Atlas - s_modf.c
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[FILE BEGIN]
1#include "SDL_internal.h"
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 * modf(double x, 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#include "math_libm.h"
24#include "math_private.h"
25
26static const double one = 1.0;
27
28double modf(double x, double *iptr)
29{
30	int32_t i0,i1,_j0;
31	u_int32_t i;
32	EXTRACT_WORDS(i0,i1,x);
33	_j0 = ((i0>>20)&0x7ff)-0x3ff;	/* exponent of x */
34	if(_j0<20) {			/* integer part in high x */
35	    if(_j0<0) {			/* |x|<1 */
36	        INSERT_WORDS(*iptr,i0&0x80000000,0);	/* *iptr = +-0 */
37		return x;
38	    } else {
39		i = (0x000fffff)>>_j0;
40		if(((i0&i)|i1)==0) {		/* x is integral */
41		    *iptr = x;
42		    INSERT_WORDS(x,i0&0x80000000,0);	/* return +-0 */
43		    return x;
44		} else {
45		    INSERT_WORDS(*iptr,i0&(~i),0);
46		    return x - *iptr;
47		}
48	    }
49	} else if (_j0>51) {		/* no fraction part */
50	    *iptr = x*one;
51	    /* We must handle NaNs separately.  */
52	    if (_j0 == 0x400 && ((i0 & 0xfffff) | i1))
53	      return x*one;
54	    INSERT_WORDS(x,i0&0x80000000,0);	/* return +-0 */
55	    return x;
56	} else {			/* fraction part in low x */
57	    i = ((u_int32_t)(0xffffffff))>>(_j0-20);
58	    if((i1&i)==0) { 		/* x is integral */
59		*iptr = x;
60		INSERT_WORDS(x,i0&0x80000000,0);	/* return +-0 */
61		return x;
62	    } else {
63	        INSERT_WORDS(*iptr,i0,i1&(~i));
64		return x - *iptr;
65	    }
66	}
67}
68libm_hidden_def(modf)
69
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