log2.h revision 1.1.6.2
1 1.1.6.2 martin /* $NetBSD: log2.h,v 1.1.6.2 2020/04/08 14:08:21 martin Exp $ */ 2 1.1.6.2 martin 3 1.1.6.2 martin /*- 4 1.1.6.2 martin * Copyright (c) 2013 The NetBSD Foundation, Inc. 5 1.1.6.2 martin * All rights reserved. 6 1.1.6.2 martin * 7 1.1.6.2 martin * This code is derived from software contributed to The NetBSD Foundation 8 1.1.6.2 martin * by Taylor R. Campbell. 9 1.1.6.2 martin * 10 1.1.6.2 martin * Redistribution and use in source and binary forms, with or without 11 1.1.6.2 martin * modification, are permitted provided that the following conditions 12 1.1.6.2 martin * are met: 13 1.1.6.2 martin * 1. Redistributions of source code must retain the above copyright 14 1.1.6.2 martin * notice, this list of conditions and the following disclaimer. 15 1.1.6.2 martin * 2. Redistributions in binary form must reproduce the above copyright 16 1.1.6.2 martin * notice, this list of conditions and the following disclaimer in the 17 1.1.6.2 martin * documentation and/or other materials provided with the distribution. 18 1.1.6.2 martin * 19 1.1.6.2 martin * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 1.1.6.2 martin * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 1.1.6.2 martin * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 1.1.6.2 martin * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 1.1.6.2 martin * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 1.1.6.2 martin * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 1.1.6.2 martin * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 1.1.6.2 martin * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 1.1.6.2 martin * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 1.1.6.2 martin * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 1.1.6.2 martin * POSSIBILITY OF SUCH DAMAGE. 30 1.1.6.2 martin */ 31 1.1.6.2 martin 32 1.1.6.2 martin #ifndef _LINUX_LOG2_H_ 33 1.1.6.2 martin #define _LINUX_LOG2_H_ 34 1.1.6.2 martin 35 1.1.6.2 martin #include <sys/types.h> 36 1.1.6.2 martin #include <sys/bitops.h> 37 1.1.6.2 martin 38 1.1.6.2 martin #include <machine/limits.h> 39 1.1.6.2 martin 40 1.1.6.2 martin static inline bool 41 1.1.6.2 martin is_power_of_2(unsigned long x) 42 1.1.6.2 martin { 43 1.1.6.2 martin return ((x != 0) && (((x - 1) & x) == 0)); 44 1.1.6.2 martin } 45 1.1.6.2 martin 46 1.1.6.2 martin static inline unsigned long 47 1.1.6.2 martin roundup_pow_of_two(unsigned long n) 48 1.1.6.2 martin { 49 1.1.6.2 martin unsigned i; 50 1.1.6.2 martin 51 1.1.6.2 martin if (n == 0) 52 1.1.6.2 martin return 1; 53 1.1.6.2 martin 54 1.1.6.2 martin n -= 1; 55 1.1.6.2 martin for (i = 1; i < CHAR_BIT * sizeof n; i <<= 1) 56 1.1.6.2 martin n |= (n >> i); 57 1.1.6.2 martin 58 1.1.6.2 martin return (n + 1); 59 1.1.6.2 martin } 60 1.1.6.2 martin 61 1.1.6.2 martin static inline unsigned long 62 1.1.6.2 martin rounddown_pow_of_two(unsigned long n) 63 1.1.6.2 martin { 64 1.1.6.2 martin 65 1.1.6.2 martin /* XXX fls64 is not fls_ulong, but it'll do for now. */ 66 1.1.6.2 martin return (1UL << (fls64(n) - 1)); 67 1.1.6.2 martin } 68 1.1.6.2 martin 69 1.1.6.2 martin static inline unsigned 70 1.1.6.2 martin order_base_2(unsigned long n) 71 1.1.6.2 martin { 72 1.1.6.2 martin 73 1.1.6.2 martin return ilog2(roundup_pow_of_two(n)); 74 1.1.6.2 martin } 75 1.1.6.2 martin 76 1.1.6.2 martin #endif /* _LINUX_LOG2_H_ */ 77
Indexes created Fri Oct 03 02:09:57 GMT 2025