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 /*
13 * modf(double x, double *iptr)
14 * return fraction part of x, and return x's integral part in *iptr.
15 * Method:
16 * Bit twiddling.
17 *
18 * Exception:
19 * No exception.
20 */
21
22 #include <math.h>
23 #include <math_private.h>
24 #include <libm-alias-double.h>
25 #include <stdint.h>
26
27 static const double one = 1.0;
28
29 double
__modf(double x,double * iptr)30 __modf(double x, double *iptr)
31 {
32 int64_t i0;
33 int32_t j0;
34 EXTRACT_WORDS64(i0,x);
35 j0 = ((i0>>52)&0x7ff)-0x3ff; /* exponent of x */
36 if(j0<52) { /* integer part in x */
37 if(j0<0) { /* |x|<1 */
38 /* *iptr = +-0 */
39 INSERT_WORDS64(*iptr,i0&UINT64_C(0x8000000000000000));
40 return x;
41 } else {
42 uint64_t i = UINT64_C(0x000fffffffffffff)>>j0;
43 if((i0&i)==0) { /* x is integral */
44 *iptr = x;
45 /* return +-0 */
46 INSERT_WORDS64(x,i0&UINT64_C(0x8000000000000000));
47 return x;
48 } else {
49 INSERT_WORDS64(*iptr,i0&(~i));
50 return x - *iptr;
51 }
52 }
53 } else { /* no fraction part */
54 *iptr = x*one;
55 /* We must handle NaNs separately. */
56 if (j0 == 0x400 && (i0 & UINT64_C(0xfffffffffffff)))
57 return x*one;
58 INSERT_WORDS64(x,i0&UINT64_C(0x8000000000000000)); /* return +-0 */
59 return x;
60 }
61 }
62 #ifndef __modf
63 libm_alias_double (__modf, modf)
64 #endif
65