src/fdlibm/e_fmod.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_fmod.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_fmod(x,y)
 * Return x mod y in exact arithmetic
 * Method: shift and subtract
 */

#include "fdlibm.h"

#ifdef __STDC__
static const double one = 1.0, Zero[] = {0.0, -0.0,};
#else
static double one = 1.0, Zero[] = {0.0, -0.0,};
#endif

#ifdef __STDC__
        double __ieee754_fmod(double x, double y)
#else
        double __ieee754_fmod(x,y)
        double x,y ;
#endif
{
        fd_twoints ux, uy;
        int n,hx,hy,hz,ix,iy,sx,i;
        unsigned lx,ly,lz;

        ux.d = x; uy.d = y;
        hx = __HI(ux);          /* high word of x */
        lx = __LO(ux);          /* low  word of x */
        hy = __HI(uy);          /* high word of y */
        ly = __LO(uy);          /* low  word of y */
        sx = hx&0x80000000;             /* sign of x */
        hx ^=sx;                /* |x| */
        hy &= 0x7fffffff;       /* |y| */

    /* purge off exception values */
        if((hy|ly)==0||(hx>=0x7ff00000)||       /* y=0,or x not finite */
          ((hy|((ly|-(int)ly)>>31))>0x7ff00000))        /* or y is NaN */
            return (x*y)/(x*y);
        if(hx<=hy) {
            if((hx<hy)||(lx<ly)) return x;      /* |x|<|y| return x */
            if(lx==ly) 
                return Zero[(unsigned)sx>>31];  /* |x|=|y| return x*0*/
        }

    /* determine ix = ilogb(x) */
        if(hx<0x00100000) {     /* subnormal x */
            if(hx==0) {
                for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
            } else {
                for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
            }
        } else ix = (hx>>20)-1023;

    /* determine iy = ilogb(y) */
        if(hy<0x00100000) {     /* subnormal y */
            if(hy==0) {
                for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
            } else {
                for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
            }
        } else iy = (hy>>20)-1023;

    /* set up {hx,lx}, {hy,ly} and align y to x */
        if(ix >= -1022) 
            hx = 0x00100000|(0x000fffff&hx);
        else {          /* subnormal x, shift x to normal */
            n = -1022-ix;
            if(n<=31) {
                hx = (hx<<n)|(lx>>(32-n));
                lx <<= n;
            } else {
                hx = lx<<(n-32);
                lx = 0;
            }
        }
        if(iy >= -1022) 
            hy = 0x00100000|(0x000fffff&hy);
        else {          /* subnormal y, shift y to normal */
            n = -1022-iy;
            if(n<=31) {
                hy = (hy<<n)|(ly>>(32-n));
                ly <<= n;
            } else {
                hy = ly<<(n-32);
                ly = 0;
            }
        }

    /* fix point fmod */
        n = ix - iy;
        while(n--) {
            hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
            if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
            else {
                if((hz|lz)==0)          /* return sign(x)*0 */
                    return Zero[(unsigned)sx>>31];
                hx = hz+hz+(lz>>31); lx = lz+lz;
            }
        }
        hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
        if(hz>=0) {hx=hz;lx=lz;}

    /* convert back to floating value and restore the sign */
        if((hx|lx)==0)                  /* return sign(x)*0 */
            return Zero[(unsigned)sx>>31];      
        while(hx<0x00100000) {          /* normalize x */
            hx = hx+hx+(lx>>31); lx = lx+lx;
            iy -= 1;
        }
        if(iy>= -1022) {        /* normalize output */
            hx = ((hx-0x00100000)|((iy+1023)<<20));
            ux.d = x;
            __HI(ux) = hx|sx;
            __LO(ux) = lx;
            x = ux.d;
        } else {                /* subnormal output */
            n = -1022 - iy;
            if(n<=20) {
                lx = (lx>>n)|((unsigned)hx<<(32-n));
                hx >>= n;
            } else if (n<=31) {
                lx = (hx<<(32-n))|(lx>>n); hx = sx;
            } else {
                lx = hx>>(n-32); hx = sx;
            }
            ux.d = x;
            __HI(ux) = hx|sx;
            __LO(ux) = lx;
            x = ux.d;
            x *= one;           /* create necessary signal */
        }
        return x;               /* exact output */
}
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_fmod.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	/*
53	* __ieee754_fmod(x,y)
54	* Return x mod y in exact arithmetic
55	* Method: shift and subtract
56	*/
57
58	#include "fdlibm.h"
59
60	#ifdef __STDC__
61	static const double one = 1.0, Zero[] = {0.0, -0.0,};
62	#else
63	static double one = 1.0, Zero[] = {0.0, -0.0,};
64	#endif
65
66	#ifdef __STDC__
67	double __ieee754_fmod(double x, double y)
68	#else
69	double __ieee754_fmod(x,y)
70	double x,y ;
71	#endif
72	{
73	fd_twoints ux, uy;
74	int n,hx,hy,hz,ix,iy,sx,i;
75	unsigned lx,ly,lz;
76
77	ux.d = x; uy.d = y;
78	hx = __HI(ux); /* high word of x */
79	lx = __LO(ux); /* low word of x */
80	hy = __HI(uy); /* high word of y */
81	ly = __LO(uy); /* low word of y */
82	sx = hx&0x80000000; /* sign of x */
83	hx ^=sx; /* \|x\| */
84	hy &= 0x7fffffff; /* \|y\| */
85
86	/* purge off exception values */
87	if((hy\|ly)==0\|\|(hx>=0x7ff00000)\|\| /* y=0,or x not finite */
88	((hy\|((ly\|-(int)ly)>>31))>0x7ff00000)) /* or y is NaN */
89	return (xy)/(xy);
90	if(hx<=hy) {
91	if((hx<hy)\|\|(lx<ly)) return x; /* \|x\|<\|y\| return x */
92	if(lx==ly)
93	return Zero[(unsigned)sx>>31]; /* \|x\|=\|y\| return x0/
94	}
95
96	/* determine ix = ilogb(x) */
97	if(hx<0x00100000) { /* subnormal x */
98	if(hx==0) {
99	for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
100	} else {
101	for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
102	}
103	} else ix = (hx>>20)-1023;
104
105	/* determine iy = ilogb(y) */
106	if(hy<0x00100000) { /* subnormal y */
107	if(hy==0) {
108	for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
109	} else {
110	for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
111	}
112	} else iy = (hy>>20)-1023;
113
114	/* set up {hx,lx}, {hy,ly} and align y to x */
115	if(ix >= -1022)
116	hx = 0x00100000\|(0x000fffff&hx);
117	else { /* subnormal x, shift x to normal */
118	n = -1022-ix;
119	if(n<=31) {
120	hx = (hx<<n)\|(lx>>(32-n));
121	lx <<= n;
122	} else {
123	hx = lx<<(n-32);
124	lx = 0;
125	}
126	}
127	if(iy >= -1022)
128	hy = 0x00100000\|(0x000fffff&hy);
129	else { /* subnormal y, shift y to normal */
130	n = -1022-iy;
131	if(n<=31) {
132	hy = (hy<<n)\|(ly>>(32-n));
133	ly <<= n;
134	} else {
135	hy = ly<<(n-32);
136	ly = 0;
137	}
138	}
139
140	/* fix point fmod */
141	n = ix - iy;
142	while(n--) {
143	hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
144	if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
145	else {
146	if((hz\|lz)==0) /* return sign(x)0 /
147	return Zero[(unsigned)sx>>31];
148	hx = hz+hz+(lz>>31); lx = lz+lz;
149	}
150	}
151	hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
152	if(hz>=0) {hx=hz;lx=lz;}
153
154	/* convert back to floating value and restore the sign */
155	if((hx\|lx)==0) /* return sign(x)0 /
156	return Zero[(unsigned)sx>>31];
157	while(hx<0x00100000) { /* normalize x */
158	hx = hx+hx+(lx>>31); lx = lx+lx;
159	iy -= 1;
160	}
161	if(iy>= -1022) { /* normalize output */
162	hx = ((hx-0x00100000)\|((iy+1023)<<20));
163	ux.d = x;
164	__HI(ux) = hx\|sx;
165	__LO(ux) = lx;
166	x = ux.d;
167	} else { /* subnormal output */
168	n = -1022 - iy;
169	if(n<=20) {
170	lx = (lx>>n)\|((unsigned)hx<<(32-n));
171	hx >>= n;
172	} else if (n<=31) {
173	lx = (hx<<(32-n))\|(lx>>n); hx = sx;
174	} else {
175	lx = hx>>(n-32); hx = sx;
176	}
177	ux.d = x;
178	__HI(ux) = hx\|sx;
179	__LO(ux) = lx;
180	x = ux.d;
181	x = one; / create necessary signal */
182	}
183	return x; /* exact output */
184	}