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	nan64.c - 9base - revived minimalist port of Plan 9 userland to Unix
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	---
	nan64.c (1196B)
	---
	1 /*
	2 * 64-bit IEEE not-a-number routines.
	3 * This is big/little-endian portable assuming that
	4 * the 64-bit doubles and 64-bit integers have the
	5 * same byte ordering.
	6 */
	7
	8 #include "plan9.h"
	9 #include <assert.h>
	10 #include "fmt.h"
	11 #include "fmtdef.h"
	12
	13 static uvlong uvnan = ((uvlong)0x7FF00000<<32)\|0x00000001;
	14 static uvlong uvinf = ((uvlong)0x7FF00000<<32)\|0x00000000;
	15 static uvlong uvneginf = ((uvlong)0xFFF00000<<32)\|0x00000000;
	16
	17 /* gcc sees through the obvious casts. */
	18 static uvlong
	19 d2u(double d)
	20 {
	21 union {
	22 uvlong v;
	23 double d;
	24 } u;
	25 assert(sizeof(u.d) == sizeof(u.v));
	26 u.d = d;
	27 return u.v;
	28 }
	29
	30 static double
	31 u2d(uvlong v)
	32 {
	33 union {
	34 uvlong v;
	35 double d;
	36 } u;
	37 assert(sizeof(u.d) == sizeof(u.v));
	38 u.v = v;
	39 return u.d;
	40 }
	41
	42 double
	43 __NaN(void)
	44 {
	45 return u2d(uvnan);
	46 }
	47
	48 int
	49 __isNaN(double d)
	50 {
	51 uvlong x;
	52
	53 x = d2u(d);
	54 /* IEEE 754: exponent bits 0x7FF and non-zero mantissa */
	55 return (x&uvinf) == uvinf && (x&~uvneginf) != 0;
	56 }
	57
	58 double
	59 __Inf(int sign)
	60 {
	61 return u2d(sign < 0 ? uvneginf : uvinf);
	62 }
	63
	64 int
	65 __isInf(double d, int sign)
	66 {
	67 uvlong x;
	68
	69 x = d2u(d);
	70 if(sign == 0)
	71 return x==uvinf \|\| x==uvneginf;
	72 else if(sign > 0)
	73 return x==uvinf;
	74 else
	75 return x==uvneginf;
	76 }