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