frexp.c

/*
 *                               POK header
 * 
 * The following file is a part of the POK project. Any modification should
 * made according to the POK licence. You CANNOT use this file or a part of
 * this file is this part of a file for your own project
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2009 POK team 
 *
 * Created by julien on Fri Jan 30 14:41:34 2009 
 */

/* @(#)s_frexp.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.
 * ====================================================
 */

/*
 * for non-zero x
 *      x = frexp(arg,&exp);
 * return a double fp quantity x such that 0.5 <= |x| <1.0
 * and the corresponding binary exponent "exp". That is
 *      arg = x*2^exp.
 * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
 * with *exp=0.
 */

#ifdef POK_NEEDS_LIBMATH

#include <libm.h>
#include "math_private.h"

static const double
two54 =  1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */

double
frexp(double x, int *eptr)
{
        int32_t hx, ix, lx;
        EXTRACT_WORDS(hx,lx,x);
        ix = 0x7fffffff&hx;
        *eptr = 0;
        if(ix>=0x7ff00000||((ix|lx)==0)) return x;      /* 0,inf,nan */
        if (ix<0x00100000) {            /* subnormal */
            x *= two54;
            GET_HIGH_WORD(hx,x);
            ix = hx&0x7fffffff;
            *eptr = -54;
        }
        *eptr += ((uint32_t)ix>>20)-1022;
        hx = (hx&0x800fffff)|0x3fe00000;
        SET_HIGH_WORD(x,hx);
        return x;
}

#endif