lib/libc/quad/floatdisf.c

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