1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/os/ossrv/genericopenlibs/cstdlib/LMATH/S_SCALBN.C	Fri Jun 15 03:10:57 2012 +0200
     1.3 @@ -0,0 +1,106 @@
     1.4 +/* S_SCALBN.C
     1.5 + * 
     1.6 + * Portions Copyright (c) 1993-1999 Nokia Corporation and/or its subsidiary(-ies).
     1.7 + * All rights reserved.
     1.8 + */
     1.9 +
    1.10 +
    1.11 +/* @(#)s_scalbn.c 5.1 93/09/24 */
    1.12 +/*
    1.13 + * ====================================================
    1.14 + * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
    1.15 + *
    1.16 + * Developed at SunPro, a Sun Microsystems, Inc. business.
    1.17 + * Permission to use, copy, modify, and distribute this
    1.18 + * software is freely granted, provided that this notice 
    1.19 + * is preserved.
    1.20 + * ====================================================
    1.21 + */
    1.22 +
    1.23 +/*
    1.24 +FUNCTION
    1.25 +<<scalbn>>, <<scalbnf>>---scale by integer
    1.26 +INDEX
    1.27 +	scalbn
    1.28 +INDEX
    1.29 +	scalbnf
    1.30 +
    1.31 +ANSI_SYNOPSIS
    1.32 +	#include <math.h>
    1.33 +	double scalbn(double <[x]>, int <[y]>);
    1.34 +	float scalbnf(float <[x]>, int <[y]>);
    1.35 +
    1.36 +TRAD_SYNOPSIS
    1.37 +	#include <math.h>
    1.38 +	double scalbn(<[x]>,<[y]>)
    1.39 +	double <[x]>;
    1.40 +	int <[y]>;
    1.41 +	float scalbnf(<[x]>,<[y]>)
    1.42 +	float <[x]>;
    1.43 +	int <[y]>;
    1.44 +
    1.45 +DESCRIPTION
    1.46 +<<scalbn>> and <<scalbnf>> scale <[x]> by <[n]>, returning <[x]> times
    1.47 +2 to the power <[n]>.  The result is computed by manipulating the
    1.48 +exponent, rather than by actually performing an exponentiation or
    1.49 +multiplication.
    1.50 +
    1.51 +RETURNS
    1.52 +<[x]> times 2 to the power <[n]>.
    1.53 +
    1.54 +PORTABILITY
    1.55 +Neither <<scalbn>> nor <<scalbnf>> is required by ANSI C or by the System V
    1.56 +Interface Definition (Issue 2).
    1.57 +
    1.58 +*/
    1.59 +
    1.60 +/* 
    1.61 + * scalbn (double x, int n)
    1.62 + * scalbn(x,n) returns x* 2**n  computed by  exponent  
    1.63 + * manipulation rather than by actually performing an 
    1.64 + * exponentiation or a multiplication.
    1.65 + */
    1.66 +
    1.67 +#include "FDLIBM.H"
    1.68 +
    1.69 +static const double
    1.70 +two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
    1.71 +twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
    1.72 +huge   = 1.0e+300,
    1.73 +tiny   = 1.0e-300;
    1.74 +
    1.75 +/**
    1.76 +Scales x by n, returning x times
    1.77 +2 to the power n.  The result is computed by manipulating the
    1.78 +exponent, rather than by actually performing an exponentiation or
    1.79 +multiplication.
    1.80 +@return x times 2 to the power n.
    1.81 +@param x floating point value
    1.82 +@param n integer power
    1.83 +*/
    1.84 +EXPORT_C double scalbn (double x, int n) __SOFTFP
    1.85 +{
    1.86 +	__int32_t  k,hx,lx;
    1.87 +	EXTRACT_WORDS(hx,lx,x);
    1.88 +        k = (hx&0x7ff00000)>>20;		/* extract exponent */
    1.89 +        if (k==0) {				/* 0 or subnormal x */
    1.90 +            if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
    1.91 +	    x *= two54; 
    1.92 +	    GET_HIGH_WORD(hx,x);
    1.93 +	    k = ((hx&0x7ff00000)>>20) - 54; 
    1.94 +            if (n< -50000) return tiny*x; 	/*underflow*/
    1.95 +	    }
    1.96 +        if (k==0x7ff) return x+x;		/* NaN or Inf */
    1.97 +        k = k+n; 
    1.98 +        if (k >  0x7fe) return huge*copysign(huge,x); /* overflow  */
    1.99 +        if (k > 0) 				/* normal result */
   1.100 +	    {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}
   1.101 +        if (k <= -54) {
   1.102 +            if (n > 50000) 	/* in case integer overflow in n+k */
   1.103 +			     return huge*copysign(huge,x);	/*overflow*/
   1.104 +			else return tiny*copysign(tiny,x); 	/*underflow*/
   1.105 +		}
   1.106 +        k += 54;				/* subnormal result */
   1.107 +	SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
   1.108 +        return x*twom54;
   1.109 +}