src/fdlibm/e_remainder.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Communicator client code, released
 * March 31, 1998.
 *
 * The Initial Developer of the Original Code is
 * Sun Microsystems, Inc.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

/* @(#)e_remainder.c 1.3 95/01/18 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunSoft, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice 
 * is preserved.
 * ====================================================
 */

/* __ieee754_remainder(x,p)
 * Return :                  
 *      returns  x REM p  =  x - [x/p]*p as if in infinite 
 *      precise arithmetic, where [x/p] is the (infinite bit) 
 *      integer nearest x/p (in half way case choose the even one).
 * Method : 
 *      Based on fmod() return x-[x/p]chopped*p exactlp.
 */

#include "fdlibm.h"

#ifdef __STDC__
static const double zero = 0.0;
#else
static double zero = 0.0;
#endif


#ifdef __STDC__
        double __ieee754_remainder(double x, double p)
#else
        double __ieee754_remainder(x,p)
        double x,p;
#endif
{
        fd_twoints u;
        int hx,hp;
        unsigned sx,lx,lp;
        double p_half;

        u.d = x;
        hx = __HI(u);           /* high word of x */
        lx = __LO(u);           /* low  word of x */
        u.d = p;
        hp = __HI(u);           /* high word of p */
        lp = __LO(u);           /* low  word of p */
        sx = hx&0x80000000;
        hp &= 0x7fffffff;
        hx &= 0x7fffffff;

    /* purge off exception values */
        if((hp|lp)==0) return (x*p)/(x*p);      /* p = 0 */
        if((hx>=0x7ff00000)||                   /* x not finite */
          ((hp>=0x7ff00000)&&                   /* p is NaN */
          (((hp-0x7ff00000)|lp)!=0)))
            return (x*p)/(x*p);


        if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p);  /* now x < 2p */
        if (((hx-hp)|(lx-lp))==0) return zero*x;
        x  = fd_fabs(x);
        p  = fd_fabs(p);
        if (hp<0x00200000) {
            if(x+x>p) {
                x-=p;
                if(x+x>=p) x -= p;
            }
        } else {
            p_half = 0.5*p;
            if(x>p_half) {
                x-=p;
                if(x>=p_half) x -= p;
            }
        }
        u.d = x;
        __HI(u) ^= sx;
        x = u.d;
        return x;
}
1	/* -- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 --
2	*
3	* *** BEGIN LICENSE BLOCK ***
4	* Version: MPL 1.1/GPL 2.0/LGPL 2.1
5	*
6	* The contents of this file are subject to the Mozilla Public License Version
7	* 1.1 (the "License"); you may not use this file except in compliance with
8	* the License. You may obtain a copy of the License at
9	* http://www.mozilla.org/MPL/
10	*
11	* Software distributed under the License is distributed on an "AS IS" basis,
12	* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
13	* for the specific language governing rights and limitations under the
14	* License.
15	*
16	* The Original Code is Mozilla Communicator client code, released
17	* March 31, 1998.
18	*
19	* The Initial Developer of the Original Code is
20	* Sun Microsystems, Inc.
21	* Portions created by the Initial Developer are Copyright (C) 1998
22	* the Initial Developer. All Rights Reserved.
23	*
24	* Contributor(s):
25	*
26	* Alternatively, the contents of this file may be used under the terms of
27	* either of the GNU General Public License Version 2 or later (the "GPL"),
28	* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
29	* in which case the provisions of the GPL or the LGPL are applicable instead
30	* of those above. If you wish to allow use of your version of this file only
31	* under the terms of either the GPL or the LGPL, and not to allow others to
32	* use your version of this file under the terms of the MPL, indicate your
33	* decision by deleting the provisions above and replace them with the notice
34	* and other provisions required by the GPL or the LGPL. If you do not delete
35	* the provisions above, a recipient may use your version of this file under
36	* the terms of any one of the MPL, the GPL or the LGPL.
37	*
38	* *** END LICENSE BLOCK *** */
39
40	/* @(#)e_remainder.c 1.3 95/01/18 */
41	/*
42	* ====================================================
43	* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
44	*
45	* Developed at SunSoft, a Sun Microsystems, Inc. business.
46	* Permission to use, copy, modify, and distribute this
47	* software is freely granted, provided that this notice
48	* is preserved.
49	* ====================================================
50	*/
51
52	/* __ieee754_remainder(x,p)
53	* Return :
54	* returns x REM p = x - [x/p]*p as if in infinite
55	* precise arithmetic, where [x/p] is the (infinite bit)
56	* integer nearest x/p (in half way case choose the even one).
57	* Method :
58	* Based on fmod() return x-[x/p]chopped*p exactlp.
59	*/
60
61	#include "fdlibm.h"
62
63	#ifdef __STDC__
64	static const double zero = 0.0;
65	#else
66	static double zero = 0.0;
67	#endif
68
69
70	#ifdef __STDC__
71	double __ieee754_remainder(double x, double p)
72	#else
73	double __ieee754_remainder(x,p)
74	double x,p;
75	#endif
76	{
77	fd_twoints u;
78	int hx,hp;
79	unsigned sx,lx,lp;
80	double p_half;
81
82	u.d = x;
83	hx = __HI(u); /* high word of x */
84	lx = __LO(u); /* low word of x */
85	u.d = p;
86	hp = __HI(u); /* high word of p */
87	lp = __LO(u); /* low word of p */
88	sx = hx&0x80000000;
89	hp &= 0x7fffffff;
90	hx &= 0x7fffffff;
91
92	/* purge off exception values */
93	if((hp\|lp)==0) return (xp)/(xp); /* p = 0 */
94	if((hx>=0x7ff00000)\|\| /* x not finite */
95	((hp>=0x7ff00000)&& /* p is NaN */
96	(((hp-0x7ff00000)\|lp)!=0)))
97	return (xp)/(xp);
98
99
100	if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */
101	if (((hx-hp)\|(lx-lp))==0) return zero*x;
102	x = fd_fabs(x);
103	p = fd_fabs(p);
104	if (hp<0x00200000) {
105	if(x+x>p) {
106	x-=p;
107	if(x+x>=p) x -= p;
108	}
109	} else {
110	p_half = 0.5*p;
111	if(x>p_half) {
112	x-=p;
113	if(x>=p_half) x -= p;
114	}
115	}
116	u.d = x;
117	__HI(u) ^= sx;
118	x = u.d;
119	return x;
120	}