1/* @(#)s_floor.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_floor.c,v 1.13 2009/02/16 01:27:36 lukem Exp $");
16#endif
17
18/*
19 * floor(x)
20 * Return x rounded toward -inf to integral value
21 * Method:
22 *	Bit twiddling.
23 * Exception:
24 *	Inexact flag raised if x not equal to floor(x).
25 */
26
27#include "math.h"
28#include "math_private.h"
29
30#ifndef __HAVE_LONG_DOUBLE
31__strong_alias(_floorl, floor)
32__weak_alias(floorl, floor)
33#endif
34
35static const double huge = 1.0e300;
36
37double
38floor(double x)
39{
40	int32_t i0,i1,jj0;
41	u_int32_t i,j;
42	EXTRACT_WORDS(i0,i1,x);
43	jj0 = ((i0>>20)&0x7ff)-0x3ff;
44	if(jj0<20) {
45	    if(jj0<0) { 	/* raise inexact if x != 0 */
46		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
47		    if(i0>=0) {i0=i1=0;}
48		    else if(((i0&0x7fffffff)|i1)!=0)
49			{ i0=0xbff00000;i1=0;}
50		}
51	    } else {
52		i = (0x000fffff)>>jj0;
53		if(((i0&i)|i1)==0) return x; /* x is integral */
54		if(huge+x>0.0) {	/* raise inexact flag */
55		    if(i0<0) i0 += (0x00100000)>>jj0;
56		    i0 &= (~i); i1=0;
57		}
58	    }
59	} else if (jj0>51) {
60	    if(jj0==0x400) return x+x;	/* inf or NaN */
61	    else return x;		/* x is integral */
62	} else {
63	    i = ((u_int32_t)(0xffffffff))>>(jj0-20);
64	    if((i1&i)==0) return x;	/* x is integral */
65	    if(huge+x>0.0) { 		/* raise inexact flag */
66		if(i0<0) {
67		    if(jj0==20) i0+=1;
68		    else {
69			j = i1+(1<<(52-jj0));
70			if(j<(u_int32_t)i1) i0 +=1 ; 	/* got a carry */
71			i1=j;
72		    }
73		}
74		i1 &= (~i);
75	    }
76	}
77	INSERT_WORDS(x,i0,i1);
78	return x;
79}
80