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 __FBSDID("$FreeBSD$");
15
16 /*
17 * for non-zero x
18 * x = frexp(arg,&exp);
19 * return a double fp quantity x such that 0.5 <= |x| <1.0
20 * and the corresponding binary exponent "exp". That is
21 * arg = x*2^exp.
22 * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
23 * with *exp=0.
24 */
25
26 #include <float.h>
27
28 #include "math.h"
29 #include "math_private.h"
30
31 static const double
32 two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
33
34 double
frexp(double x,int * eptr)35 frexp(double x, int *eptr)
36 {
37 int32_t hx, ix, lx;
38 EXTRACT_WORDS(hx,lx,x);
39 ix = 0x7fffffff&hx;
40 *eptr = 0;
41 if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */
42 if (ix<0x00100000) { /* subnormal */
43 x *= two54;
44 GET_HIGH_WORD(hx,x);
45 ix = hx&0x7fffffff;
46 *eptr = -54;
47 }
48 *eptr += (ix>>20)-1022;
49 hx = (hx&0x800fffff)|0x3fe00000;
50 SET_HIGH_WORD(x,hx);
51 return x;
52 }
53
54 #if (LDBL_MANT_DIG == 53)
55 __weak_reference(frexp, frexpl);
56 #endif
57