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RIOT/sys/quad_math/floatdidf.c 2.55 KB
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  /* $OpenBSD: floatdidf.c,v 1.6 2005/08/08 08:05:35 espie Exp $ */
  /*-
   * Copyright (c) 1992, 1993
   * The Regents of the University of California.  All rights reserved.
   *
   * This software was developed by the Computer Systems Engineering group
   * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
   * contributed to Berkeley.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  
  #include "quad.h"
  
  /*
   * Convert (signed) quad to double.
   */
  double __floatdidf(quad_t x)
  {
      double d;
      union uu u;
      int neg;
  
      /*
       * Get an unsigned number first, by negating if necessary.
       */
      if (x < 0) {
          u.q = -x;
          neg = 1;
      }
      else {
          u.q = x;
          neg = 0;
      }
  
      /*
       * Now u.ul[H] has the factor of 2^32 (or whatever) and u.ul[L]
       * has the units.  Ideally we could just set d, add INT_BITS to
       * its exponent, and then add the units, but this is portable
       * code and does not know how to get at an exponent.  Machine-
       * specific code may be able to do this more efficiently.
       */
      d = (double) u.ul[H] * (((int) 1 << (INT_BITS - 2)) * 4.0);
      d += u.ul[L];
  
      return neg ? -d : d;
  }