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 #include <sys/cdefs.h>
14 #if defined(LIBM_SCCS) && !defined(lint)
15 __RCSID("$NetBSD: s_modf.c,v 1.15 2014/06/16 12:54:43 joerg Exp $");
16 #endif
17
18 /*
19 * modf(double x, double *iptr)
20 * return fraction part of x, and return x's integral part in *iptr.
21 * Method:
22 * Bit twiddling.
23 *
24 * Exception:
25 * No exception.
26 */
27
28 #include "math.h"
29 #include "math_private.h"
30
31 static const double one = 1.0;
32
33 #ifndef __HAVE_LONG_DOUBLE
__strong_alias(_modfl,modf)34 __strong_alias(_modfl, modf)
35 __weak_alias(modfl, modf)
36 #endif
37
38 double
39 modf(double x, double *iptr)
40 {
41 int32_t i0,i1,jj0;
42 u_int32_t i;
43 EXTRACT_WORDS(i0,i1,x);
44 jj0 = (((uint32_t)i0>>20)&0x7ff)-0x3ff; /* exponent of x */
45 if(jj0<20) { /* integer part in high x */
46 if(jj0<0) { /* |x|<1 */
47 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */
48 return x;
49 } else {
50 i = (0x000fffff)>>jj0;
51 if(((i0&i)|i1)==0) { /* x is integral */
52 u_int32_t high;
53 *iptr = x;
54 GET_HIGH_WORD(high,x);
55 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
56 return x;
57 } else {
58 INSERT_WORDS(*iptr,i0&(~i),0);
59 return x - *iptr;
60 }
61 }
62 } else if (jj0>51) { /* no fraction part */
63 u_int32_t high;
64 *iptr = x*one;
65 if (jj0 == 0x400) /* +-inf or NaN */
66 return 0.0 / x; /* +-0 or NaN */
67 GET_HIGH_WORD(high,x);
68 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
69 return x;
70 } else { /* fraction part in low x */
71 i = ((u_int32_t)(0xffffffff))>>(jj0-20);
72 if((i1&i)==0) { /* x is integral */
73 u_int32_t high;
74 *iptr = x;
75 GET_HIGH_WORD(high,x);
76 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
77 return x;
78 } else {
79 INSERT_WORDS(*iptr,i0,i1&(~i));
80 return x - *iptr;
81 }
82 }
83 }
84