bit_vector.h revision 520f37bb5c34c5d86ad0091cb84a84c163a2fa9c 
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    bool Union(const BitVector* src);
107
108    // Set bits of union_with that are not in not_in.
109    bool UnionIfNotIn(const BitVector* union_with, const BitVector* not_in);
110
111    void Subtract(const BitVector* src);
112    // Are we equal to another bit vector?  Note: expandability attributes must also match.
113    bool Equal(const BitVector* src) {
114      return (storage_size_ == src->GetStorageSize()) &&
115        (expandable_ == src->IsExpandable()) &&
116        (memcmp(storage_, src->GetRawStorage(), storage_size_ * sizeof(uint32_t)) == 0);
117    }
118
119    /**
120     * @brief Are all the bits set the same?
121     * @details expandability and size can differ as long as the same bits are set.
122     */
123    bool SameBitsSet(const BitVector *src);
124
125    uint32_t NumSetBits() const;
126
127    // Number of bits set in range [0, end).
128    uint32_t NumSetBits(uint32_t end) const;
129
130    Iterator* GetIterator() const;
131
132    uint32_t GetStorageSize() const { return storage_size_; }
133    bool IsExpandable() const { return expandable_; }
134    uint32_t GetRawStorageWord(size_t idx) const { return storage_[idx]; }
135    uint32_t* GetRawStorage() { return storage_; }
136    const uint32_t* GetRawStorage() const { return storage_; }
137    size_t GetSizeOf() const { return storage_size_ * sizeof(uint32_t); }
138
139    /**
140     * @return the highest bit set, -1 if none are set
141     */
142    int GetHighestBitSet() const;
143
144    // Is bit set in storage. (No range check.)
145    static bool IsBitSet(const uint32_t* storage, uint32_t num);
146    // Number of bits set in range [0, end) in storage. (No range check.)
147    static uint32_t NumSetBits(const uint32_t* storage, uint32_t end);
148
149    bool EnsureSizeAndClear(unsigned int num);
150
151    void Dump(std::ostream& os, const char* prefix) const;
152
153    /**
154     * @brief last_entry is this the last entry for the dot dumping
155     * @details if not, a "|" is appended to the dump.
156     */
157    void DumpDot(FILE* file, const char* prefix, bool last_entry = false) const;
158
159    /**
160     * @brief last_entry is this the last entry for the dot dumping
161     * @details if not, a "|" is appended to the dump.
162     */
163    void DumpIndicesDot(FILE* file, const char* prefix, bool last_entry = false) const;
164
165  protected:
166    /**
167     * @brief Dump the bitvector into buffer in a 00101..01 format.
168     * @param buffer the ostringstream used to dump the bitvector into.
169     */
170    void DumpHelper(const char* prefix, std::ostringstream& buffer) const;
171
172    /**
173     * @brief Dump the bitvector in a 1 2 5 8 format, where the numbers are the bit set.
174     * @param buffer the ostringstream used to dump the bitvector into.
175     */
176    void DumpIndicesHelper(const char* prefix, std::ostringstream& buffer) const;
177
178    /**
179     * @brief Wrapper to perform the bitvector dumping with the .dot format.
180     * @param buffer the ostringstream used to dump the bitvector into.
181     */
182    void DumpDotHelper(bool last_entry, FILE* file, std::ostringstream& buffer) const;
183
184  private:
185    Allocator* const allocator_;
186    const bool expandable_;         // expand bitmap if we run out?
187    uint32_t   storage_size_;       // current size, in 32-bit words.
188    uint32_t*  storage_;
189    uint32_t number_of_bits_;
190};
191
192
193}  // namespace art
194
195#endif  // ART_RUNTIME_BASE_BIT_VECTOR_H_
196