1 /* $NetBSD: log2.h,v 1.5 2014/08/06 14:05:08 riastradh Exp $ */
2
3 /*-
4 * Copyright (c) 2013 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Taylor R. Campbell.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #ifndef _LINUX_LOG2_H_
33 #define _LINUX_LOG2_H_
34
35 #include <sys/types.h>
36 #include <sys/bitops.h>
37
38 #include <machine/limits.h>
39
40 static inline bool
is_power_of_2(unsigned long x)41 is_power_of_2(unsigned long x)
42 {
43 return ((x != 0) && (((x - 1) & x) == 0));
44 }
45
46 static inline unsigned long
roundup_pow_of_two(unsigned long n)47 roundup_pow_of_two(unsigned long n)
48 {
49 unsigned i;
50
51 if (n == 0)
52 return 1;
53
54 n -= 1;
55 for (i = 1; i < CHAR_BIT * sizeof n; i <<= 1)
56 n |= (n >> i);
57
58 return (n + 1);
59 }
60
61 static inline unsigned long
rounddown_pow_of_two(unsigned long n)62 rounddown_pow_of_two(unsigned long n)
63 {
64
65 /* XXX fls64 is not fls_ulong, but it'll do for now. */
66 return (1UL << (fls64(n) - 1));
67 }
68
69 static inline unsigned
order_base_2(unsigned long n)70 order_base_2(unsigned long n)
71 {
72
73 return ilog2(roundup_pow_of_two(n));
74 }
75
76 #endif /* _LINUX_LOG2_H_ */
77