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#include <sys/cdefs.h>
15__FBSDID("$FreeBSD$");
16
17/*
18 * truncl(x)
19 * Return x rounded toward 0 to integral value
20 * Method:
21 *	Bit twiddling.
22 * Exception:
23 *	Inexact flag raised if x not equal to truncl(x).
24 */
25
26#include <float.h>
27#include <math.h>
28#include <stdint.h>
29
30#include "fpmath.h"
31
32#ifdef LDBL_IMPLICIT_NBIT
33#define	MANH_SIZE	(LDBL_MANH_SIZE + 1)
34#else
35#define	MANH_SIZE	LDBL_MANH_SIZE
36#endif
37
38static const long double huge = 1.0e300;
39static const float zero[] = { 0.0, -0.0 };
40
41long double
42truncl(long double x)
43{
44	union IEEEl2bits u = { .e = x };
45	int e = u.bits.exp - LDBL_MAX_EXP + 1;
46
47	if (e < MANH_SIZE - 1) {
48		if (e < 0) {			/* raise inexact if x != 0 */
49			if (huge + x > 0.0)
50				u.e = zero[u.bits.sign];
51		} else {
52			uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
53			if (((u.bits.manh & m) | u.bits.manl) == 0)
54				return (x);	/* x is integral */
55			if (huge + x > 0.0) {	/* raise inexact flag */
56				u.bits.manh &= ~m;
57				u.bits.manl = 0;
58			}
59		}
60	} else if (e < LDBL_MANT_DIG - 1) {
61		uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
62		if ((u.bits.manl & m) == 0)
63			return (x);	/* x is integral */
64		if (huge + x > 0.0)		/* raise inexact flag */
65			u.bits.manl &= ~m;
66	}
67	return (u.e);
68}
69