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ilogbd32.c

/* Returns the unbiased exponent of the passed _Decimal32 value as an int

   Copyright (C) 2006 IBM Corporation.
   Copyright (C) 2007, 2009 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., 59 Temple Place,
   Suite 330, Boston, MA 02111-1307 USA.

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

#ifndef _DECIMAL_SIZE
#  include <decimal32.h>
#  define _DECIMAL_SIZE 32
#  define DFP_DEBUG(arg) printf("%Hf\n", arg)
#endif

#include <decContext.h>
#include <decNumber.h>
#include <math.h>
#include <limits.h>
#include <errno.h>

#include <decNumberMath.h>

#define FUNCTION_NAME ilogb

#include <dfpmacro.h>

static int
IEEE_FUNCTION_NAME (DEC_TYPE x)
{
  DEC_TYPE result;
  decContext context;
  decNumber dn_result;
  decNumber dn_x;
  decNumber dn_absx;
  decNumber dn_logx;
 /* int i_result; */

  FUNC_CONVERT_TO_DN(&x, &dn_x);
  if (___decNumberIsZero (&dn_x))
    {
      DFP_EXCEPT (FE_INVALID);
      return FP_ILOGB0;
    }
  if (___decNumberIsInfinite (&dn_x))
    {
      DFP_EXCEPT (FE_INVALID);
      return INT_MAX;
    }
  if (___decNumberIsNaN (&dn_x))
    {
      DFP_EXCEPT (FE_INVALID);
      return FP_ILOGBNAN;
    }

  ___decContextDefault(&context, DEFAULT_CONTEXT);

  ___decNumberAbs(&dn_absx, &dn_x, &context);

  /*  For DFP, we use radix 10 instead of whatever FLT_RADIX
      happens to be */
  ___decNumberLog10(&dn_logx, &dn_absx, &context);

  /* Capture the case where truncation will return the wrong result.  */
  if (x < DFP_CONSTANT(1.0) && x > DFP_CONSTANT(-1.0))
    context.round = DEC_ROUND_UP; /* round away from zero  */
  else
    context.round = DEC_ROUND_DOWN; /*  truncate */
  ___decNumberToIntegralValue(&dn_result, &dn_logx, &context);

  FUNC_CONVERT_FROM_DN(&dn_result, &result, &context);
  /* Use _Decimal* to int casting.  */
  return (int)result;
}

int
INTERNAL_FUNCTION_NAME (DEC_TYPE x)
{
  int z = IEEE_FUNCTION_NAME (x);
#ifndef _IEEE_LIBDFP
  if(_LIB_VERSION == _IEEE_) return z;
  if(x == DFP_CONSTANT(0.0) || isinf(x) || isnan(x) ||
            x > INT_MAX || x < INT_MIN)
        DFP_ERRNO(EDOM);
#endif
  return z;
}

weak_alias (INTERNAL_FUNCTION_NAME, EXTERNAL_FUNCTION_NAME)

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