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 23 #include "base/bit_utils.h" 24 #include "globals.h" 25 26 namespace art { 27 28 class Allocator; 29 30 /* 31 * Expanding bitmap, used for tracking resources. Bits are numbered starting 32 * from zero. All operations on a BitVector are unsynchronized. 33 */ 34 class BitVector { 35 public: 36 class IndexContainer; 37 38 /** 39 * @brief Convenient iterator across the indexes of the BitVector's set bits. 40 * 41 * @details IndexIterator is a Forward iterator (C++11: 24.2.5) from the lowest 42 * to the highest index of the BitVector's set bits. Instances can be retrieved 43 * only through BitVector::Indexes() which returns an IndexContainer wrapper 44 * object with begin() and end() suitable for range-based loops: 45 * for (uint32_t idx : bit_vector.Indexes()) { 46 * // Use idx. 47 * } 48 */ 49 class IndexIterator : 50 std::iterator<std::forward_iterator_tag, uint32_t, ptrdiff_t, void, uint32_t> { 51 public: 52 bool operator==(const IndexIterator& other) const; 53 54 bool operator!=(const IndexIterator& other) const { 55 return !(*this == other); 56 } 57 58 uint32_t operator*() const; 59 60 IndexIterator& operator++(); 61 62 IndexIterator operator++(int); 63 64 // Helper function to check for end without comparing with bit_vector.Indexes().end(). 65 bool Done() const { 66 return bit_index_ == BitSize(); 67 } 68 69 private: 70 struct begin_tag { }; 71 struct end_tag { }; 72 73 IndexIterator(const BitVector* bit_vector, begin_tag) 74 : bit_storage_(bit_vector->GetRawStorage()), 75 storage_size_(bit_vector->storage_size_), 76 bit_index_(FindIndex(0u)) { } 77 78 IndexIterator(const BitVector* bit_vector, end_tag) 79 : bit_storage_(bit_vector->GetRawStorage()), 80 storage_size_(bit_vector->storage_size_), 81 bit_index_(BitSize()) { } 82 83 uint32_t BitSize() const { 84 return storage_size_ * kWordBits; 85 } 86 87 uint32_t FindIndex(uint32_t start_index) const; 88 const uint32_t* const bit_storage_; 89 const uint32_t storage_size_; // Size of vector in words. 90 uint32_t bit_index_; // Current index (size in bits). 91 92 friend class BitVector::IndexContainer; 93 }; 94 95 /** 96 * @brief BitVector wrapper class for iteration across indexes of set bits. 97 */ 98 class IndexContainer { 99 public: 100 explicit IndexContainer(const BitVector* bit_vector) : bit_vector_(bit_vector) { } 101 102 IndexIterator begin() const { 103 return IndexIterator(bit_vector_, IndexIterator::begin_tag()); 104 } 105 106 IndexIterator end() const { 107 return IndexIterator(bit_vector_, IndexIterator::end_tag()); 108 } 109 110 private: 111 const BitVector* const bit_vector_; 112 }; 113 114 // MoveConstructible but not MoveAssignable, CopyConstructible or CopyAssignable. 115 116 BitVector(const BitVector& other) = delete; 117 BitVector& operator=(const BitVector& other) = delete; 118 119 BitVector(BitVector&& other) 120 : storage_(other.storage_), 121 storage_size_(other.storage_size_), 122 allocator_(other.allocator_), 123 expandable_(other.expandable_) { 124 other.storage_ = nullptr; 125 other.storage_size_ = 0u; 126 } 127 128 BitVector(uint32_t start_bits, 129 bool expandable, 130 Allocator* allocator); 131 132 BitVector(bool expandable, 133 Allocator* allocator, 134 uint32_t storage_size, 135 uint32_t* storage); 136 137 BitVector(const BitVector& src, 138 bool expandable, 139 Allocator* allocator); 140 141 virtual ~BitVector(); 142 143 // The number of words necessary to encode bits. 144 static constexpr uint32_t BitsToWords(uint32_t bits) { 145 return RoundUp(bits, kWordBits) / kWordBits; 146 } 147 148 // Mark the specified bit as "set". 149 void SetBit(uint32_t idx) { 150 /* 151 * TUNING: this could have pathologically bad growth/expand behavior. Make sure we're 152 * not using it badly or change resize mechanism. 153 */ 154 if (idx >= storage_size_ * kWordBits) { 155 EnsureSize(idx); 156 } 157 storage_[WordIndex(idx)] |= BitMask(idx); 158 } 159 160 // Mark the specified bit as "unset". 161 void ClearBit(uint32_t idx) { 162 // If the index is over the size, we don't have to do anything, it is cleared. 163 if (idx < storage_size_ * kWordBits) { 164 // Otherwise, go ahead and clear it. 165 storage_[WordIndex(idx)] &= ~BitMask(idx); 166 } 167 } 168 169 // Determine whether or not the specified bit is set. 170 bool IsBitSet(uint32_t idx) const { 171 // If the index is over the size, whether it is expandable or not, this bit does not exist: 172 // thus it is not set. 173 return (idx < (storage_size_ * kWordBits)) && IsBitSet(storage_, idx); 174 } 175 176 // Mark all bits bit as "clear". 177 void ClearAllBits(); 178 179 // Mark specified number of bits as "set". Cannot set all bits like ClearAll since there might 180 // be unused bits - setting those to one will confuse the iterator. 181 void SetInitialBits(uint32_t num_bits); 182 183 void Copy(const BitVector* src); 184 185 // Intersect with another bit vector. 186 void Intersect(const BitVector* src2); 187 188 // Union with another bit vector. 189 bool Union(const BitVector* src); 190 191 // Set bits of union_with that are not in not_in. 192 bool UnionIfNotIn(const BitVector* union_with, const BitVector* not_in); 193 194 void Subtract(const BitVector* src); 195 196 // Are we equal to another bit vector? Note: expandability attributes must also match. 197 bool Equal(const BitVector* src) const; 198 199 /** 200 * @brief Are all the bits set the same? 201 * @details expandability and size can differ as long as the same bits are set. 202 */ 203 bool SameBitsSet(const BitVector *src) const; 204 205 bool IsSubsetOf(const BitVector *other) const; 206 207 // Count the number of bits that are set. 208 uint32_t NumSetBits() const; 209 210 // Count the number of bits that are set in range [0, end). 211 uint32_t NumSetBits(uint32_t end) const; 212 213 IndexContainer Indexes() const { 214 return IndexContainer(this); 215 } 216 217 uint32_t GetStorageSize() const { 218 return storage_size_; 219 } 220 221 bool IsExpandable() const { 222 return expandable_; 223 } 224 225 uint32_t GetRawStorageWord(size_t idx) const { 226 return storage_[idx]; 227 } 228 229 uint32_t* GetRawStorage() { 230 return storage_; 231 } 232 233 const uint32_t* GetRawStorage() const { 234 return storage_; 235 } 236 237 size_t GetSizeOf() const { 238 return storage_size_ * kWordBytes; 239 } 240 241 /** 242 * @return the highest bit set, -1 if none are set 243 */ 244 int GetHighestBitSet() const; 245 246 // Minimum number of bits required to store this vector, 0 if none are set. 247 size_t GetNumberOfBits() const { 248 return GetHighestBitSet() + 1; 249 } 250 251 // Is bit set in storage. (No range check.) 252 static bool IsBitSet(const uint32_t* storage, uint32_t idx) { 253 return (storage[WordIndex(idx)] & BitMask(idx)) != 0; 254 } 255 256 // Number of bits set in range [0, end) in storage. (No range check.) 257 static uint32_t NumSetBits(const uint32_t* storage, uint32_t end); 258 259 // Fill given memory region with the contents of the vector and zero padding. 260 void CopyTo(void* dst, size_t len) const { 261 DCHECK_LE(static_cast<size_t>(GetHighestBitSet() + 1), len * kBitsPerByte); 262 size_t vec_len = GetSizeOf(); 263 if (vec_len < len) { 264 void* dst_padding = reinterpret_cast<uint8_t*>(dst) + vec_len; 265 memcpy(dst, storage_, vec_len); 266 memset(dst_padding, 0, len - vec_len); 267 } else { 268 memcpy(dst, storage_, len); 269 } 270 } 271 272 void Dump(std::ostream& os, const char* prefix) const; 273 274 Allocator* GetAllocator() const; 275 276 private: 277 /** 278 * @brief Dump the bitvector into buffer in a 00101..01 format. 279 * @param buffer the ostringstream used to dump the bitvector into. 280 */ 281 void DumpHelper(const char* prefix, std::ostringstream& buffer) const; 282 283 // Ensure there is space for a bit at idx. 284 void EnsureSize(uint32_t idx); 285 286 // The index of the word within storage. 287 static constexpr uint32_t WordIndex(uint32_t idx) { 288 return idx >> 5; 289 } 290 291 // A bit mask to extract the bit for the given index. 292 static constexpr uint32_t BitMask(uint32_t idx) { 293 return 1 << (idx & 0x1f); 294 } 295 296 static constexpr uint32_t kWordBytes = sizeof(uint32_t); 297 static constexpr uint32_t kWordBits = kWordBytes * 8; 298 299 uint32_t* storage_; // The storage for the bit vector. 300 uint32_t storage_size_; // Current size, in 32-bit words. 301 Allocator* const allocator_; // Allocator if expandable. 302 const bool expandable_; // Should the bitmap expand if too small? 303 }; 304 305 306 } // namespace art 307 308 #endif // ART_RUNTIME_BASE_BIT_VECTOR_H_ 309
