Atlas - s_scalbn.c
Home / ext / SDL / src / libm
Lines: 1 | Size: 1863 bytes
[Download] [Show on GitHub] [Search similar files] [Raw] [Raw (proxy)] 
[FILE BEGIN]
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
24static const double
25two54  = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
26twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
27huge   = 1.0e+300,
28tiny   = 1.0e-300;
29
30double scalbln(double x, long n)
31{
32	int32_t k, hx, lx;
33
34	EXTRACT_WORDS(hx, lx, x);
35	k = (hx & 0x7ff00000) >> 20; /* extract exponent */
36	if (k == 0) { /* 0 or subnormal x */
37		if ((lx | (hx & 0x7fffffff)) == 0)
38			return x; /* +-0 */
39		x *= two54;
40		GET_HIGH_WORD(hx, x);
41		k = ((hx & 0x7ff00000) >> 20) - 54;
42	}
43	if (k == 0x7ff)
44		return x + x; /* NaN or Inf */
45	k = (int32_t)(k + n);
46	if (k > 0x7fe)
47		return huge * copysign(huge, x); /* overflow */
48	if (n < -50000)
49		return tiny * copysign(tiny, x); /* underflow */
50	if (k > 0) { /* normal result */
51		SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
52		return x;
53	}
54	if (k <= -54) {
55		if (n > 50000) /* in case integer overflow in n+k */
56			return huge * copysign(huge, x); /* overflow */
57		return tiny * copysign(tiny, x); /* underflow */
58	}
59	k += 54; /* subnormal result */
60	SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
61	return x * twom54;
62}
63libm_hidden_def(scalbln)
64
65
66double scalbn(double x, int n)
67{
68	return scalbln(x, n);
69}
70libm_hidden_def(scalbn)
71
[FILE END]
(C) 2025 0x4248
(C) 2025 4248 Media and 4248 Systems, All part of 0x4248
See LICENCE files for more information. Not all files are by 0x4248 always check Licencing.