bit_vector.h revision e77493c7217efdd1a0ecef521a6845a13da0305b
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 <iterator> 22 23namespace art { 24 25class Allocator; 26 27/* 28 * Expanding bitmap, used for tracking resources. Bits are numbered starting 29 * from zero. All operations on a BitVector are unsynchronized. 30 */ 31class BitVector { 32 public: 33 class IndexContainer; 34 35 /** 36 * @brief Convenient iterator across the indexes of the BitVector's set bits. 37 * 38 * @details IndexIterator is a Forward iterator (C++11: 24.2.5) from the lowest 39 * to the highest index of the BitVector's set bits. Instances can be retrieved 40 * only through BitVector::Indexes() which returns an IndexContainer wrapper 41 * object with begin() and end() suitable for range-based loops: 42 * for (uint32_t idx : bit_vector.Indexes()) { 43 * // Use idx. 44 * } 45 */ 46 class IndexIterator : 47 std::iterator<std::forward_iterator_tag, uint32_t, ptrdiff_t, void, uint32_t> { 48 public: 49 bool operator==(const IndexIterator& other) const; 50 51 bool operator!=(const IndexIterator& other) const { 52 return !(*this == other); 53 } 54 55 int operator*() const; 56 57 IndexIterator& operator++(); 58 59 IndexIterator operator++(int); 60 61 // Helper function to check for end without comparing with bit_vector.Indexes().end(). 62 bool Done() const { 63 return bit_index_ == BitSize(); 64 } 65 66 private: 67 struct begin_tag { }; 68 struct end_tag { }; 69 70 IndexIterator(const BitVector* bit_vector, begin_tag) 71 : bit_storage_(bit_vector->GetRawStorage()), 72 storage_size_(bit_vector->storage_size_), 73 bit_index_(FindIndex(0u)) { } 74 75 IndexIterator(const BitVector* bit_vector, end_tag) 76 : bit_storage_(bit_vector->GetRawStorage()), 77 storage_size_(bit_vector->storage_size_), 78 bit_index_(BitSize()) { } 79 80 uint32_t BitSize() const { 81 return storage_size_ * kWordBits; 82 } 83 84 uint32_t FindIndex(uint32_t start_index) const; 85 const uint32_t* const bit_storage_; 86 const uint32_t storage_size_; // Size of vector in words. 87 uint32_t bit_index_; // Current index (size in bits). 88 89 friend class BitVector::IndexContainer; 90 }; 91 92 /** 93 * @brief BitVector wrapper class for iteration across indexes of set bits. 94 */ 95 class IndexContainer { 96 public: 97 explicit IndexContainer(const BitVector* bit_vector) : bit_vector_(bit_vector) { } 98 99 IndexIterator begin() const { 100 return IndexIterator(bit_vector_, IndexIterator::begin_tag()); 101 } 102 103 IndexIterator end() const { 104 return IndexIterator(bit_vector_, IndexIterator::end_tag()); 105 } 106 107 private: 108 const BitVector* const bit_vector_; 109 }; 110 111 BitVector(uint32_t start_bits, 112 bool expandable, 113 Allocator* allocator, 114 uint32_t storage_size = 0, 115 uint32_t* storage = nullptr); 116 117 virtual ~BitVector(); 118 119 // Mark the specified bit as "set". 120 void SetBit(uint32_t idx) { 121 /* 122 * TUNING: this could have pathologically bad growth/expand behavior. Make sure we're 123 * not using it badly or change resize mechanism. 124 */ 125 if (idx >= storage_size_ * kWordBits) { 126 EnsureSize(idx); 127 } 128 storage_[WordIndex(idx)] |= BitMask(idx); 129 } 130 131 // Mark the specified bit as "unset". 132 void ClearBit(uint32_t idx) { 133 // If the index is over the size, we don't have to do anything, it is cleared. 134 if (idx < storage_size_ * kWordBits) { 135 // Otherwise, go ahead and clear it. 136 storage_[WordIndex(idx)] &= ~BitMask(idx); 137 } 138 } 139 140 // Determine whether or not the specified bit is set. 141 bool IsBitSet(uint32_t idx) const { 142 // If the index is over the size, whether it is expandable or not, this bit does not exist: 143 // thus it is not set. 144 return (idx < (storage_size_ * kWordBits)) && IsBitSet(storage_, idx); 145 } 146 147 // Mark all bits bit as "clear". 148 void ClearAllBits(); 149 150 // Mark specified number of bits as "set". Cannot set all bits like ClearAll since there might 151 // be unused bits - setting those to one will confuse the iterator. 152 void SetInitialBits(uint32_t num_bits); 153 154 void Copy(const BitVector* src); 155 156 // Intersect with another bit vector. 157 void Intersect(const BitVector* src2); 158 159 // Union with another bit vector. 160 bool Union(const BitVector* src); 161 162 // Set bits of union_with that are not in not_in. 163 bool UnionIfNotIn(const BitVector* union_with, const BitVector* not_in); 164 165 void Subtract(const BitVector* src); 166 167 // Are we equal to another bit vector? Note: expandability attributes must also match. 168 bool Equal(const BitVector* src) const; 169 170 /** 171 * @brief Are all the bits set the same? 172 * @details expandability and size can differ as long as the same bits are set. 173 */ 174 bool SameBitsSet(const BitVector *src) const; 175 176 // Count the number of bits that are set. 177 uint32_t NumSetBits() const; 178 179 // Count the number of bits that are set in range [0, end). 180 uint32_t NumSetBits(uint32_t end) const; 181 182 IndexContainer Indexes() const { 183 return IndexContainer(this); 184 } 185 186 uint32_t GetStorageSize() const { 187 return storage_size_; 188 } 189 190 bool IsExpandable() const { 191 return expandable_; 192 } 193 194 uint32_t GetRawStorageWord(size_t idx) const { 195 return storage_[idx]; 196 } 197 198 uint32_t* GetRawStorage() { 199 return storage_; 200 } 201 202 const uint32_t* GetRawStorage() const { 203 return storage_; 204 } 205 206 size_t GetSizeOf() const { 207 return storage_size_ * kWordBytes; 208 } 209 210 /** 211 * @return the highest bit set, -1 if none are set 212 */ 213 int GetHighestBitSet() const; 214 215 // Is bit set in storage. (No range check.) 216 static bool IsBitSet(const uint32_t* storage, uint32_t idx) { 217 return (storage[WordIndex(idx)] & BitMask(idx)) != 0; 218 } 219 220 // Number of bits set in range [0, end) in storage. (No range check.) 221 static uint32_t NumSetBits(const uint32_t* storage, uint32_t end); 222 223 void Dump(std::ostream& os, const char* prefix) const; 224 225 private: 226 /** 227 * @brief Dump the bitvector into buffer in a 00101..01 format. 228 * @param buffer the ostringstream used to dump the bitvector into. 229 */ 230 void DumpHelper(const char* prefix, std::ostringstream& buffer) const; 231 232 // Ensure there is space for a bit at idx. 233 void EnsureSize(uint32_t idx); 234 235 // The index of the word within storage. 236 static constexpr uint32_t WordIndex(uint32_t idx) { 237 return idx >> 5; 238 } 239 240 // A bit mask to extract the bit for the given index. 241 static constexpr uint32_t BitMask(uint32_t idx) { 242 return 1 << (idx & 0x1f); 243 } 244 245 static constexpr uint32_t kWordBytes = sizeof(uint32_t); 246 static constexpr uint32_t kWordBits = kWordBytes * 8; 247 248 uint32_t* storage_; // The storage for the bit vector. 249 uint32_t storage_size_; // Current size, in 32-bit words. 250 Allocator* const allocator_; // Allocator if expandable. 251 const bool expandable_; // Should the bitmap expand if too small? 252}; 253 254 255} // namespace art 256 257#endif // ART_RUNTIME_BASE_BIT_VECTOR_H_ 258