1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <stdint.h>
18#include <string.h>
19#include <atomicBitset.h>
20#include <atomic.h>
21
22
23
24void atomicBitsetInit(struct AtomicBitset *set, uint32_t numBits)
25{
26    set->numBits = numBits;
27    memset(set->words, 0, (numBits + 31) / 8);
28    if (numBits & 31) //mark all high bits so that atomicBitsetFindClearAndSet() is simpler
29        set->words[numBits / 32] = ((uint32_t)((int32_t)-1LL)) << (numBits & 31);
30}
31
32uint32_t atomicBitsetGetNumBits(const struct AtomicBitset *set)
33{
34    return set->numBits;
35}
36
37bool atomicBitsetGetBit(const struct AtomicBitset *set, uint32_t num)
38{
39    if (num >= set->numBits) /* any value is as good as the next */
40        return false;
41
42    return !!((set->words[num / 32]) & (1UL << (num & 31)));
43}
44
45void atomicBitsetClearBit(struct AtomicBitset *set, uint32_t num)
46{
47    uint32_t idx = num / 32, mask = 1UL << (num & 31);
48    uint32_t *wordPtr = set->words + idx;
49    uint32_t old, new;
50
51    if (num >= set->numBits)
52        return;
53
54
55    do {
56        old = *wordPtr;
57        new = old &~ mask;
58    } while (!atomicCmpXchg32bits(wordPtr, old, new));
59}
60
61int32_t atomicBitsetFindClearAndSet(struct AtomicBitset *set)
62{
63    uint32_t pos, i, numWords = (set->numBits + 31) / 32;
64    uint32_t *wordPtr = set->words;
65
66    for (i = 0; i < numWords; i++, wordPtr++) {
67        uint32_t old, new;
68
69        while (1) {
70            old = *wordPtr;
71            if (!(old + 1)) /* no work for words with no clear bits */
72                break;
73
74            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 */
75            new = old | (1 << pos);
76
77            if (atomicCmpXchg32bits(wordPtr, old, new))
78                return 32 * i + pos;
79        }
80    }
81
82    return false;
83}
84
85
86
87
88
89
90
91
92
93
94