1 
2 /* @(#)s_frexp.c 1.4 95/01/18 */
3 /*
4  * ====================================================
5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6  *
7  * Developed at SunSoft, a Sun Microsystems, Inc. business.
8  * Permission to use, copy, modify, and distribute this
9  * software is freely granted, provided that this notice
10  * is preserved.
11  * ====================================================
12  */
13 
14 /*
15  * for non-zero x
16  *	x = ieee_frexp(arg,&exp);
17  * return a double fp quantity x such that 0.5 <= |x| <1.0
18  * and the corresponding binary exponent "exp". That is
19  *	arg = x*2^exp.
20  * If arg is inf, 0.0, or NaN, then ieee_frexp(arg,&exp) returns arg
21  * with *exp=0.
22  */
23 
24 #include "fdlibm.h"
25 
26 #ifdef __STDC__
27 static const double
28 #else
29 static double
30 #endif
31 two54 =  1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
32 
33 #ifdef __STDC__
ieee_frexp(double x,int * eptr)34 	double ieee_frexp(double x, int *eptr)
35 #else
36 	double ieee_frexp(x, eptr)
37 	double x; int *eptr;
38 #endif
39 {
40 	int  hx, ix, lx;
41 	hx = __HI(x);
42 	ix = 0x7fffffff&hx;
43 	lx = __LO(x);
44 	*eptr = 0;
45 	if(ix>=0x7ff00000||((ix|lx)==0)) return x;	/* 0,inf,nan */
46 	if (ix<0x00100000) {		/* subnormal */
47 	    x *= two54;
48 	    hx = __HI(x);
49 	    ix = hx&0x7fffffff;
50 	    *eptr = -54;
51 	}
52 	*eptr += (ix>>20)-1022;
53 	hx = (hx&0x800fffff)|0x3fe00000;
54 	__HI(x) = hx;
55 	return x;
56 }
57