BitSet.h revision 247da72a5bb1e762c73723fd2d495c9a6c4f1c68 
1/*
2 * Copyright (C) 2010 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#ifndef UTILS_BITSET_H
18#define UTILS_BITSET_H
19
20#include <stdint.h>
21
22/*
23 * Contains some bit manipulation helpers.
24 */
25
26namespace android {
27
28// A simple set of 32 bits that can be individually marked or cleared.
29struct BitSet32 {
30    uint32_t value;
31
32    inline BitSet32() : value(0) { }
33    explicit inline BitSet32(uint32_t value) : value(value) { }
34
35    // Gets the value associated with a particular bit index.
36    static inline uint32_t valueForBit(uint32_t n) { return 0x80000000 >> n; }
37
38    // Clears the bit set.
39    inline void clear() { value = 0; }
40
41    // Returns the number of marked bits in the set.
42    inline uint32_t count() const { return __builtin_popcount(value); }
43
44    // Returns true if the bit set does not contain any marked bits.
45    inline bool isEmpty() const { return ! value; }
46
47    // Returns true if the specified bit is marked.
48    inline bool hasBit(uint32_t n) const { return value & valueForBit(n); }
49
50    // Marks the specified bit.
51    inline void markBit(uint32_t n) { value |= valueForBit(n); }
52
53    // Clears the specified bit.
54    inline void clearBit(uint32_t n) { value &= ~ valueForBit(n); }
55
56    // Finds the first marked bit in the set.
57    // Result is undefined if all bits are unmarked.
58    inline uint32_t firstMarkedBit() const { return __builtin_clz(value); }
59
60    // Finds the first unmarked bit in the set.
61    // Result is undefined if all bits are marked.
62    inline uint32_t firstUnmarkedBit() const { return __builtin_clz(~ value); }
63
64    // Gets the index of the specified bit in the set, which is the number of
65    // marked bits that appear before the specified bit.
66    inline uint32_t getIndexOfBit(uint32_t n) const {
67        return __builtin_popcount(value & ~(0xffffffffUL >> n));
68    }
69
70    inline bool operator== (const BitSet32& other) const { return value == other.value; }
71    inline bool operator!= (const BitSet32& other) const { return value != other.value; }
72};
73
74} // namespace android
75
76#endif // UTILS_BITSET_H
77