1 /*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 */
11
12 /* __ieee754_remainder(x,p)
13 * Return :
14 * returns x REM p = x - [x/p]*p as if in infinite
15 * precise arithmetic, where [x/p] is the (infinite bit)
16 * integer nearest x/p (in half way case choose the even one).
17 * Method :
18 * Based on fmod() return x-[x/p]chopped*p exactlp.
19 */
20
21 #include "math.h"
22 #include "math_private.h"
23
24 static const double zero = 0.0;
25
__ieee754_remainder(double x,double p)26 double __ieee754_remainder(double x, double p)
27 {
28 int32_t hx,hp;
29 u_int32_t sx,lx,lp;
30 double p_half;
31
32 EXTRACT_WORDS(hx,lx,x);
33 EXTRACT_WORDS(hp,lp,p);
34 sx = hx&0x80000000;
35 hp &= 0x7fffffff;
36 hx &= 0x7fffffff;
37
38 /* purge off exception values */
39 if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */
40 if((hx>=0x7ff00000)|| /* x not finite */
41 ((hp>=0x7ff00000)&& /* p is NaN */
42 (((hp-0x7ff00000)|lp)!=0)))
43 return (x*p)/(x*p);
44
45
46 if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */
47 if (((hx-hp)|(lx-lp))==0) return zero*x;
48 x = fabs(x);
49 p = fabs(p);
50 if (hp<0x00200000) {
51 if(x+x>p) {
52 x-=p;
53 if(x+x>=p) x -= p;
54 }
55 } else {
56 p_half = 0.5*p;
57 if(x>p_half) {
58 x-=p;
59 if(x>=p_half) x -= p;
60 }
61 }
62 GET_HIGH_WORD(hx,x);
63 SET_HIGH_WORD(x,hx^sx);
64 return x;
65 }
66
67 /*
68 * wrapper remainder(x,p)
69 */
70 #ifndef _IEEE_LIBM
remainder(double x,double y)71 double remainder(double x, double y)
72 {
73 double z = __ieee754_remainder(x, y);
74 if (_LIB_VERSION == _IEEE_ || isnan(y))
75 return z;
76 if (y == 0.0)
77 return __kernel_standard(x, y, 28); /* remainder(x,0) */
78 return z;
79 }
80 strong_alias(remainder, drem)
81 #else
82 strong_alias(__ieee754_remainder, remainder)
83 strong_alias(__ieee754_remainder, drem)
84 #endif
85 libm_hidden_def(remainder)
86