1 /* @(#)s_frexp.c 5.1 93/09/24 */
2 /*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13 #include <sys/cdefs.h>
14 #if defined(LIBM_SCCS) && !defined(lint)
15 __RCSID("$NetBSD: s_frexp.c,v 1.14 2020/01/30 20:31:50 joerg Exp $");
16 #endif
17
18 /*
19 * for non-zero x
20 * x = frexp(arg,&exp);
21 * return a double fp quantity x such that 0.5 <= |x| <1.0
22 * and the corresponding binary exponent "exp". That is
23 * arg = x*2^exp.
24 * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
25 * with *exp=0.
26 */
27
28 #include "math.h"
29 #include "math_private.h"
30
31 #ifndef __HAVE_LONG_DOUBLE
32 __strong_alias(frexpl, frexp)
33 #endif
34
35 static const double
36 two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
37
38 double
frexp(double x,int * eptr)39 frexp(double x, int *eptr)
40 {
41 int32_t hx, ix, lx;
42 EXTRACT_WORDS(hx,lx,x);
43 ix = 0x7fffffff&hx;
44 *eptr = 0;
45 if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */
46 if (ix<0x00100000) { /* subnormal */
47 x *= two54;
48 GET_HIGH_WORD(hx,x);
49 ix = hx&0x7fffffff;
50 *eptr = -54;
51 }
52 *eptr += ((uint32_t)ix>>20)-1022;
53 hx = (hx&0x800fffff)|0x3fe00000;
54 SET_HIGH_WORD(x,hx);
55 return x;
56 }
57