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       ---
       s_frexp.c (1328B)
       ---
            1 /* @(#)s_frexp.c 5.1 93/09/24 */
            2 /*
            3  * ====================================================
            4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
            5  *
            6  * Developed at SunPro, a Sun Microsystems, Inc. business.
            7  * Permission to use, copy, modify, and distribute this
            8  * software is freely granted, provided that this notice
            9  * is preserved.
           10  * ====================================================
           11  */
           12 
           13 #ifndef lint
           14 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_frexp.c,v 1.8 2002/05/28 18:15:04 alfred Exp $";
           15 #endif
           16 
           17 /*
           18  * for non-zero x
           19  *        x = frexp(arg,&exp);
           20  * return a double fp quantity x such that 0.5 <= |x| <1.0
           21  * and the corresponding binary exponent "exp". That is
           22  *        arg = x*2^exp.
           23  * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
           24  * with *exp=0.
           25  */
           26 
           27 #include "math.h"
           28 #include "math_private.h"
           29 
           30 static const double
           31 two54 =  1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
           32 
           33 double
           34 frexp(double x, int *eptr)
           35 {
           36         int32_t hx, ix, lx;
           37         EXTRACT_WORDS(hx,lx,x);
           38         ix = 0x7fffffff&hx;
           39         *eptr = 0;
           40         if(ix>=0x7ff00000||((ix|lx)==0)) return x;        /* 0,inf,nan */
           41         if (ix<0x00100000) {                /* subnormal */
           42             x *= two54;
           43             GET_HIGH_WORD(hx,x);
           44             ix = hx&0x7fffffff;
           45             *eptr = -54;
           46         }
           47         *eptr += (ix>>20)-1022;
           48         hx = (hx&0x800fffff)|0x3fe00000;
           49         SET_HIGH_WORD(x,hx);
           50         return x;
           51 }