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lightning-sunbird  0.9+nobinonly
s_floor.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_floor.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  * floor(x)
00054  * Return x rounded toward -inf to integral value
00055  * Method:
00056  *     Bit twiddling.
00057  * Exception:
00058  *     Inexact flag raised if x not equal to floor(x).
00059  */
00060 
00061 #include "fdlibm.h"
00062 
00063 #ifdef __STDC__
00064 static const double really_big = 1.0e300;
00065 #else
00066 static double really_big = 1.0e300;
00067 #endif
00068 
00069 #ifdef __STDC__
00070        double fd_floor(double x)
00071 #else
00072        double fd_floor(x)
00073        double x;
00074 #endif
00075 {
00076         fd_twoints u;
00077        int i0,i1,j0;
00078        unsigned i,j;
00079         u.d = x;
00080        i0 =  __HI(u);
00081        i1 =  __LO(u);
00082        j0 = ((i0>>20)&0x7ff)-0x3ff;
00083        if(j0<20) {
00084            if(j0<0) {       /* raise inexact if x != 0 */
00085               if(really_big+x>0.0) {/* return 0*sign(x) if |x|<1 */
00086                   if(i0>=0) {i0=i1=0;} 
00087                   else if(((i0&0x7fffffff)|i1)!=0)
00088                      { i0=0xbff00000;i1=0;}
00089               }
00090            } else {
00091               i = (0x000fffff)>>j0;
00092               if(((i0&i)|i1)==0) return x; /* x is integral */
00093               if(really_big+x>0.0) {      /* raise inexact flag */
00094                   if(i0<0) i0 += (0x00100000)>>j0;
00095                   i0 &= (~i); i1=0;
00096               }
00097            }
00098        } else if (j0>51) {
00099            if(j0==0x400) return x+x;      /* inf or NaN */
00100            else return x;          /* x is integral */
00101        } else {
00102            i = ((unsigned)(0xffffffff))>>(j0-20);
00103            if((i1&i)==0) return x; /* x is integral */
00104            if(really_big+x>0.0) {         /* raise inexact flag */
00105               if(i0<0) {
00106                   if(j0==20) i0+=1; 
00107                   else {
00108                      j = i1+(1<<(52-j0));
00109                      if((int)j<i1) i0 +=1 ;      /* got a carry */
00110                      i1=j;
00111                   }
00112               }
00113               i1 &= (~i);
00114            }
00115        }
00116         u.d = x;
00117        __HI(u) = i0;
00118        __LO(u) = i1;
00119         x = u.d;
00120        return x;
00121 }