits'.

  // Given 30.0e0 is encoded as 300e-1 and we want .300e2
  // We have 3 'digits'.

  // Given .003e0 is encoded as 3e3 and we want .3e-2
  // We have 1 'digits'.

  digits = FUNC_D (numdigits) (x);

  // We have -1 exponent.

  // We have -1 exponent.

  // We have -3 exponent.

  exponent = FUNC_D (getexp) (x);
  *y = digits + exponent;

  result = FUNC_D(setexp) (x, -digits);
  //2 + (-1) = 1   0

  //3 + (-1) = 2   0

  //1 + (-3) = -2

#else
  decNumber dn_x;
  decContext context;

  *y = 0;
  FUNC_CONVERT_TO_DN(&x, &dn_x);
  if (___decNumberIsNaN (&dn_x) || ___decNumberIsInfinite (&dn_x)
	|| ___decNumberIsZero (&dn_x))
    return x+x;

  *y = dn_x.digits + dn_x.exponent;
  dn_x.exponent = -dn_x.digits;

  decContextDefault(&context, DEFAULT_CONTEXT);
  FUNC_CONVERT_FROM_DN (&dn_x, &result, &context);
#endif 

  return result;
}

weak_alias (INTERNAL_FUNCTION_NAME, EXTERNAL_FUNCTION_NAME)