/* S_SCALBN.C

 * 

 * Portions Copyright (c) 1993-1999 Nokia Corporation and/or its subsidiary(-ies).

 * All rights reserved.

 */

/* @(#)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>>---scale by integer

INDEX

	scalbn

INDEX

	scalbnf

ANSI_SYNOPSIS

	#include <math.h>

	double scalbn(double <[x]>, int <[y]>);

	float scalbnf(float <[x]>, int <[y]>);

TRAD_SYNOPSIS

	#include <math.h>

	double scalbn(<[x]>,<[y]>)

	double <[x]>;

	int <[y]>;

	float scalbnf(<[x]>,<[y]>)

	float <[x]>;

	int <[y]>;

DESCRIPTION

<<scalbn>> and <<scalbnf>> scale <[x]> by <[n]>, returning <[x]> times

2 to the power <[n]>.  The result is computed by manipulating the

exponent, rather than by actually performing an exponentiation or

multiplication.

RETURNS

<[x]> times 2 to the power <[n]>.

PORTABILITY

Neither <<scalbn>> nor <<scalbnf>> is required by ANSI C or by the System V

Interface Definition (Issue 2).

*/

/* 

 * 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"

static const double

two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */

twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */

huge   = 1.0e+300,

tiny   = 1.0e-300;

/**

Scales x by n, returning x times

2 to the power n.  The result is computed by manipulating the

exponent, rather than by actually performing an exponentiation or

multiplication.

@return x times 2 to the power n.

@param x floating point value

@param n integer power

*/

EXPORT_C double scalbn (double x, int n) __SOFTFP

{

	__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;

}