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
atomicBitsetInit(struct AtomicBitset * set,uint32_t numBits)24 void 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
atomicBitsetGetNumBits(const struct AtomicBitset * set)32 uint32_t atomicBitsetGetNumBits(const struct AtomicBitset *set)
33 {
34 return set->numBits;
35 }
36
atomicBitsetGetBit(const struct AtomicBitset * set,uint32_t num)37 bool 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
atomicBitsetClearBit(struct AtomicBitset * set,uint32_t num)45 void 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
atomicBitsetFindClearAndSet(struct AtomicBitset * set)61 int32_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