1 /* @(#)s_modf.c 5.1 93/09/24 */
2 /*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
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 * ====================================================
11 */
12
13 /*
14 * modf(double x, double *iptr)
15 * return fraction part of x, and return x's integral part in *iptr.
16 * Method:
17 * Bit twiddling.
18 *
19 * Exception:
20 * No exception.
21 */
22
23 #include "math.h"
24 #include "math_private.h"
25
26 static const double one = 1.0;
27
28 double
modf(double x,double * iptr)29 modf(double x, double *iptr)
30 {
31 int32_t i0,i1,j0;
32 u_int32_t i;
33 EXTRACT_WORDS(i0,i1,x);
34 j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
35 if(j0<20) { /* integer part in high x */
36 if(j0<0) { /* |x|<1 */
37 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */
38 return x;
39 } else {
40 i = (0x000fffff)>>j0;
41 if(((i0&i)|i1)==0) { /* x is integral */
42 u_int32_t high;
43 *iptr = x;
44 GET_HIGH_WORD(high,x);
45 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
46 return x;
47 } else {
48 INSERT_WORDS(*iptr,i0&(~i),0);
49 return x - *iptr;
50 }
51 }
52 } else if (j0>51) { /* no fraction part */
53 u_int32_t high;
54 if (j0 == 0x400) { /* inf/NaN */
55 *iptr = x;
56 return 0.0 / x;
57 }
58 *iptr = x*one;
59 GET_HIGH_WORD(high,x);
60 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
61 return x;
62 } else { /* fraction part in low x */
63 i = ((u_int32_t)(0xffffffff))>>(j0-20);
64 if((i1&i)==0) { /* x is integral */
65 u_int32_t high;
66 *iptr = x;
67 GET_HIGH_WORD(high,x);
68 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
69 return x;
70 } else {
71 INSERT_WORDS(*iptr,i0,i1&(~i));
72 return x - *iptr;
73 }
74 }
75 }
76