1#include "SDL_internal.h"
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/*
14 * scalbln(double x, long n)
15 * scalbln(x,n) returns x * 2**n computed by exponent
16 * manipulation rather than by actually performing an
17 * exponentiation or a multiplication.
18 */
19
20#include "math_libm.h"
21#include "math_private.h"
22#include <limits.h>
23
24#ifdef __WATCOMC__ /* Watcom defines huge=__huge */
25#undef huge
26#endif
27
28static const double
29two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
30twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
31huge = 1.0e+300,
32tiny = 1.0e-300;
33
34double scalbln(double x, long n)
35{
36 int32_t k, hx, lx;
37
38 EXTRACT_WORDS(hx, lx, x);
39 k = (hx & 0x7ff00000) >> 20; /* extract exponent */
40 if (k == 0) { /* 0 or subnormal x */
41 if ((lx | (hx & 0x7fffffff)) == 0)
42 return x; /* +-0 */
43 x *= two54;
44 GET_HIGH_WORD(hx, x);
45 k = ((hx & 0x7ff00000) >> 20) - 54;
46 }
47 if (k == 0x7ff)
48 return x + x; /* NaN or Inf */
49 k = (int32_t)(k + n);
50 if (k > 0x7fe)
51 return huge * copysign(huge, x); /* overflow */
52 if (n < -50000)
53 return tiny * copysign(tiny, x); /* underflow */
54 if (k > 0) { /* normal result */
55 SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
56 return x;
57 }
58 if (k <= -54) {
59 if (n > 50000) /* in case integer overflow in n+k */
60 return huge * copysign(huge, x); /* overflow */
61 return tiny * copysign(tiny, x); /* underflow */
62 }
63 k += 54; /* subnormal result */
64 SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
65 return x * twom54;
66}
67libm_hidden_def(scalbln)
68
69
70double scalbn(double x, int n)
71{
72 return scalbln(x, n);
73}
74libm_hidden_def(scalbn)
75