1 /*
2 * The authors of this software are Rob Pike and Ken Thompson,
3 * with contributions from Mike Burrows and Sean Dorward.
4 *
5 * Copyright (c) 2002-2006 by Lucent Technologies.
6 * Portions Copyright (c) 2004 Google Inc.
7 *
8 * Permission to use, copy, modify, and distribute this software for any
9 * purpose without fee is hereby granted, provided that this entire notice
10 * is included in all copies of any software which is or includes a copy
11 * or modification of this software and in all copies of the supporting
12 * documentation for such software.
13 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
14 * WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES
15 * NOR GOOGLE INC MAKE ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING
16 * THE MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
17 */
18
19 /*
20 * 64-bit IEEE not-a-number routines.
21 * This is big/little-endian portable assuming that
22 * the 64-bit doubles and 64-bit integers have the
23 * same byte ordering.
24 */
25
26 #include <u.h>
27 #include <libc.h>
28 #include "fmtdef.h"
29
30 static uvlong uvnan = ((uvlong)0x7FF00000<<32)|0x00000001;
31 static uvlong uvinf = ((uvlong)0x7FF00000<<32)|0x00000000;
32 static uvlong uvneginf = ((uvlong)0xFFF00000<<32)|0x00000000;
33
34 /* gcc sees through the obvious casts. */
35 static uvlong
36 d2u(double d)
37 {
38 union {
39 uvlong v;
40 double d;
41 } u;
42 assert(sizeof(u.d) == sizeof(u.v));
43 u.d = d;
44 return u.v;
45 }
46
47 static double
48 u2d(uvlong v)
49 {
50 union {
51 uvlong v;
52 double d;
53 } u;
54 assert(sizeof(u.d) == sizeof(u.v));
55 u.v = v;
56 return u.d;
57 }
58
59 double
60 __NaN(void)
61 {
62 return u2d(uvnan);
63 }
64
65 int
66 __isNaN(double d)
67 {
68 uvlong x;
69
70 x = d2u(d);
71 /* IEEE 754: exponent bits 0x7FF and non-zero mantissa */
72 return (x&uvinf) == uvinf && (x&~uvneginf) != 0;
73 }
74
75 double
76 __Inf(int sign)
77 {
78 return u2d(sign < 0 ? uvneginf : uvinf);
79 }
80
81 int
82 __isInf(double d, int sign)
83 {
84 uvlong x;
85
86 x = d2u(d);
87 if(sign == 0)
88 return x==uvinf || x==uvneginf;
89 else if(sign > 0)
90 return x==uvinf;
91 else
92 return x==uvneginf;
93 }