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/* nbdkit
* Copyright Red Hat
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of Red Hat nor the names of its contributors may be
* used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef NBDKIT_ISPOWEROF2_H
#define NBDKIT_ISPOWEROF2_H
#include <stdbool.h>
/* Returns true if v is a power of 2.
*
* Uses the algorithm described at
* http://graphics.stanford.edu/~seander/bithacks.html#DetermineIfPowerOf2
*/
static inline bool
is_power_of_2 (unsigned long v)
{
return v && ((v & (v - 1)) == 0);
}
/* Calculate log2(v) which is the size of the equivalent bit shift
* for a power of 2. For example log_2_bits (512) == 9.
*
* Note this is undefined for v == 0.
*
* __builtin_clzl is available in GCC and clang.
*/
static inline int
log_2_bits (unsigned long v)
{
return SIZEOF_LONG*8 - __builtin_clzl (v) - 1;
}
#endif /* NBDKIT_ISPOWEROF2_H */
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