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      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