Atlas - s_floor.c
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1/*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 */
11
12/*
13 * floor(x)
14 * Return x rounded toward -inf to integral value
15 * Method:
16 *	Bit twiddling.
17 * Exception:
18 *	Inexact flag raised if x not equal to floor(x).
19 */
20
21/*#include <features.h>*/
22/* Prevent math.h from defining a colliding inline */
23#undef __USE_EXTERN_INLINES
24#include "math_libm.h"
25#include "math_private.h"
26
27static const double huge = 1.0e300;
28
29double floor(double x)
30{
31	int32_t i0,i1,j0;
32	u_int32_t i,j;
33	EXTRACT_WORDS(i0,i1,x);
34	j0 = ((i0>>20)&0x7ff)-0x3ff;
35	if(j0<20) {
36	    if(j0<0) { 	/* raise inexact if x != 0 */
37		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
38		    if(i0>=0) {i0=i1=0;}
39		    else if(((i0&0x7fffffff)|i1)!=0)
40			{ i0=0xbff00000;i1=0;}
41		}
42	    } else {
43		i = (0x000fffff)>>j0;
44		if(((i0&i)|i1)==0) return x; /* x is integral */
45		if(huge+x>0.0) {	/* raise inexact flag */
46		    if(i0<0) i0 += (0x00100000)>>j0;
47		    i0 &= (~i); i1=0;
48		}
49	    }
50	} else if (j0>51) {
51	    if(j0==0x400) return x+x;	/* inf or NaN */
52	    else return x;		/* x is integral */
53	} else {
54	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
55	    if((i1&i)==0) return x;	/* x is integral */
56	    if(huge+x>0.0) { 		/* raise inexact flag */
57		if(i0<0) {
58		    if(j0==20) i0+=1;
59		    else {
60			j = i1+(1<<(52-j0));
61			if(j<(u_int32_t)i1) i0 +=1 ; 	/* got a carry */
62			i1=j;
63		    }
64		}
65		i1 &= (~i);
66	    }
67	}
68	INSERT_WORDS(x,i0,i1);
69	return x;
70}
71libm_hidden_def(floor)
72
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