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lightning-sunbird  0.9+nobinonly
s_rint.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_rint.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 /*
00053  * rint(x)
00054  * Return x rounded to integral value according to the prevailing
00055  * rounding mode.
00056  * Method:
00057  *     Using floating addition.
00058  * Exception:
00059  *     Inexact flag raised if x not equal to rint(x).
00060  */
00061 
00062 #include "fdlibm.h"
00063 
00064 #ifdef __STDC__
00065 static const double
00066 #else
00067 static double 
00068 #endif
00069 TWO52[2]={
00070   4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
00071  -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
00072 };
00073 
00074 #ifdef __STDC__
00075        double fd_rint(double x)
00076 #else
00077        double fd_rint(x)
00078        double x;
00079 #endif
00080 {
00081        int i0,j0,sx;
00082        unsigned i,i1;
00083        double w,t;
00084         fd_twoints u;
00085 
00086         u.d = x;
00087        i0 =  __HI(u);
00088        sx = (i0>>31)&1;
00089        i1 =  __LO(u);
00090        j0 = ((i0>>20)&0x7ff)-0x3ff;
00091        if(j0<20) {
00092            if(j0<0) {       
00093               if(((i0&0x7fffffff)|i1)==0) return x;
00094               i1 |= (i0&0x0fffff);
00095               i0 &= 0xfffe0000;
00096               i0 |= ((i1|-(int)i1)>>12)&0x80000;
00097                 u.d = x;
00098               __HI(u)=i0;
00099                 x = u.d;
00100                w = TWO52[sx]+x;
00101                t =  w-TWO52[sx];
00102                 u.d = t;
00103                i0 = __HI(u);
00104                __HI(u) = (i0&0x7fffffff)|(sx<<31);
00105                 t = u.d;
00106                return t;
00107            } else {
00108               i = (0x000fffff)>>j0;
00109               if(((i0&i)|i1)==0) return x; /* x is integral */
00110               i>>=1;
00111               if(((i0&i)|i1)!=0) {
00112                   if(j0==19) i1 = 0x40000000; else
00113                   i0 = (i0&(~i))|((0x20000)>>j0);
00114               }
00115            }
00116        } else if (j0>51) {
00117            if(j0==0x400) return x+x;      /* inf or NaN */
00118            else return x;          /* x is integral */
00119        } else {
00120            i = ((unsigned)(0xffffffff))>>(j0-20);
00121            if((i1&i)==0) return x; /* x is integral */
00122            i>>=1;
00123            if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));
00124        }
00125         u.d = x;
00126        __HI(u) = i0;
00127        __LO(u) = i1;
00128         x = u.d;
00129        w = TWO52[sx]+x;
00130        return w-TWO52[sx];
00131 }