1 /* $NetBSD: log2.h,v 1.1 2020/02/16 07:29:48 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