1 /*
2  * Copyright (c) 1998, 2001, Oracle and/or its affiliates. All rights reserved.
3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4  *
5  * This code is free software; you can redistribute it and/or modify it
6  * under the terms of the GNU General Public License version 2 only, as
7  * published by the Free Software Foundation.  Oracle designates this
8  * particular file as subject to the "Classpath" exception as provided
9  * by Oracle in the LICENSE file that accompanied this code.
10  *
11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
18  * 2 along with this work; if not, write to the Free Software Foundation,
19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20  *
21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22  * or visit www.oracle.com if you need additional information or have any
23  * questions.
24  */
25 
26 /*
27  * for non-zero x
28  *      x = frexp(arg,&exp);
29  * return a double fp quantity x such that 0.5 <= |x| <1.0
30  * and the corresponding binary exponent "exp". That is
31  *      arg = x*2^exp.
32  * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
33  * with *exp=0.
34  */
35 
36 #include "fdlibm.h"
37 
38 #ifdef __STDC__
39 static const double
40 #else
41 static double
42 #endif
43 two54 =  1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
44 
45 #ifdef __STDC__
frexp(double x,int * eptr)46         double frexp(double x, int *eptr)
47 #else
48         double frexp(x, eptr)
49         double x; int *eptr;
50 #endif
51 {
52         int  hx, ix, lx;
53         hx = __HI(x);
54         ix = 0x7fffffff&hx;
55         lx = __LO(x);
56         *eptr = 0;
57         if(ix>=0x7ff00000||((ix|lx)==0)) return x;      /* 0,inf,nan */
58         if (ix<0x00100000) {            /* subnormal */
59             x *= two54;
60             hx = __HI(x);
61             ix = hx&0x7fffffff;
62             *eptr = -54;
63         }
64         *eptr += (ix>>20)-1022;
65         hx = (hx&0x800fffff)|0x3fe00000;
66         __HI(x) = hx;
67         return x;
68 }
69