mirror of
https://github.com/Relintai/sdl2_frt.git
synced 2024-12-20 22:16:49 +01:00
80 lines
2.3 KiB
C
80 lines
2.3 KiB
C
|
/* @(#)s_scalbn.c 5.1 93/09/24 */
|
||
|
|
/*
|
||
|
|
* ====================================================
|
||
|
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
||
|
|
*
|
||
|
|
* Developed at SunPro, a Sun Microsystems, Inc. business.
|
||
|
|
* Permission to use, copy, modify, and distribute this
|
||
|
|
* software is freely granted, provided that this notice
|
||
|
|
* is preserved.
|
||
|
|
* ====================================================
|
||
|
|
*/
|
||
|
|
|
||
|
|
#if defined(LIBM_SCCS) && !defined(lint)
|
||
|
|
static const char rcsid[] =
|
||
|
|
"$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $";
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/*
|
||
|
|
* scalbn (double x, int n)
|
||
|
|
* scalbn(x,n) returns x* 2**n computed by exponent
|
||
|
|
* manipulation rather than by actually performing an
|
||
|
|
* exponentiation or a multiplication.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include "math_libm.h"
|
||
|
|
#include "math_private.h"
|
||
|
|
|
||
|
|
libm_hidden_proto(copysign)
|
||
|
|
#ifdef __STDC__
|
||
|
|
static const double
|
||
|
|
#else
|
||
|
|
static double
|
||
|
|
#endif
|
||
|
|
two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
|
||
|
|
twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
|
||
|
|
huge_val = 1.0e+300, tiny = 1.0e-300;
|
||
|
|
|
||
|
|
libm_hidden_proto(scalbn)
|
||
|
|
#ifdef __STDC__
|
||
|
|
double scalbn(double x, int n)
|
||
|
|
#else
|
||
|
|
double scalbn(x, n)
|
||
|
|
double x;
|
||
|
|
int n;
|
||
|
|
#endif
|
||
|
|
{
|
||
|
|
int32_t k, hx, lx;
|
||
|
|
EXTRACT_WORDS(hx, lx, x);
|
||
|
|
k = (hx & 0x7ff00000) >> 20; /* extract exponent */
|
||
|
|
if (k == 0) { /* 0 or subnormal x */
|
||
|
|
if ((lx | (hx & 0x7fffffff)) == 0)
|
||
|
|
return x; /* +-0 */
|
||
|
|
x *= two54;
|
||
|
|
GET_HIGH_WORD(hx, x);
|
||
|
|
k = ((hx & 0x7ff00000) >> 20) - 54;
|
||
|
|
if (n < -50000)
|
||
|
|
return tiny * x; /* underflow */
|
||
|
|
}
|
||
|
|
if (k == 0x7ff)
|
||
|
|
return x + x; /* NaN or Inf */
|
||
|
|
k = k + n;
|
||
|
|
if (k > 0x7fe)
|
||
|
|
return huge_val * copysign(huge_val, x); /* overflow */
|
||
|
|
if (k > 0) { /* normal result */
|
||
|
|
SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
|
||
|
|
return x;
|
||
|
|
}
|
||
|
|
if (k <= -54) {
|
||
|
|
if (n > 50000) /* in case integer overflow in n+k */
|
||
|
|
return huge_val * copysign(huge_val, x); /* overflow */
|
||
|
|
else
|
||
|
|
return tiny * copysign(tiny, x); /* underflow */
|
||
|
|
}
|
||
|
|
k += 54; /* subnormal result */
|
||
|
|
SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
|
||
|
|
return x * twom54;
|
||
|
|
}
|
||
|
|
|
||
|
|
libm_hidden_def(scalbn)
|