94 lines
2.4 KiB
C
94 lines
2.4 KiB
C
/*
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* Copyright (C) 2016 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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#include <stdint.h>
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#include <string.h>
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#include <atomicBitset.h>
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#include <atomic.h>
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void atomicBitsetInit(struct AtomicBitset *set, uint32_t numBits)
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{
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set->numBits = numBits;
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memset(set->words, 0, (numBits + 31) / 8);
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if (numBits & 31) //mark all high bits so that atomicBitsetFindClearAndSet() is simpler
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set->words[numBits / 32] = ((uint32_t)((int32_t)-1LL)) << (numBits & 31);
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}
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uint32_t atomicBitsetGetNumBits(const struct AtomicBitset *set)
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{
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return set->numBits;
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}
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bool atomicBitsetGetBit(const struct AtomicBitset *set, uint32_t num)
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{
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if (num >= set->numBits) /* any value is as good as the next */
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return false;
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return !!((set->words[num / 32]) & (1UL << (num & 31)));
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}
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void atomicBitsetClearBit(struct AtomicBitset *set, uint32_t num)
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{
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uint32_t idx = num / 32, mask = 1UL << (num & 31);
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uint32_t *wordPtr = set->words + idx;
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uint32_t old, new;
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if (num >= set->numBits)
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return;
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do {
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old = *wordPtr;
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new = old &~ mask;
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} while (!atomicCmpXchg32bits(wordPtr, old, new));
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}
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int32_t atomicBitsetFindClearAndSet(struct AtomicBitset *set)
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{
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uint32_t pos, i, numWords = (set->numBits + 31) / 32;
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uint32_t *wordPtr = set->words;
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for (i = 0; i < numWords; i++, wordPtr++) {
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uint32_t old, new;
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while (1) {
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old = *wordPtr;
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if (!(old + 1)) /* no work for words with no clear bits */
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break;
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pos = __builtin_ctz(~old); /* This will allocate in diff order than ARM. Since we never made any promises on order of bits returned, this is ok */
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new = old | (1 << pos);
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if (atomicCmpXchg32bits(wordPtr, old, new))
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return 32 * i + pos;
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}
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}
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return false;
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}
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