s_truncl.c revision 176243 
1/*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 *
11 * From: @(#)s_floor.c 5.1 93/09/24
12 */
13
14#ifndef lint
15static char rcsid[] = "$FreeBSD: head/lib/msun/src/s_truncl.c 176243 2008-02-13 16:56:52Z bde $";
16#endif
17
18/*
19 * truncl(x)
20 * Return x rounded toward 0 to integral value
21 * Method:
22 *	Bit twiddling.
23 * Exception:
24 *	Inexact flag raised if x not equal to truncl(x).
25 */
26
27#include <float.h>
28#include <math.h>
29#include <stdint.h>
30
31#include "fpmath.h"
32
33#ifdef LDBL_IMPLICIT_NBIT
34#define	MANH_SIZE	(LDBL_MANH_SIZE + 1)
35#else
36#define	MANH_SIZE	LDBL_MANH_SIZE
37#endif
38
39static const long double huge = 1.0e300;
40static const float zero[] = { 0.0, -0.0 };
41
42long double
43truncl(long double x)
44{
45	union IEEEl2bits u = { .e = x };
46	int e = u.bits.exp - LDBL_MAX_EXP + 1;
47
48	if (e < MANH_SIZE - 1) {
49		if (e < 0) {			/* raise inexact if x != 0 */
50			if (huge + x > 0.0)
51				u.e = zero[u.bits.sign];
52		} else {
53			uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
54			if (((u.bits.manh & m) | u.bits.manl) == 0)
55				return (x);	/* x is integral */
56			if (huge + x > 0.0) {	/* raise inexact flag */
57				u.bits.manh &= ~m;
58				u.bits.manl = 0;
59			}
60		}
61	} else if (e < LDBL_MANT_DIG - 1) {
62		uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
63		if ((u.bits.manl & m) == 0)
64			return (x);	/* x is integral */
65		if (huge + x > 0.0)		/* raise inexact flag */
66			u.bits.manl &= ~m;
67	}
68	return (u.e);
69}
70
71#if LDBL_MANT_DIG == 53
72__weak_reference(trunc, truncl);
73#endif
74