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 * modfl(long double x, long 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
24
25 static const long double one = 1.0L;
26
27 long double
modfl(long double x,long double * iptr)28 modfl(long double x, long double *iptr)
29 {
30 int64_t i0,i1,jj0;
31 u_int64_t i;
32 GET_LDOUBLE_WORDS64(i0,i1,x);
33 jj0 = ((i0>>48)&0x7fff)-0x3fff; /* exponent of x */
34 if(jj0<48) { /* integer part in high x */
35 if(jj0<0) { /* |x|<1 */
36 /* *iptr = +-0 */
37 SET_LDOUBLE_WORDS64(*iptr,i0&0x8000000000000000ULL,0);
38 return x;
39 } else {
40 i = (0x0000ffffffffffffLL)>>jj0;
41 if(((i0&i)|i1)==0) { /* x is integral */
42 *iptr = x;
43 /* return +-0 */
44 SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
45 return x;
46 } else {
47 SET_LDOUBLE_WORDS64(*iptr,i0&(~i),0);
48 return x - *iptr;
49 }
50 }
51 } else if (jj0>111) { /* no fraction part */
52 *iptr = x*one;
53 /* We must handle NaNs separately. */
54 if (jj0 == 0x4000 && ((i0 & 0x0000ffffffffffffLL) | i1))
55 return x*one;
56 /* return +-0 */
57 SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
58 return x;
59 } else { /* fraction part in low x */
60 i = -1ULL>>(jj0-48);
61 if((i1&i)==0) { /* x is integral */
62 *iptr = x;
63 /* return +-0 */
64 SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
65 return x;
66 } else {
67 SET_LDOUBLE_WORDS64(*iptr,i0,i1&(~i));
68 return x - *iptr;
69 }
70 }
71 }
72
