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/* @(#)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.
* ====================================================
*/
#ifndef lint
static char rcsid[] = "$FreeBSD$";
#endif
/*
* scalbnl (long double x, int n)
* scalbnl(x,n) returns x* 2**n computed by exponent
* manipulation rather than by actually performing an
* exponentiation or a multiplication.
*/
/*
* We assume that a long double has a 15-bit exponent. On systems
* where long double is the same as double, scalbnl() is an alias
* for scalbn(), so we don't use this routine.
*/
#include <sys/cdefs.h>
#include <float.h>
#include <math.h>
#include "fpmath.h"
#if LDBL_MAX_EXP != 0x4000
#error "Unsupported long double format"
#endif
static const long double
huge = 0x1p16000L,
tiny = 0x1p-16000L;
long double
scalbnl (long double x, int n)
{
union IEEEl2bits u;
int k;
u.e = x;
k = u.bits.exp; /* extract exponent */
if (k==0) { /* 0 or subnormal x */
if ((u.bits.manh|u.bits.manl)==0) return x; /* +-0 */
u.e *= 0x1p+128;
k = u.bits.exp - 128;
if (n< -50000) return tiny*x; /*underflow*/
}
if (k==0x7fff) return x+x; /* NaN or Inf */
k = k+n;
if (k >= 0x7fff) return huge*copysignl(huge,x); /* overflow */
if (k > 0) /* normal result */
{u.bits.exp = k; return u.e;}
if (k <= -128)
if (n > 50000) /* in case integer overflow in n+k */
return huge*copysign(huge,x); /*overflow*/
else return tiny*copysign(tiny,x); /*underflow*/
k += 128; /* subnormal result */
u.bits.exp = k;
return u.e*0x1p-128;
}
__strong_reference(scalbnl, ldexpl);
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