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 0
15__FBSDID("$FreeBSD: src/lib/msun/src/s_trunc.c,v 1.1 2004/06/20 09:25:43 das Exp $");
16#endif
17#if defined(LIBM_SCCS) && !defined(lint)
18__RCSID("$NetBSD: s_trunc.c,v 1.3 2008/04/25 22:21:53 christos Exp $");
19#endif
20
21/*
22 * trunc(x)
23 * Return x rounded toward 0 to integral value
24 * Method:
25 *	Bit twiddling.
26 * Exception:
27 *	Inexact flag raised if x not equal to trunc(x).
28 */
29
30#include "math.h"
31#include "math_private.h"
32
33#ifndef __HAVE_LONG_DOUBLE
34__strong_alias(_truncl, trunc)
35__weak_alias(truncl, trunc)
36#endif
37
38static const double huge = 1.0e300;
39
40double
41trunc(double x)
42{
43	int32_t i0,i1,jj0;
44	uint32_t i;
45	EXTRACT_WORDS(i0,i1,x);
46	jj0 = ((i0>>20)&0x7ff)-0x3ff;
47	if(jj0<20) {
48	    if(jj0<0) { 	/* raise inexact if x != 0 */
49		if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
50		    i0 &= 0x80000000U;
51		    i1 = 0;
52		}
53	    } else {
54		i = (0x000fffff)>>jj0;
55		if(((i0&i)|i1)==0) return x; /* x is integral */
56		if(huge+x>0.0) {	/* raise inexact flag */
57		    i0 &= (~i); i1=0;
58		}
59	    }
60	} else if (jj0>51) {
61	    if(jj0==0x400) return x+x;	/* inf or NaN */
62	    else return x;		/* x is integral */
63	} else {
64	    i = ((u_int32_t)(0xffffffff))>>(jj0-20);
65	    if((i1&i)==0) return x;	/* x is integral */
66	    if(huge+x>0.0)		/* raise inexact flag */
67		i1 &= (~i);
68	}
69	INSERT_WORDS(x,i0,i1);
70	return x;
71}
72