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77 lines
2.2 KiB
C
77 lines
2.2 KiB
C
/* $NetBSD: log2.h,v 1.5 2014/08/06 14:05:08 riastradh Exp $ */
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/*-
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* Copyright (c) 2013 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Taylor R. Campbell.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef _LINUX_LOG2_H_
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#define _LINUX_LOG2_H_
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#include <sys/types.h>
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#include <sys/bitops.h>
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#include <machine/limits.h>
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static inline bool
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is_power_of_2(unsigned long x)
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{
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return ((x != 0) && (((x - 1) & x) == 0));
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}
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static inline unsigned long
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roundup_pow_of_two(unsigned long n)
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{
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unsigned i;
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if (n == 0)
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return 1;
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n -= 1;
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for (i = 1; i < CHAR_BIT * sizeof n; i <<= 1)
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n |= (n >> i);
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return (n + 1);
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}
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static inline unsigned long
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rounddown_pow_of_two(unsigned long n)
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{
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/* XXX fls64 is not fls_ulong, but it'll do for now. */
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return (1UL << (fls64(n) - 1));
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}
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static inline unsigned
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order_base_2(unsigned long n)
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{
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return ilog2(roundup_pow_of_two(n));
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}
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#endif /* _LINUX_LOG2_H_ */
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