1 /* Copyright (c) 2002-2006 Lucent Technologies; see LICENSE */
2 
3 /*
4  * 64-bit IEEE not-a-number routines.
5  * This is big/little-endian portable assuming that
6  * the 64-bit doubles and 64-bit integers have the
7  * same byte ordering.
8  */
9 
10 #include "plan9.h"
11 #include <assert.h>
12 #include "fmt.h"
13 #include "fmtdef.h"
14 
15 static uvlong uvnan    = ((uvlong)0x7FF00000<<32)|0x00000001;
16 static uvlong uvinf    = ((uvlong)0x7FF00000<<32)|0x00000000;
17 static uvlong uvneginf = ((uvlong)0xFFF00000<<32)|0x00000000;
18 
19 /* gcc sees through the obvious casts. */
20 static uvlong
21 d2u(double d)
22 {
23 	union {
24 		uvlong v;
25 		double d;
26 	} u;
27 	assert(sizeof(u.d) == sizeof(u.v));
28 	u.d = d;
29 	return u.v;
30 }
31 
32 static double
33 u2d(uvlong v)
34 {
35 	union {
36 		uvlong v;
37 		double d;
38 	} u;
39 	assert(sizeof(u.d) == sizeof(u.v));
40 	u.v = v;
41 	return u.d;
42 }
43 
44 double
45 __NaN(void)
46 {
47 	return u2d(uvnan);
48 }
49 
50 int
51 __isNaN(double d)
52 {
53 	uvlong x;
54 
55 	x = d2u(d);
56 	/* IEEE 754: exponent bits 0x7FF and non-zero mantissa */
57 	return (x&uvinf) == uvinf && (x&~uvneginf) != 0;
58 }
59 
60 double
61 __Inf(int sign)
62 {
63 	return u2d(sign < 0 ? uvneginf : uvinf);
64 }
65 
66 int
67 __isInf(double d, int sign)
68 {
69 	uvlong x;
70 
71 	x = d2u(d);
72 	if(sign == 0)
73 		return x==uvinf || x==uvneginf;
74 	else if(sign > 0)
75 		return x==uvinf;
76 	else
77 		return x==uvneginf;
78 }