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lightning-sunbird  0.9+nobinonly
s_modf.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_modf.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  * modf(double x, double *iptr) 
00054  * return fraction part of x, and return x's integral part in *iptr.
00055  * Method:
00056  *     Bit twiddling.
00057  *
00058  * Exception:
00059  *     No exception.
00060  */
00061 
00062 #include "fdlibm.h"
00063 
00064 #ifdef __STDC__
00065 static const double one = 1.0;
00066 #else
00067 static double one = 1.0;
00068 #endif
00069 
00070 #ifdef __STDC__
00071        double fd_modf(double x, double *iptr)
00072 #else
00073        double fd_modf(x, iptr)
00074        double x,*iptr;
00075 #endif
00076 {
00077        int i0,i1,j0;
00078        unsigned i;
00079         fd_twoints u;
00080         u.d = x;
00081        i0 =  __HI(u);              /* high x */
00082        i1 =  __LO(u);              /* low  x */
00083        j0 = ((i0>>20)&0x7ff)-0x3ff;       /* exponent of x */
00084        if(j0<20) {                 /* integer part in high x */
00085            if(j0<0) {                     /* |x|<1 */
00086                 u.d = *iptr;
00087               __HI(u) = i0&0x80000000;
00088               __LO(u) = 0;         /* *iptr = +-0 */
00089                 *iptr = u.d;
00090               return x;
00091            } else {
00092               i = (0x000fffff)>>j0;
00093               if(((i0&i)|i1)==0) {        /* x is integral */
00094                   *iptr = x;
00095                     u.d = x;
00096                   __HI(u) &= 0x80000000;
00097                   __LO(u)  = 0;    /* return +-0 */
00098                     x = u.d;
00099                   return x;
00100               } else {
00101                     u.d = *iptr;
00102                   __HI(u) = i0&(~i);
00103                   __LO(u) = 0;
00104                     *iptr = u.d;
00105                   return x - *iptr;
00106               }
00107            }
00108        } else if (j0>51) {         /* no fraction part */
00109            *iptr = x*one;
00110             u.d = x;
00111            __HI(u) &= 0x80000000;
00112            __LO(u)  = 0;    /* return +-0 */
00113             x = u.d;
00114            return x;
00115        } else {                    /* fraction part in low x */
00116            i = ((unsigned)(0xffffffff))>>(j0-20);
00117            if((i1&i)==0) {         /* x is integral */
00118               *iptr = x;
00119                 u.d = x;
00120               __HI(u) &= 0x80000000;
00121               __LO(u)  = 0; /* return +-0 */
00122                 x = u.d;
00123               return x;
00124            } else {
00125                 u.d = *iptr;
00126               __HI(u) = i0;
00127               __LO(u) = i1&(~i);
00128                 *iptr = u.d;
00129               return x - *iptr;
00130            }
00131        }
00132 }