1 
2 /* @(#)e_remainder.c 1.3 95/01/18 */
3 /*
4  * ====================================================
5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6  *
7  * Developed at SunSoft, a Sun Microsystems, Inc. business.
8  * Permission to use, copy, modify, and distribute this
9  * software is freely granted, provided that this notice
10  * is preserved.
11  * ====================================================
12  */
13 
14 #include <sys/cdefs.h>
15 __FBSDID("$FreeBSD$");
16 
17 /* __ieee754_remainder(x,p)
18  * Return :
19  * 	returns  x REM p  =  x - [x/p]*p as if in infinite
20  * 	precise arithmetic, where [x/p] is the (infinite bit)
21  *	integer nearest x/p (in half way case choose the even one).
22  * Method :
23  *	Based on fmod() return x-[x/p]chopped*p exactlp.
24  */
25 
26 #include <float.h>
27 
28 #include "math.h"
29 #include "math_private.h"
30 
31 static const double zero = 0.0;
32 
33 
34 double
__ieee754_remainder(double x,double p)35 __ieee754_remainder(double x, double p)
36 {
37 	int32_t hx,hp;
38 	u_int32_t sx,lx,lp;
39 	double p_half;
40 
41 	EXTRACT_WORDS(hx,lx,x);
42 	EXTRACT_WORDS(hp,lp,p);
43 	sx = hx&0x80000000;
44 	hp &= 0x7fffffff;
45 	hx &= 0x7fffffff;
46 
47     /* purge off exception values */
48 	if((hp|lp)==0) return (x*p)/(x*p); 	/* p = 0 */
49 	if((hx>=0x7ff00000)||			/* x not finite */
50 	  ((hp>=0x7ff00000)&&			/* p is NaN */
51 	  (((hp-0x7ff00000)|lp)!=0)))
52 	    return ((long double)x*p)/((long double)x*p);
53 
54 
55 	if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p);	/* now x < 2p */
56 	if (((hx-hp)|(lx-lp))==0) return zero*x;
57 	x  = fabs(x);
58 	p  = fabs(p);
59 	if (hp<0x00200000) {
60 	    if(x+x>p) {
61 		x-=p;
62 		if(x+x>=p) x -= p;
63 	    }
64 	} else {
65 	    p_half = 0.5*p;
66 	    if(x>p_half) {
67 		x-=p;
68 		if(x>=p_half) x -= p;
69 	    }
70 	}
71 	GET_HIGH_WORD(hx,x);
72 	if ((hx&0x7fffffff)==0) hx = 0;
73 	SET_HIGH_WORD(x,hx^sx);
74 	return x;
75 }
76 
77 #if LDBL_MANT_DIG == 53
78 __weak_reference(remainder, remainderl);
79 #endif
80