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 * trunc(x)
18 * Return x rounded toward 0 to integral value
19 * Method:
20 *	Bit twiddling.
21 * Exception:
22 *	Inexact flag raised if x not equal to trunc(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
33trunc(double x)
34{
35	int32_t i0,i1,j0;
36	u_int32_t i;
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) {/* |x|<1, so return 0*sign(x) */
42		    i0 &= 0x80000000U;
43		    i1 = 0;
44		}
45	    } else {
46		i = (0x000fffff)>>j0;
47		if(((i0&i)|i1)==0) return x; /* x is integral */
48		if(huge+x>0.0) {	/* raise inexact flag */
49		    i0 &= (~i); i1=0;
50		}
51	    }
52	} else if (j0>51) {
53	    if(j0==0x400) return x+x;	/* inf or NaN */
54	    else return x;		/* x is integral */
55	} else {
56	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
57	    if((i1&i)==0) return x;	/* x is integral */
58	    if(huge+x>0.0)		/* raise inexact flag */
59		i1 &= (~i);
60	}
61	INSERT_WORDS(x,i0,i1);
62	return x;
63}
64
65#if LDBL_MANT_DIG == 53
66__weak_reference(trunc, truncl);
67#endif
68