bit_vector.h revision ba150c37d582eeeb8c11ba5245edc281cf31793c 
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_)) return -1;
50
51          uint32_t word_index = bit_index_ / 32;
52          uint32_t word = bit_storage_[word_index];
53          // Mask out any bits in the first word we've already considered.
54          word >>= bit_index_ & 0x1f;
55          if (word == 0) {
56            bit_index_ &= ~0x1f;
57            do {
58              word_index++;
59              if (UNLIKELY((word_index * 32) >= bit_size_)) {
60                bit_index_ = bit_size_;
61                return -1;
62              }
63              word = bit_storage_[word_index];
64              bit_index_ += 32;
65            } while (word == 0);
66          }
67          bit_index_ += CTZ(word) + 1;
68          return bit_index_ - 1;
69        }
70
71        static void* operator new(size_t size, Allocator* allocator) {
72          return allocator->Alloc(sizeof(BitVector::Iterator));
73        };
74        static void operator delete(void* p) {
75          Iterator* it = reinterpret_cast<Iterator*>(p);
76          it->p_bits_->allocator_->Free(p);
77        }
78
79      private:
80        const BitVector* const p_bits_;
81        const uint32_t* const bit_storage_;
82        uint32_t bit_index_;           // Current index (size in bits).
83        const uint32_t bit_size_;      // Size of vector in bits.
84
85        friend class BitVector;
86    };
87
88    BitVector(uint32_t start_bits,
89              bool expandable,
90              Allocator* allocator,
91              uint32_t storage_size = 0,
92              uint32_t* storage = NULL);
93
94    virtual ~BitVector();
95
96    void SetBit(uint32_t num);
97    void ClearBit(uint32_t num);
98    bool IsBitSet(uint32_t num) const;
99    void ClearAllBits();
100    void SetInitialBits(uint32_t num_bits);
101    void Copy(BitVector* src) {
102      memcpy(storage_, src->GetRawStorage(), sizeof(uint32_t) * storage_size_);
103    }
104    void Intersect(const BitVector* src2);
105    void Union(const BitVector* src);
106    // Are we equal to another bit vector?  Note: expandability attributes must also match.
107    bool Equal(const BitVector* src) {
108      return (storage_size_ == src->GetStorageSize()) &&
109        (expandable_ == src->IsExpandable()) &&
110        (memcmp(storage_, src->GetRawStorage(), storage_size_ * sizeof(uint32_t)) == 0);
111    }
112    uint32_t NumSetBits() const;
113    uint32_t NumSetBits(uint32_t num) const;
114
115    Iterator* GetIterator() const;
116
117    uint32_t GetStorageSize() const { return storage_size_; }
118    bool IsExpandable() const { return expandable_; }
119    uint32_t GetRawStorageWord(size_t idx) const { return storage_[idx]; }
120    uint32_t* GetRawStorage() { return storage_; }
121    const uint32_t* GetRawStorage() const { return storage_; }
122    size_t GetSizeOf() const { return storage_size_ * sizeof(uint32_t); }
123
124  private:
125    Allocator* const allocator_;
126    const bool expandable_;         // expand bitmap if we run out?
127    uint32_t   storage_size_;       // current size, in 32-bit words.
128    uint32_t*  storage_;
129};
130
131
132}  // namespace art
133
134#endif  // ART_RUNTIME_BASE_BIT_VECTOR_H_
135