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
25 static const double one = 1.0;
26
modf(double x,double * iptr)27 double modf(double x, double *iptr)
28 {
29 int32_t i0,i1,_j0;
30 u_int32_t i;
31 EXTRACT_WORDS(i0,i1,x);
32 _j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
33 if(_j0<20) { /* integer part in high x */
34 if(_j0<0) { /* |x|<1 */
35 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */
36 return x;
37 } else {
38 i = (0x000fffff)>>_j0;
39 if(((i0&i)|i1)==0) { /* x is integral */
40 *iptr = x;
41 INSERT_WORDS(x,i0&0x80000000,0); /* return +-0 */
42 return x;
43 } else {
44 INSERT_WORDS(*iptr,i0&(~i),0);
45 return x - *iptr;
46 }
47 }
48 } else if (_j0>51) { /* no fraction part */
49 *iptr = x*one;
50 /* We must handle NaNs separately. */
51 if (_j0 == 0x400 && ((i0 & 0xfffff) | i1))
52 return x*one;
53 INSERT_WORDS(x,i0&0x80000000,0); /* return +-0 */
54 return x;
55 } else { /* fraction part in low x */
56 i = ((u_int32_t)(0xffffffff))>>(_j0-20);
57 if((i1&i)==0) { /* x is integral */
58 *iptr = x;
59 INSERT_WORDS(x,i0&0x80000000,0); /* return +-0 */
60 return x;
61 } else {
62 INSERT_WORDS(*iptr,i0,i1&(~i));
63 return x - *iptr;
64 }
65 }
66 }
67 libm_hidden_def(modf)
68