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lightning-sunbird  0.9+nobinonly
e_remainder.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
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00032  * use your version of this file under the terms of the MPL, indicate your
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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 /* @(#)e_remainder.c 1.3 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 /* __ieee754_remainder(x,p)
00053  * Return :                  
00054  *     returns  x REM p  =  x - [x/p]*p as if in infinite 
00055  *     precise arithmetic, where [x/p] is the (infinite bit) 
00056  *     integer nearest x/p (in half way case choose the even one).
00057  * Method : 
00058  *     Based on fmod() return x-[x/p]chopped*p exactlp.
00059  */
00060 
00061 #include "fdlibm.h"
00062 
00063 #ifdef __STDC__
00064 static const double zero = 0.0;
00065 #else
00066 static double zero = 0.0;
00067 #endif
00068 
00069 
00070 #ifdef __STDC__
00071        double __ieee754_remainder(double x, double p)
00072 #else
00073        double __ieee754_remainder(x,p)
00074        double x,p;
00075 #endif
00076 {
00077         fd_twoints u;
00078        int hx,hp;
00079        unsigned sx,lx,lp;
00080        double p_half;
00081 
00082         u.d = x;
00083        hx = __HI(u);        /* high word of x */
00084        lx = __LO(u);        /* low  word of x */
00085         u.d = p;
00086        hp = __HI(u);        /* high word of p */
00087        lp = __LO(u);        /* low  word of p */
00088        sx = hx&0x80000000;
00089        hp &= 0x7fffffff;
00090        hx &= 0x7fffffff;
00091 
00092     /* purge off exception values */
00093        if((hp|lp)==0) return (x*p)/(x*p);        /* p = 0 */
00094        if((hx>=0x7ff00000)||                     /* x not finite */
00095          ((hp>=0x7ff00000)&&                     /* p is NaN */
00096          (((hp-0x7ff00000)|lp)!=0)))
00097            return (x*p)/(x*p);
00098 
00099 
00100        if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p);   /* now x < 2p */
00101        if (((hx-hp)|(lx-lp))==0) return zero*x;
00102        x  = fd_fabs(x);
00103        p  = fd_fabs(p);
00104        if (hp<0x00200000) {
00105            if(x+x>p) {
00106               x-=p;
00107               if(x+x>=p) x -= p;
00108            }
00109        } else {
00110            p_half = 0.5*p;
00111            if(x>p_half) {
00112               x-=p;
00113               if(x>=p_half) x -= p;
00114            }
00115        }
00116         u.d = x;
00117        __HI(u) ^= sx;
00118         x = u.d;
00119        return x;
00120 }