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/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef __CUTILS_BITOPS_H
#define __CUTILS_BITOPS_H
#include <stdbool.h>
#include <string.h>
#include <strings.h>
#include <sys/cdefs.h>
__BEGIN_DECLS
/*
* Bitmask Operations
*
* Note this doesn't provide any locking/exclusion, and isn't atomic.
* Additionally no bounds checking is done on the bitmask array.
*
* Example:
*
* int num_resources;
* unsigned int resource_bits[BITS_TO_WORDS(num_resources)];
* bitmask_init(resource_bits, num_resources);
* ...
* int bit = bitmask_ffz(resource_bits, num_resources);
* bitmask_set(resource_bits, bit);
* ...
* if (bitmask_test(resource_bits, bit)) { ... }
* ...
* bitmask_clear(resource_bits, bit);
*
*/
#define BITS_PER_WORD (sizeof(unsigned int) * 8)
#define BITS_TO_WORDS(x) (((x) + BITS_PER_WORD - 1) / BITS_PER_WORD)
#define BIT_IN_WORD(x) ((x) % BITS_PER_WORD)
#define BIT_WORD(x) ((x) / BITS_PER_WORD)
#define BIT_MASK(x) (1 << BIT_IN_WORD(x))
static inline void bitmask_init(unsigned int *bitmask, int num_bits)
{
memset(bitmask, 0, BITS_TO_WORDS(num_bits)*sizeof(unsigned int));
}
static inline int bitmask_ffz(unsigned int *bitmask, int num_bits)
{
int bit, result;
size_t i;
for (i = 0; i < BITS_TO_WORDS(num_bits); i++) {
bit = ffs(~bitmask[i]);
if (bit) {
// ffs is 1-indexed, return 0-indexed result
bit--;
result = BITS_PER_WORD * i + bit;
if (result >= num_bits)
return -1;
return result;
}
}
return -1;
}
static inline int bitmask_weight(unsigned int *bitmask, int num_bits)
{
size_t i;
int weight = 0;
for (i = 0; i < BITS_TO_WORDS(num_bits); i++)
weight += __builtin_popcount(bitmask[i]);
return weight;
}
static inline void bitmask_set(unsigned int *bitmask, int bit)
{
bitmask[BIT_WORD(bit)] |= BIT_MASK(bit);
}
static inline void bitmask_clear(unsigned int *bitmask, int bit)
{
bitmask[BIT_WORD(bit)] &= ~BIT_MASK(bit);
}
static inline bool bitmask_test(unsigned int *bitmask, int bit)
{
return bitmask[BIT_WORD(bit)] & BIT_MASK(bit);
}
static inline int popcount(unsigned int x)
{
return __builtin_popcount(x);
}
static inline int popcountl(unsigned long x)
{
return __builtin_popcountl(x);
}
static inline int popcountll(unsigned long long x)
{
return __builtin_popcountll(x);
}
__END_DECLS
#endif /* __CUTILS_BITOPS_H */
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