1/*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 */
11
12/*
13 * scalbln(double x, long n)
14 * scalbln(x,n) returns x * 2**n computed by exponent
15 * manipulation rather than by actually performing an
16 * exponentiation or a multiplication.
17 */
18
19#include "math_libm.h"
20#include "math_private.h"
21#include <limits.h>
22
23#ifdef __WATCOMC__ /* Watcom defines huge=__huge */
24#undef huge
25#endif
26
27static const double
28two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
29twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
30huge = 1.0e+300,
31tiny = 1.0e-300;
32
33double scalbln(double x, long n)
34{
35 int32_t k, hx, lx;
36
37 EXTRACT_WORDS(hx, lx, x);
38 k = (hx & 0x7ff00000) >> 20; /* extract exponent */
39 if (k == 0) { /* 0 or subnormal x */
40 if ((lx | (hx & 0x7fffffff)) == 0)
41 return x; /* +-0 */
42 x *= two54;
43 GET_HIGH_WORD(hx, x);
44 k = ((hx & 0x7ff00000) >> 20) - 54;
45 }
46 if (k == 0x7ff)
47 return x + x; /* NaN or Inf */
48 k = (int32_t)(k + n);
49 if (k > 0x7fe)
50 return huge * copysign(huge, x); /* overflow */
51 if (n < -50000)
52 return tiny * copysign(tiny, x); /* underflow */
53 if (k > 0) { /* normal result */
54 SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
55 return x;
56 }
57 if (k <= -54) {
58 if (n > 50000) /* in case integer overflow in n+k */
59 return huge * copysign(huge, x); /* overflow */
60 return tiny * copysign(tiny, x); /* underflow */
61 }
62 k += 54; /* subnormal result */
63 SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
64 return x * twom54;
65}
66libm_hidden_def(scalbln)
67
68
69double scalbn(double x, int n)
70{
71 return scalbln(x, n);
72}
73libm_hidden_def(scalbn)
74