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 * scalbn (double x, int n)
28 * scalbn(x,n) returns x* 2**n computed by exponent
29 * manipulation rather than by actually performing an
30 * exponentiation or a multiplication.
31 */
32
33#include "fdlibm.h"
34
35#ifdef __STDC__
36static const double
37#else
38static double
39#endif
40two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
41twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
42huge = 1.0e+300,
43tiny = 1.0e-300;
44
45#ifdef __STDC__
46 double scalbn (double x, int n)
47#else
48 double scalbn (x,n)
49 double x; int n;
50#endif
51{
52 int k,hx,lx;
53 hx = __HI(x);
54 lx = __LO(x);
55 k = (hx&0x7ff00000)>>20; /* extract exponent */
56 if (k==0) { /* 0 or subnormal x */
57 if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
58 x *= two54;
59 hx = __HI(x);
60 k = ((hx&0x7ff00000)>>20) - 54;
61 if (n< -50000) return tiny*x; /*underflow*/
62 }
63 if (k==0x7ff) return x+x; /* NaN or Inf */
64 k = k+n;
65 if (k > 0x7fe) return huge*copysign(huge,x); /* overflow */
66 if (k > 0) /* normal result */
67 {__HI(x) = (hx&0x800fffff)|(k<<20); return x;}
68 if (k <= -54) {
69 if (n > 50000) /* in case integer overflow in n+k */
70 return huge*copysign(huge,x); /*overflow*/
71 else return tiny*copysign(tiny,x); /*underflow*/
72 }
73 k += 54; /* subnormal result */
74 __HI(x) = (hx&0x800fffff)|(k<<20);
75 return x*twom54;
76}
77