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/* __ieee754_remainder(x,p)
27 * Return :
28 * returns x REM p = x - [x/p]*p as if in infinite
29 * precise arithmetic, where [x/p] is the (infinite bit)
30 * integer nearest x/p (in half way case choose the even one).
31 * Method :
32 * Based on fmod() return x-[x/p]chopped*p exactlp.
33 */
34
35#include "fdlibm.h"
36
37#ifdef __STDC__
38static const double zero = 0.0;
39#else
40static double zero = 0.0;
41#endif
42
43
44#ifdef __STDC__
45 double __ieee754_remainder(double x, double p)
46#else
47 double __ieee754_remainder(x,p)
48 double x,p;
49#endif
50{
51 int hx,hp;
52 unsigned sx,lx,lp;
53 double p_half;
54
55 hx = __HI(x); /* high word of x */
56 lx = __LO(x); /* low word of x */
57 hp = __HI(p); /* high word of p */
58 lp = __LO(p); /* low word of p */
59 sx = hx&0x80000000;
60 hp &= 0x7fffffff;
61 hx &= 0x7fffffff;
62
63 /* purge off exception values */
64 if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */
65 if((hx>=0x7ff00000)|| /* x not finite */
66 ((hp>=0x7ff00000)&& /* p is NaN */
67 (((hp-0x7ff00000)|lp)!=0)))
68 return (x*p)/(x*p);
69
70
71 if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */
72 if (((hx-hp)|(lx-lp))==0) return zero*x;
73 x = fabs(x);
74 p = fabs(p);
75 if (hp<0x00200000) {
76 if(x+x>p) {
77 x-=p;
78 if(x+x>=p) x -= p;
79 }
80 } else {
81 p_half = 0.5*p;
82 if(x>p_half) {
83 x-=p;
84 if(x>=p_half) x -= p;
85 }
86 }
87 __HI(x) ^= sx;
88 return x;
89}
90