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 |
41 | is_power_of_2(unsigned long x) |
42 | { |
43 | return ((x != 0) && (((x - 1) & x) == 0)); |
44 | } |
45 | |
46 | static inline unsigned long |
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 |
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 |
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 | |