bit_vector.h revision d3c5bebcb52a67cb06e7ab303eaf45f230c08b60 
1/*
2 * Copyright (C) 2013 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 ART_RUNTIME_BASE_BIT_VECTOR_H_
18#define ART_RUNTIME_BASE_BIT_VECTOR_H_
19
20#include <stdint.h>
21#include <stddef.h>
22
23#include "allocator.h"
24#include "base/logging.h"
25#include "utils.h"
26
27namespace art {
28
29/*
30 * Expanding bitmap, used for tracking resources.  Bits are numbered starting
31 * from zero.  All operations on a BitVector are unsynchronized.
32 */
33class BitVector {
34  public:
35    class Iterator {
36      public:
37        explicit Iterator(const BitVector* bit_vector)
38          : p_bits_(bit_vector),
39            bit_storage_(bit_vector->GetRawStorage()),
40            bit_index_(0),
41            bit_size_(p_bits_->storage_size_ * sizeof(uint32_t) * 8) {}
42
43        // Return the position of the next set bit.  -1 means end-of-element reached.
44        int32_t Next() {
45          // Did anything obviously change since we started?
46          DCHECK_EQ(bit_size_, p_bits_->GetStorageSize() * sizeof(uint32_t) * 8);
47          DCHECK_EQ(bit_storage_, p_bits_->GetRawStorage());
48
49          if (UNLIKELY(bit_index_ >= bit_size_)) {
50            return -1;
51          }
52
53          uint32_t word_index = bit_index_ / 32;
54          uint32_t word = bit_storage_[word_index];
55          // Mask out any bits in the first word we've already considered.
56          word >>= bit_index_ & 0x1f;
57          if (word == 0) {
58            bit_index_ &= ~0x1f;
59            do {
60              word_index++;
61              if (UNLIKELY((word_index * 32) >= bit_size_)) {
62                bit_index_ = bit_size_;
63                return -1;
64              }
65              word = bit_storage_[word_index];
66              bit_index_ += 32;
67            } while (word == 0);
68          }
69          bit_index_ += CTZ(word) + 1;
70          return bit_index_ - 1;
71        }
72
73        static void* operator new(size_t size, Allocator* allocator) {
74          return allocator->Alloc(sizeof(BitVector::Iterator));
75        };
76        static void operator delete(void* p) {
77          Iterator* it = reinterpret_cast<Iterator*>(p);
78          it->p_bits_->allocator_->Free(p);
79        }
80
81      private:
82        const BitVector* const p_bits_;
83        const uint32_t* const bit_storage_;
84        uint32_t bit_index_;           // Current index (size in bits).
85        const uint32_t bit_size_;      // Size of vector in bits.
86
87        friend class BitVector;
88    };
89
90    BitVector(uint32_t start_bits,
91              bool expandable,
92              Allocator* allocator,
93              uint32_t storage_size = 0,
94              uint32_t* storage = nullptr);
95
96    virtual ~BitVector();
97
98    void SetBit(uint32_t num);
99    void ClearBit(uint32_t num);
100    bool IsBitSet(uint32_t num) const;
101    void ClearAllBits();
102    void SetInitialBits(uint32_t num_bits);
103
104    void Copy(const BitVector* src);
105    void Intersect(const BitVector* src2);
106    void Union(const BitVector* src);
107    void Subtract(const BitVector* src);
108    // Are we equal to another bit vector?  Note: expandability attributes must also match.
109    bool Equal(const BitVector* src) {
110      return (storage_size_ == src->GetStorageSize()) &&
111        (expandable_ == src->IsExpandable()) &&
112        (memcmp(storage_, src->GetRawStorage(), storage_size_ * sizeof(uint32_t)) == 0);
113    }
114
115    /**
116     * @brief Are all the bits set the same?
117     * @details expandability and size can differ as long as the same bits are set.
118     */
119    bool SameBitsSet(const BitVector *src);
120
121    uint32_t NumSetBits() const;
122
123    // Number of bits set in range [0, end).
124    uint32_t NumSetBits(uint32_t end) const;
125
126    Iterator* GetIterator() const;
127
128    uint32_t GetStorageSize() const { return storage_size_; }
129    bool IsExpandable() const { return expandable_; }
130    uint32_t GetRawStorageWord(size_t idx) const { return storage_[idx]; }
131    uint32_t* GetRawStorage() { return storage_; }
132    const uint32_t* GetRawStorage() const { return storage_; }
133    size_t GetSizeOf() const { return storage_size_ * sizeof(uint32_t); }
134
135    /**
136     * @return the highest bit set, -1 if none are set
137     */
138    int GetHighestBitSet() const;
139
140    // Is bit set in storage. (No range check.)
141    static bool IsBitSet(const uint32_t* storage, uint32_t num);
142    // Number of bits set in range [0, end) in storage. (No range check.)
143    static uint32_t NumSetBits(const uint32_t* storage, uint32_t end);
144
145  private:
146    Allocator* const allocator_;
147    const bool expandable_;         // expand bitmap if we run out?
148    uint32_t   storage_size_;       // current size, in 32-bit words.
149    uint32_t*  storage_;
150};
151
152
153}  // namespace art
154
155#endif  // ART_RUNTIME_BASE_BIT_VECTOR_H_
156