Code coverage report for fdlibm/scalbn.js

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//
// ====================================================
// 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.
// ====================================================
//
 
//
// copysign(double x, double y)
// copysign(x,y) returns a value with the magnitude of x and
// with the sign bit of y.
//
function copysign(x, y)
{
    return _ConstructDouble((_DoubleHi(x) & 0x7fffffff) | (_DoubleHi(y) & 0x80000000), _DoubleLo(x));
}
 
// 
// 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.
//
var huge = 1e300;
var tiny = 1e-300;
var two54 = Math.pow(2, 54);
var twom54 = Math.pow(2, -54);
 
function scalbn(x, n)
 
{
    var  k,hx,lx;
    hx = _DoubleHi(x);
    lx = _DoubleLo(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 = _DoubleHi(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 */
        //_DoubleHi(x) = (hx&0x800fffff)|(k<<20);
        x = _ConstructDouble((hx&0x800fffff)|(k<<20), _DoubleLo(x));
        return x;
    }
    if (k <= -54)
        Iif (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);
    x = _ConstructDouble((hx&0x800fffff)|(k<<20), _DoubleLo(x));
    return x*twom54;
}