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---
s_modf.c (1917B)
---
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 #ifndef lint
14 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_modf.c,v 1.7 2002/05/28 18:15:04 alfred Exp $";
15 #endif
16
17 /*
18 * modf(double x, double *iptr)
19 * return fraction part of x, and return x's integral part in *iptr.
20 * Method:
21 * Bit twiddling.
22 *
23 * Exception:
24 * No exception.
25 */
26
27 #include "math.h"
28 #include "math_private.h"
29
30 static const double one = 1.0;
31
32 double
33 modf(double x, double *iptr)
34 {
35 int32_t i0,i1,j0;
36 u_int32_t i;
37 EXTRACT_WORDS(i0,i1,x);
38 j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
39 if(j0<20) { /* integer part in high x */
40 if(j0<0) { /* |x|<1 */
41 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */
42 return x;
43 } else {
44 i = (0x000fffff)>>j0;
45 if(((i0&i)|i1)==0) { /* x is integral */
46 u_int32_t high;
47 *iptr = x;
48 GET_HIGH_WORD(high,x);
49 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
50 return x;
51 } else {
52 INSERT_WORDS(*iptr,i0&(~i),0);
53 return x - *iptr;
54 }
55 }
56 } else if (j0>51) { /* no fraction part */
57 u_int32_t high;
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 }