1 /*
2  * Copyright (c) 1998, 2001, Oracle and/or its affiliates. All rights reserved.
3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4  *
5  * This code is free software; you can redistribute it and/or modify it
6  * under the terms of the GNU General Public License version 2 only, as
7  * published by the Free Software Foundation.  Oracle designates this
8  * particular file as subject to the "Classpath" exception as provided
9  * by Oracle in the LICENSE file that accompanied this code.
10  *
11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
18  * 2 along with this work; if not, write to the Free Software Foundation,
19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20  *
21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22  * or visit www.oracle.com if you need additional information or have any
23  * questions.
24  */
25 
26 /*
27  * ceil(x)
28  * Return x rounded toward -inf to integral value
29  * Method:
30  *      Bit twiddling.
31  * Exception:
32  *      Inexact flag raised if x not equal to ceil(x).
33  */
34 
35 #include "fdlibm.h"
36 
37 #ifdef __STDC__
38 static const double huge = 1.0e300;
39 #else
40 static double huge = 1.0e300;
41 #endif
42 
43 #ifdef __STDC__
ceil(double x)44         double ceil(double x)
45 #else
46         double ceil(x)
47         double x;
48 #endif
49 {
50         int i0,i1,j0;
51         unsigned i,j;
52         i0 =  __HI(x);
53         i1 =  __LO(x);
54         j0 = ((i0>>20)&0x7ff)-0x3ff;
55         if(j0<20) {
56             if(j0<0) {  /* raise inexact if x != 0 */
57                 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
58                     if(i0<0) {i0=0x80000000;i1=0;}
59                     else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
60                 }
61             } else {
62                 i = (0x000fffff)>>j0;
63                 if(((i0&i)|i1)==0) return x; /* x is integral */
64                 if(huge+x>0.0) {        /* raise inexact flag */
65                     if(i0>0) i0 += (0x00100000)>>j0;
66                     i0 &= (~i); i1=0;
67                 }
68             }
69         } else if (j0>51) {
70             if(j0==0x400) return x+x;   /* inf or NaN */
71             else return x;              /* x is integral */
72         } else {
73             i = ((unsigned)(0xffffffff))>>(j0-20);
74             if((i1&i)==0) return x;     /* x is integral */
75             if(huge+x>0.0) {            /* raise inexact flag */
76                 if(i0>0) {
77                     if(j0==20) i0+=1;
78                     else {
79                         j = i1 + (1<<(52-j0));
80                         if(j<i1) i0+=1; /* got a carry */
81                         i1 = j;
82                     }
83                 }
84                 i1 &= (~i);
85             }
86         }
87         __HI(x) = i0;
88         __LO(x) = i1;
89         return x;
90 }
91