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sp_modf.c

/* IEEE754 floating point arithmetic
 * single precision
 */
/*
 * MIPS floating point support
 * Copyright (C) 1994-2000 Algorithmics Ltd.
 * http://www.algor.co.uk
 *
 * ########################################################################
 *
 *  This program is free software; you can distribute it and/or modify it
 *  under the terms of the GNU General Public License (Version 2) as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope 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 this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * ########################################################################
 */


#include "ieee754sp.h"

/* modf function is always exact for a finite number
*/
ieee754sp ieee754sp_modf(ieee754sp x, ieee754sp * ip)
{
      COMPXSP;

      CLEARCX;

      EXPLODEXSP;

      switch (xc) {
      case IEEE754_CLASS_SNAN:
      case IEEE754_CLASS_QNAN:
      case IEEE754_CLASS_INF:
      case IEEE754_CLASS_ZERO:
            *ip = x;
            return x;
      case IEEE754_CLASS_DNORM:
            /* far to small */
            *ip = ieee754sp_zero(xs);
            return x;
      case IEEE754_CLASS_NORM:
            break;
      }
      if (xe < 0) {
            *ip = ieee754sp_zero(xs);
            return x;
      }
      if (xe >= SP_MBITS) {
            *ip = x;
            return ieee754sp_zero(xs);
      }
      /* generate ipart mantissa by clearing bottom bits
       */
      *ip = buildsp(xs, xe + SP_EBIAS,
                  ((xm >> (SP_MBITS - xe)) << (SP_MBITS - xe)) &
                  ~SP_HIDDEN_BIT);

      /* generate fpart mantissa by clearing top bits
       * and normalizing (must be able to normalize)
       */
      xm = (xm << (32 - (SP_MBITS - xe))) >> (32 - (SP_MBITS - xe));
      if (xm == 0)
            return ieee754sp_zero(xs);

      while ((xm >> SP_MBITS) == 0) {
            xm <<= 1;
            xe--;
      }
      return buildsp(xs, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT);
}

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