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__FBSDID("$FreeBSD$");
15
16/*
17 * floor(x)
18 * Return x rounded toward -inf to integral value
19 * Method:
20 *	Bit twiddling.
21 * Exception:
22 *	Inexact flag raised if x not equal to floor(x).
23 */
24
25#include <float.h>
26
27#include "math.h"
28#include "math_private.h"
29
30static const double huge = 1.0e300;
31
32double
33floor(double x)
34{
35	int32_t i0,i1,j0;
36	u_int32_t i,j;
37	EXTRACT_WORDS(i0,i1,x);
38	j0 = ((i0>>20)&0x7ff)-0x3ff;
39	if(j0<20) {
40	    if(j0<0) { 	/* raise inexact if x != 0 */
41		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
42		    if(i0>=0) {i0=i1=0;}
43		    else if(((i0&0x7fffffff)|i1)!=0)
44			{ i0=0xbff00000;i1=0;}
45		}
46	    } else {
47		i = (0x000fffff)>>j0;
48		if(((i0&i)|i1)==0) return x; /* x is integral */
49		if(huge+x>0.0) {	/* raise inexact flag */
50		    if(i0<0) i0 += (0x00100000)>>j0;
51		    i0 &= (~i); i1=0;
52		}
53	    }
54	} else if (j0>51) {
55	    if(j0==0x400) return x+x;	/* inf or NaN */
56	    else return x;		/* x is integral */
57	} else {
58	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
59	    if((i1&i)==0) return x;	/* x is integral */
60	    if(huge+x>0.0) { 		/* raise inexact flag */
61		if(i0<0) {
62		    if(j0==20) i0+=1;
63		    else {
64			j = i1+(1<<(52-j0));
65			if(j<i1) i0 +=1 ; 	/* got a carry */
66			i1=j;
67		    }
68		}
69		i1 &= (~i);
70	    }
71	}
72	INSERT_WORDS(x,i0,i1);
73	return x;
74}
75
76#if LDBL_MANT_DIG == 53
77__weak_reference(floor, floorl);
78#endif
79