mirror of
https://github.com/KolibriOS/kolibrios.git
synced 2024-12-22 06:43:28 +03:00
111 lines
2.8 KiB
C
111 lines
2.8 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.
|
||
|
|
* ====================================================
|
||
|
|
*/
|
||
|
|
|
||
|
|
/*
|
||
|
|
FUNCTION
|
||
|
|
<<scalbn>>, <<scalbnf>>, <<scalbln>>, <<scalblnf>>--scale by power of FLT_RADIX (=2)
|
||
|
|
INDEX
|
||
|
|
scalbn
|
||
|
|
INDEX
|
||
|
|
scalbnf
|
||
|
|
INDEX
|
||
|
|
scalbln
|
||
|
|
INDEX
|
||
|
|
scalblnf
|
||
|
|
|
||
|
|
ANSI_SYNOPSIS
|
||
|
|
#include <math.h>
|
||
|
|
double scalbn(double <[x]>, int <[n]>);
|
||
|
|
float scalbnf(float <[x]>, int <[n]>);
|
||
|
|
double scalbln(double <[x]>, long int <[n]>);
|
||
|
|
float scalblnf(float <[x]>, long int <[n]>);
|
||
|
|
|
||
|
|
DESCRIPTION
|
||
|
|
The <<scalbn>> and <<scalbln>> functions compute
|
||
|
|
@ifnottex
|
||
|
|
<[x]> times FLT_RADIX to the power <[n]>.
|
||
|
|
@end ifnottex
|
||
|
|
@tex
|
||
|
|
$x \cdot FLT\_RADIX^n$.
|
||
|
|
@end tex
|
||
|
|
efficiently. The result is computed by manipulating the exponent, rather than
|
||
|
|
by actually performing an exponentiation or multiplication. In this
|
||
|
|
floating-point implementation FLT_RADIX=2, which makes the <<scalbn>>
|
||
|
|
functions equivalent to the <<ldexp>> functions.
|
||
|
|
|
||
|
|
RETURNS
|
||
|
|
<[x]> times 2 to the power <[n]>. A range error may occur.
|
||
|
|
|
||
|
|
PORTABILITY
|
||
|
|
ANSI C, POSIX
|
||
|
|
|
||
|
|
SEEALSO
|
||
|
|
<<ldexp>>
|
||
|
|
|
||
|
|
*/
|
||
|
|
|
||
|
|
/*
|
||
|
|
* 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 "fdlibm.h"
|
||
|
|
|
||
|
|
#ifndef _DOUBLE_IS_32BITS
|
||
|
|
|
||
|
|
#ifdef __STDC__
|
||
|
|
static const double
|
||
|
|
#else
|
||
|
|
static double
|
||
|
|
#endif
|
||
|
|
two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
|
||
|
|
twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
|
||
|
|
huge = 1.0e+300,
|
||
|
|
tiny = 1.0e-300;
|
||
|
|
|
||
|
|
#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*copysign(huge,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*copysign(huge,x); /*overflow*/
|
||
|
|
else return tiny*copysign(tiny,x); /*underflow*/
|
||
|
|
}
|
||
|
|
k += 54; /* subnormal result */
|
||
|
|
SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
|
||
|
|
return x*twom54;
|
||
|
|
}
|
||
|
|
|
||
|
|
#endif /* _DOUBLE_IS_32BITS */
|