Blame view

RIOT/sys/quad_math/floatdisf.c 2.61 KB
a752c7ab   elopes   add first test an...
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
  /* $OpenBSD: floatdisf.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 float.
   */
  float __floatdisf(quad_t x)
  {
      float f;
      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 f, 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.
       *
       * Using double here may be excessive paranoia.
       */
      f = (double) u.ul[H] * (((int) 1 << (INT_BITS - 2)) * 4.0);
      f += u.ul[L];
  
      return neg ? -f : f;
  }