| 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 | |