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[glibc.git] / sysdeps / libm-ieee754 / s_frexp.c
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1 /* @(#)s_frexp.c 5.1 93/09/24 */
2 /*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 * ====================================================
13 #if defined(LIBM_SCCS) && !defined(lint)
14 static char rcsid[] = "$NetBSD: s_frexp.c,v 1.9 1995/05/10 20:47:24 jtc Exp $";
15 #endif
18 * for non-zero x
19 * x = frexp(arg,&exp);
20 * return a double fp quantity x such that 0.5 <= |x| <1.0
21 * and the corresponding binary exponent "exp". That is
22 * arg = x*2^exp.
23 * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
24 * with *exp=0.
27 #include "math.h"
28 #include "math_private.h"
30 #ifdef __STDC__
31 static const double
32 #else
33 static double
34 #endif
35 two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
37 #ifdef __STDC__
38 double __frexp(double x, int *eptr)
39 #else
40 double __frexp(x, eptr)
41 double x; int *eptr;
42 #endif
44 int32_t hx, ix, lx;
45 EXTRACT_WORDS(hx,lx,x);
46 ix = 0x7fffffff&hx;
47 *eptr = 0;
48 if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */
49 if (ix<0x00100000) { /* subnormal */
50 x *= two54;
51 GET_HIGH_WORD(hx,x);
52 ix = hx&0x7fffffff;
53 *eptr = -54;
55 *eptr += (ix>>20)-1022;
56 hx = (hx&0x800fffff)|0x3fe00000;
57 SET_HIGH_WORD(x,hx);
58 return x;
60 weak_alias (__frexp, frexp)
61 #ifdef NO_LONG_DOUBLE
62 strong_alias (__frexp, __frexpl)
63 weak_alias (__frexp, frexpl)
64 #endif