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/* __ieee754_remainder(x,p)
15 * Return :
16 * 	returns  x REM p  =  x - [x/p]*p as if in infinite
17 * 	precise arithmetic, where [x/p] is the (infinite bit)
18 *	integer nearest x/p (in half way case choose the even one).
19 * Method :
20 *	Based on ieee_fmod() return x-[x/p]chopped*p exactlp.
21 */
22
23#include "fdlibm.h"
24
25#ifdef __STDC__
26static const double zero = 0.0;
27#else
28static double zero = 0.0;
29#endif
30
31
32#ifdef __STDC__
33	double __ieee754_remainder(double x, double p)
34#else
35	double __ieee754_remainder(x,p)
36	double x,p;
37#endif
38{
39	int hx,hp;
40	unsigned sx,lx,lp;
41	double p_half;
42
43	hx = __HI(x);		/* high word of x */
44	lx = __LO(x);		/* low  word of x */
45	hp = __HI(p);		/* high word of p */
46	lp = __LO(p);		/* low  word of p */
47	sx = hx&0x80000000;
48	hp &= 0x7fffffff;
49	hx &= 0x7fffffff;
50
51    /* purge off exception values */
52	if((hp|lp)==0) return (x*p)/(x*p); 	/* p = 0 */
53	if((hx>=0x7ff00000)||			/* x not finite */
54	  ((hp>=0x7ff00000)&&			/* p is NaN */
55	  (((hp-0x7ff00000)|lp)!=0)))
56	    return (x*p)/(x*p);
57
58
59	if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p);	/* now x < 2p */
60	if (((hx-hp)|(lx-lp))==0) return zero*x;
61	x  = ieee_fabs(x);
62	p  = ieee_fabs(p);
63	if (hp<0x00200000) {
64	    if(x+x>p) {
65		x-=p;
66		if(x+x>=p) x -= p;
67	    }
68	} else {
69	    p_half = 0.5*p;
70	    if(x>p_half) {
71		x-=p;
72		if(x>=p_half) x -= p;
73	    }
74	}
75	__HI(x) ^= sx;
76	return x;
77}
78