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#if defined(LIBM_SCCS) && !defined(lint)
14static char rcsid[] = "$NetBSD: s_modf.c,v 1.8 1995/05/10 20:47:55 jtc 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#ifdef __STDC__
31static const double one = 1.0;
32#else
33static double one = 1.0;
34#endif
35
36#ifdef __STDC__
37	double __modf(double x, double *iptr)
38#else
39	double __modf(x, iptr)
40	double x,*iptr;
41#endif
42{
43	int32_t i0,i1,j0;
44	u_int32_t i;
45	EXTRACT_WORDS(i0,i1,x);
46	j0 = ((i0>>20)&0x7ff)-0x3ff;	/* exponent of x */
47	if(j0<20) {			/* integer part in high x */
48	    if(j0<0) {			/* |x|<1 */
49	        INSERT_WORDS(*iptr,i0&0x80000000,0);	/* *iptr = +-0 */
50		return x;
51	    } else {
52		i = (0x000fffff)>>j0;
53		if(((i0&i)|i1)==0) {		/* x is integral */
54		    *iptr = x;
55		    INSERT_WORDS(x,i0&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 (j0>51) {		/* no fraction part */
63	    *iptr = x*one;
64	    /* We must handle NaNs separately.  */
65	    if (j0 == 0x400 && ((i0 & 0xfffff) | i1))
66	      return x*one;
67	    INSERT_WORDS(x,i0&0x80000000,0);	/* return +-0 */
68	    return x;
69	} else {			/* fraction part in low x */
70	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
71	    if((i1&i)==0) { 		/* x is integral */
72		*iptr = x;
73		INSERT_WORDS(x,i0&0x80000000,0);	/* return +-0 */
74		return x;
75	    } else {
76	        INSERT_WORDS(*iptr,i0,i1&(~i));
77		return x - *iptr;
78	    }
79	}
80}
81weak_alias (__modf, modf)
82#ifdef NO_LONG_DOUBLE
83strong_alias (__modf, __modfl)
84weak_alias (__modf, modfl)
85#endif
86