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