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
31static const double zero = 0.0;
32
33
34double
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