Atlas - s_floor.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 * floor(x)
15 * Return x rounded toward -inf to integral value
16 * Method:
17 *	Bit twiddling.
18 * Exception:
19 *	Inexact flag raised if x not equal to floor(x).
20 */
21
22/*#include <features.h>*/
23/* Prevent math.h from defining a colliding inline */
24#undef __USE_EXTERN_INLINES
25#include "math_libm.h"
26#include "math_private.h"
27
28static const double huge = 1.0e300;
29
30double floor(double x)
31{
32	int32_t i0,i1,j0;
33	u_int32_t i,j;
34	EXTRACT_WORDS(i0,i1,x);
35	j0 = ((i0>>20)&0x7ff)-0x3ff;
36	if(j0<20) {
37	    if(j0<0) { 	/* raise inexact if x != 0 */
38		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
39		    if(i0>=0) {i0=i1=0;}
40		    else if(((i0&0x7fffffff)|i1)!=0)
41			{ i0=0xbff00000;i1=0;}
42		}
43	    } else {
44		i = (0x000fffff)>>j0;
45		if(((i0&i)|i1)==0) return x; /* x is integral */
46		if(huge+x>0.0) {	/* raise inexact flag */
47		    if(i0<0) i0 += (0x00100000)>>j0;
48		    i0 &= (~i); i1=0;
49		}
50	    }
51	} else if (j0>51) {
52	    if(j0==0x400) return x+x;	/* inf or NaN */
53	    else return x;		/* x is integral */
54	} else {
55	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
56	    if((i1&i)==0) return x;	/* x is integral */
57	    if(huge+x>0.0) { 		/* raise inexact flag */
58		if(i0<0) {
59		    if(j0==20) i0+=1;
60		    else {
61			j = i1+(1<<(52-j0));
62			if(j<(u_int32_t)i1) i0 +=1 ; 	/* got a carry */
63			i1=j;
64		    }
65		}
66		i1 &= (~i);
67	    }
68	}
69	INSERT_WORDS(x,i0,i1);
70	return x;
71}
72libm_hidden_def(floor)
73
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