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lightning-sunbird  0.9+nobinonly
s_frexp.c
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00001 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
00002  *
00003  * ***** BEGIN LICENSE BLOCK *****
00004  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
00005  *
00006  * The contents of this file are subject to the Mozilla Public License Version
00007  * 1.1 (the "License"); you may not use this file except in compliance with
00008  * the License. You may obtain a copy of the License at
00009  * http://www.mozilla.org/MPL/
00010  *
00011  * Software distributed under the License is distributed on an "AS IS" basis,
00012  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
00013  * for the specific language governing rights and limitations under the
00014  * License.
00015  *
00016  * The Original Code is Mozilla Communicator client code, released
00017  * March 31, 1998.
00018  *
00019  * The Initial Developer of the Original Code is
00020  * Sun Microsystems, Inc.
00021  * Portions created by the Initial Developer are Copyright (C) 1998
00022  * the Initial Developer. All Rights Reserved.
00023  *
00024  * Contributor(s):
00025  *
00026  * Alternatively, the contents of this file may be used under the terms of
00027  * either of the GNU General Public License Version 2 or later (the "GPL"),
00028  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
00029  * in which case the provisions of the GPL or the LGPL are applicable instead
00030  * of those above. If you wish to allow use of your version of this file only
00031  * under the terms of either the GPL or the LGPL, and not to allow others to
00032  * use your version of this file under the terms of the MPL, indicate your
00033  * decision by deleting the provisions above and replace them with the notice
00034  * and other provisions required by the GPL or the LGPL. If you do not delete
00035  * the provisions above, a recipient may use your version of this file under
00036  * the terms of any one of the MPL, the GPL or the LGPL.
00037  *
00038  * ***** END LICENSE BLOCK ***** */
00039 
00040 /* @(#)s_frexp.c 1.4 95/01/18 */
00041 /*
00042  * ====================================================
00043  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
00044  *
00045  * Developed at SunSoft, a Sun Microsystems, Inc. business.
00046  * Permission to use, copy, modify, and distribute this
00047  * software is freely granted, provided that this notice 
00048  * is preserved.
00049  * ====================================================
00050  */
00051 
00052 /*
00053  * for non-zero x 
00054  *     x = frexp(arg,&exp);
00055  * return a double fp quantity x such that 0.5 <= |x| <1.0
00056  * and the corresponding binary exponent "exp". That is
00057  *     arg = x*2^exp.
00058  * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg 
00059  * with *exp=0. 
00060  */
00061 
00062 #include "fdlibm.h"
00063 
00064 #ifdef __STDC__
00065 static const double
00066 #else
00067 static double
00068 #endif
00069 two54 =  1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
00070 
00071 #ifdef __STDC__
00072        double fd_frexp(double x, int *eptr)
00073 #else
00074        double fd_frexp(x, eptr)
00075        double x; int *eptr;
00076 #endif
00077 {
00078        int  hx, ix, lx;
00079         fd_twoints u;
00080         u.d = x;
00081        hx = __HI(u);
00082        ix = 0x7fffffff&hx;
00083        lx = __LO(u);
00084        *eptr = 0;
00085        if(ix>=0x7ff00000||((ix|lx)==0)) return x;       /* 0,inf,nan */
00086        if (ix<0x00100000) {        /* subnormal */
00087            x *= two54;
00088             u.d = x;
00089            hx = __HI(u);
00090            ix = hx&0x7fffffff;
00091            *eptr = -54;
00092        }
00093        *eptr += (ix>>20)-1022;
00094        hx = (hx&0x800fffff)|0x3fe00000;
00095         u.d = x;
00096        __HI(u) = hx;
00097         x = u.d;
00098        return x;
00099 }