/* @(#)s_scalbn.c 1.3 95/01/18 */

/*

 * ====================================================

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunSoft, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice 

 * is preserved.

 * ====================================================

 */

/* 

 * 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"

#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

{

	int  k,hx,lx;

	hx = __HI(x);

	lx = __LO(x);

        k = (hx&0x7ff00000)>>20;		/* extract exponent */

        if (k==0) {				/* 0 or subnormal x */

            if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */

	    x *= two54; 

	    hx = __HI(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 */

	    {__HI(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 */

        __HI(x) = (hx&0x800fffff)|(k<<20);

        return x*twom54;

}