Update.
[glibc.git] / sysdeps / libm-ieee754 / e_remainder.c
blob6418081182ad67f06381be24c729c90d49b726b6
1 /* @(#)e_remainder.c 5.1 93/09/24 */
2 /*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
13 #if defined(LIBM_SCCS) && !defined(lint)
14 static char rcsid[] = "$NetBSD: e_remainder.c,v 1.8 1995/05/10 20:46:05 jtc Exp $";
15 #endif
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.
26 #include "math.h"
27 #include "math_private.h"
29 #ifdef __STDC__
30 static const double zero = 0.0;
31 #else
32 static double zero = 0.0;
33 #endif
36 #ifdef __STDC__
37 double __ieee754_remainder(double x, double p)
38 #else
39 double __ieee754_remainder(x,p)
40 double x,p;
41 #endif
43 int32_t hx,hp;
44 u_int32_t sx,lx,lp;
45 double p_half;
47 EXTRACT_WORDS(hx,lx,x);
48 EXTRACT_WORDS(hp,lp,p);
49 sx = hx&0x80000000;
50 hp &= 0x7fffffff;
51 hx &= 0x7fffffff;
53 /* purge off exception values */
54 if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */
55 if((hx>=0x7ff00000)|| /* x not finite */
56 ((hp>=0x7ff00000)&& /* p is NaN */
57 (((hp-0x7ff00000)|lp)!=0)))
58 return (x*p)/(x*p);
61 if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */
62 if (((hx-hp)|(lx-lp))==0) return zero*x;
63 x = fabs(x);
64 p = fabs(p);
65 if (hp<0x00200000) {
66 if(x+x>p) {
67 x-=p;
68 if(x+x>=p) x -= p;
70 } else {
71 p_half = 0.5*p;
72 if(x>p_half) {
73 x-=p;
74 if(x>=p_half) x -= p;
77 GET_HIGH_WORD(hx,x);
78 SET_HIGH_WORD(x,hx^sx);
79 return x;