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 #ifndef lint
15 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_ceill.c,v 1.4 2005/04/28 19:45:55 stefanf Exp $";
16 #endif
17
18 /*
19 * ceill(x)
20 * Return x rounded toward -inf to integral value
21 * Method:
22 * Bit twiddling.
23 * Exception:
24 * Inexact flag raised if x not equal to ceill(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 #define INC_MANH(u, c) do { \
36 uint64_t o = u.bits.manh; \
37 u.bits.manh += (c); \
38 if (u.bits.manh < o) \
39 u.bits.exp++; \
40 } while (0)
41 #else
42 #define MANH_SIZE LDBL_MANH_SIZE
43 #define INC_MANH(u, c) do { \
44 uint64_t o = u.bits.manh; \
45 u.bits.manh += (c); \
46 if (u.bits.manh < o) { \
47 u.bits.exp++; \
48 u.bits.manh |= 1llu << (LDBL_MANH_SIZE - 1); \
49 } \
50 } while (0)
51 #endif
52
53 static const long double huge = 1.0e300;
54
55 long double
ceill(long double x)56 ceill(long double x)
57 {
58 union IEEEl2bits u = { .e = x };
59 int e = u.bits.exp - LDBL_MAX_EXP + 1;
60
61 if (e < MANH_SIZE - 1) {
62 if (e < 0) { /* raise inexact if x != 0 */
63 if (huge + x > 0.0)
64 if (u.bits.exp > 0 ||
65 (u.bits.manh | u.bits.manl) != 0)
66 u.e = u.bits.sign ? 0.0 : 1.0;
67 } else {
68 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
69 if (((u.bits.manh & m) | u.bits.manl) == 0)
70 return (x); /* x is integral */
71 if (!u.bits.sign) {
72 #ifdef LDBL_IMPLICIT_NBIT
73 if (e == 0)
74 u.bits.exp++;
75 else
76 #endif
77 INC_MANH(u, 1llu << (MANH_SIZE - e - 1));
78 }
79 if (huge + x > 0.0) { /* raise inexact flag */
80 u.bits.manh &= ~m;
81 u.bits.manl = 0;
82 }
83 }
84 } else if (e < LDBL_MANT_DIG - 1) {
85 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
86 if ((u.bits.manl & m) == 0)
87 return (x); /* x is integral */
88 if (!u.bits.sign) {
89 if (e == MANH_SIZE - 1)
90 INC_MANH(u, 1);
91 else {
92 uint64_t o = u.bits.manl;
93 u.bits.manl += 1llu << (LDBL_MANT_DIG - e - 1);
94 if (u.bits.manl < o) /* got a carry */
95 INC_MANH(u, 1);
96 }
97 }
98 if (huge + x > 0.0) /* raise inexact flag */
99 u.bits.manl &= ~m;
100 }
101 return (u.e);
102 }
103