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/*
* Copyright (c) 2014 Richard Braun.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*
* Integer base 2 logarithm operations.
*/
#ifndef KERN_LOG2_H
#define KERN_LOG2_H
#include <assert.h>
#include <limits.h>
/*
* Return the base-2 logarithm of the given value, or of the first
* power-of-two below the given value if it's not a power-of-two.
*/
static inline unsigned int
log2(unsigned long x)
{
assert(x != 0);
return LONG_BIT - __builtin_clzl(x) - 1;
}
/*
* Return the base-2 logarithm of the given value, or of the first
* power-of-two above the given value if it's not a power-of-two.
*/
static inline unsigned int
log2_order(unsigned long size)
{
assert(size != 0);
if (size == 1) {
return 0;
}
return log2(size - 1) + 1;
}
#endif /* KERN_LOG2_H */
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