lib/libc/quad/floatdidf.c

   1 /*      $NetBSD: floatdidf.c,v 1.5 2002/10/20 10:15:47 scw Exp $        */
   2
   3 /*-
   4  * Copyright (c) 1992, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This software was developed by the Computer Systems Engineering group
   8  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
   9  * contributed to Berkeley.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 #include <sys/cdefs.h>
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 #if 0
  39 static char sccsid[] = "@(#)floatdidf.c 8.1 (Berkeley) 6/4/93";
  40 #else
  41 __RCSID("$NetBSD: floatdidf.c,v 1.5 2002/10/20 10:15:47 scw Exp $");
  42 #endif
  43 #endif /* LIBC_SCCS and not lint */
  44
  45 #include "quad.h"
  46
  47 /*
  48  * Convert (signed) quad to double.
  49  */
  50 double
  51 __floatdidf(x)
  52         quad_t x;
  53 {
  54         double d;
  55         union uu u;
  56         int neg;
  57
  58         /*
  59          * Get an unsigned number first, by negating if necessary.
  60          */
  61         if (x < 0)
  62                 u.q = -x, neg = 1;
  63         else
  64                 u.q = x, neg = 0;
  65
  66         /*
  67          * Now u.ul[H] has the factor of 2^32 (or whatever) and u.ul[L]
  68          * has the units.  Ideally we could just set d, add INT_BITS to
  69          * its exponent, and then add the units, but this is portable
  70          * code and does not know how to get at an exponent.  Machine-
  71          * specific code may be able to do this more efficiently.
  72          */
  73         d = (double)u.ul[H] * (((int)1 << (INT_BITS - 2)) * 4.0);
  74         d += u.ul[L];
  75
  76         return (neg ? -d : d);
  77 }