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_ceil.c 5.1 93/09/24
12 */
13
14#include <sys/cdefs.h>
15__FBSDID("$FreeBSD$");
16
17/*
18 * ceill(x)
19 * Return x rounded toward -inf to integral value
20 * Method:
21 *	Bit twiddling.
22 * Exception:
23 *	Inexact flag raised if x not equal to ceill(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#define	INC_MANH(u, c)	do {					\
35	uint64_t o = u.bits.manh;				\
36	u.bits.manh += (c);					\
37	if (u.bits.manh < o)					\
38		u.bits.exp++;					\
39} while (0)
40#else
41#define	MANH_SIZE	LDBL_MANH_SIZE
42#define	INC_MANH(u, c)	do {					\
43	uint64_t o = u.bits.manh;				\
44	u.bits.manh += (c);					\
45	if (u.bits.manh < o) {					\
46		u.bits.exp++;					\
47		u.bits.manh |= 1llu << (LDBL_MANH_SIZE - 1);	\
48	}							\
49} while (0)
50#endif
51
52static const long double huge = 1.0e300;
53
54long double
55ceill(long double x)
56{
57	union IEEEl2bits u = { .e = x };
58	int e = u.bits.exp - LDBL_MAX_EXP + 1;
59
60	if (e < MANH_SIZE - 1) {
61		if (e < 0) {			/* raise inexact if x != 0 */
62			if (huge + x > 0.0)
63				if (u.bits.exp > 0 ||
64				    (u.bits.manh | u.bits.manl) != 0)
65					u.e = u.bits.sign ? -0.0 : 1.0;
66		} else {
67			uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
68			if (((u.bits.manh & m) | u.bits.manl) == 0)
69				return (x);	/* x is integral */
70			if (!u.bits.sign) {
71#ifdef LDBL_IMPLICIT_NBIT
72				if (e == 0)
73					u.bits.exp++;
74				else
75#endif
76				INC_MANH(u, 1llu << (MANH_SIZE - e - 1));
77			}
78			if (huge + x > 0.0) {	/* raise inexact flag */
79				u.bits.manh &= ~m;
80				u.bits.manl = 0;
81			}
82		}
83	} else if (e < LDBL_MANT_DIG - 1) {
84		uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
85		if ((u.bits.manl & m) == 0)
86			return (x);	/* x is integral */
87		if (!u.bits.sign) {
88			if (e == MANH_SIZE - 1)
89				INC_MANH(u, 1);
90			else {
91				uint64_t o = u.bits.manl;
92				u.bits.manl += 1llu << (LDBL_MANT_DIG - e - 1);
93				if (u.bits.manl < o)	/* got a carry */
94					INC_MANH(u, 1);
95			}
96		}
97		if (huge + x > 0.0)		/* raise inexact flag */
98			u.bits.manl &= ~m;
99	}
100	return (u.e);
101}
102