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: src/lib/msun/src/s_trunc.c,v 1.1 2004/06/20 09:25:43 das Exp $"); */
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 "math.h"
26#include "math_private.h"
27
28static const double huge = 1.0e300;
29
30double
31trunc(double x)
32{
33	int32_t i0,i1,j0;
34	u_int32_t i,j;
35	EXTRACT_WORDS(i0,i1,x);
36	j0 = ((i0>>20)&0x7ff)-0x3ff;
37	if(j0<20) {
38	    if(j0<0) { 	/* raise inexact if x != 0 */
39		if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
40		    i0 &= 0x80000000U;
41		    i1 = 0;
42		}
43	    } else {
44		i = (0x000fffff)>>j0;
45		if(((i0&i)|i1)==0) return x; /* x is integral */
46		if(huge+x>0.0) {	/* raise inexact flag */
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		i1 &= (~i);
58	}
59	INSERT_WORDS(x,i0,i1);
60	return x;
61}
62