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_LIBARTBASE_BASE_BIT_VECTOR_H_ 18 #define ART_LIBARTBASE_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 IndexIterator(const BitVector* bit_vector, end_tag); 75 76 uint32_t BitSize() const { 77 return storage_size_ * kWordBits; 78 } 79 80 uint32_t FindIndex(uint32_t start_index) const; 81 const uint32_t* const bit_storage_; 82 const uint32_t storage_size_; // Size of vector in words. 83 uint32_t bit_index_; // Current index (size in bits). 84 85 friend class BitVector::IndexContainer; 86 }; 87 88 /** 89 * @brief BitVector wrapper class for iteration across indexes of set bits. 90 */ 91 class IndexContainer { 92 public: 93 explicit IndexContainer(const BitVector* bit_vector) : bit_vector_(bit_vector) { } 94 95 IndexIterator begin() const; 96 IndexIterator end() const; 97 98 private: 99 const BitVector* const bit_vector_; 100 }; 101 102 // MoveConstructible but not MoveAssignable, CopyConstructible or CopyAssignable. 103 104 BitVector(const BitVector& other) = delete; 105 BitVector& operator=(const BitVector& other) = delete; 106 107 BitVector(BitVector&& other) 108 : storage_(other.storage_), 109 storage_size_(other.storage_size_), 110 allocator_(other.allocator_), 111 expandable_(other.expandable_) { 112 other.storage_ = nullptr; 113 other.storage_size_ = 0u; 114 } 115 116 BitVector(uint32_t start_bits, 117 bool expandable, 118 Allocator* allocator); 119 120 BitVector(bool expandable, 121 Allocator* allocator, 122 uint32_t storage_size, 123 uint32_t* storage); 124 125 BitVector(const BitVector& src, 126 bool expandable, 127 Allocator* allocator); 128 129 virtual ~BitVector(); 130 131 // The number of words necessary to encode bits. 132 static constexpr uint32_t BitsToWords(uint32_t bits) { 133 return RoundUp(bits, kWordBits) / kWordBits; 134 } 135 136 // Mark the specified bit as "set". 137 void SetBit(uint32_t idx) { 138 /* 139 * TUNING: this could have pathologically bad growth/expand behavior. Make sure we're 140 * not using it badly or change resize mechanism. 141 */ 142 if (idx >= storage_size_ * kWordBits) { 143 EnsureSize(idx); 144 } 145 storage_[WordIndex(idx)] |= BitMask(idx); 146 } 147 148 // Mark the specified bit as "unset". 149 void ClearBit(uint32_t idx) { 150 // If the index is over the size, we don't have to do anything, it is cleared. 151 if (idx < storage_size_ * kWordBits) { 152 // Otherwise, go ahead and clear it. 153 storage_[WordIndex(idx)] &= ~BitMask(idx); 154 } 155 } 156 157 // Determine whether or not the specified bit is set. 158 bool IsBitSet(uint32_t idx) const { 159 // If the index is over the size, whether it is expandable or not, this bit does not exist: 160 // thus it is not set. 161 return (idx < (storage_size_ * kWordBits)) && IsBitSet(storage_, idx); 162 } 163 164 // Mark all bits bit as "clear". 165 void ClearAllBits(); 166 167 // Mark specified number of bits as "set". Cannot set all bits like ClearAll since there might 168 // be unused bits - setting those to one will confuse the iterator. 169 void SetInitialBits(uint32_t num_bits); 170 171 void Copy(const BitVector* src); 172 173 // Intersect with another bit vector. 174 void Intersect(const BitVector* src2); 175 176 // Union with another bit vector. 177 bool Union(const BitVector* src); 178 179 // Set bits of union_with that are not in not_in. 180 bool UnionIfNotIn(const BitVector* union_with, const BitVector* not_in); 181 182 void Subtract(const BitVector* src); 183 184 // Are we equal to another bit vector? Note: expandability attributes must also match. 185 bool Equal(const BitVector* src) const; 186 187 /** 188 * @brief Are all the bits set the same? 189 * @details expandability and size can differ as long as the same bits are set. 190 */ 191 bool SameBitsSet(const BitVector *src) const; 192 193 bool IsSubsetOf(const BitVector *other) const; 194 195 // Count the number of bits that are set. 196 uint32_t NumSetBits() const; 197 198 // Count the number of bits that are set in range [0, end). 199 uint32_t NumSetBits(uint32_t end) const; 200 201 IndexContainer Indexes() const { 202 return IndexContainer(this); 203 } 204 205 uint32_t GetStorageSize() const { 206 return storage_size_; 207 } 208 209 bool IsExpandable() const { 210 return expandable_; 211 } 212 213 uint32_t GetRawStorageWord(size_t idx) const { 214 return storage_[idx]; 215 } 216 217 uint32_t* GetRawStorage() { 218 return storage_; 219 } 220 221 const uint32_t* GetRawStorage() const { 222 return storage_; 223 } 224 225 size_t GetSizeOf() const { 226 return storage_size_ * kWordBytes; 227 } 228 229 /** 230 * @return the highest bit set, -1 if none are set 231 */ 232 int GetHighestBitSet() const; 233 234 // Minimum number of bits required to store this vector, 0 if none are set. 235 size_t GetNumberOfBits() const { 236 return GetHighestBitSet() + 1; 237 } 238 239 // Is bit set in storage. (No range check.) 240 static bool IsBitSet(const uint32_t* storage, uint32_t idx) { 241 return (storage[WordIndex(idx)] & BitMask(idx)) != 0; 242 } 243 244 // Number of bits set in range [0, end) in storage. (No range check.) 245 static uint32_t NumSetBits(const uint32_t* storage, uint32_t end); 246 247 // Fill given memory region with the contents of the vector and zero padding. 248 void CopyTo(void* dst, size_t len) const { 249 DCHECK_LE(static_cast<size_t>(GetHighestBitSet() + 1), len * kBitsPerByte); 250 size_t vec_len = GetSizeOf(); 251 if (vec_len < len) { 252 void* dst_padding = reinterpret_cast<uint8_t*>(dst) + vec_len; 253 memcpy(dst, storage_, vec_len); 254 memset(dst_padding, 0, len - vec_len); 255 } else { 256 memcpy(dst, storage_, len); 257 } 258 } 259 260 void Dump(std::ostream& os, const char* prefix) const; 261 262 Allocator* GetAllocator() const; 263 264 private: 265 /** 266 * @brief Dump the bitvector into buffer in a 00101..01 format. 267 * @param buffer the ostringstream used to dump the bitvector into. 268 */ 269 void DumpHelper(const char* prefix, std::ostringstream& buffer) const; 270 271 // Ensure there is space for a bit at idx. 272 void EnsureSize(uint32_t idx); 273 274 // The index of the word within storage. 275 static constexpr uint32_t WordIndex(uint32_t idx) { 276 return idx >> 5; 277 } 278 279 // A bit mask to extract the bit for the given index. 280 static constexpr uint32_t BitMask(uint32_t idx) { 281 return 1 << (idx & 0x1f); 282 } 283 284 static constexpr uint32_t kWordBytes = sizeof(uint32_t); 285 static constexpr uint32_t kWordBits = kWordBytes * 8; 286 287 uint32_t* storage_; // The storage for the bit vector. 288 uint32_t storage_size_; // Current size, in 32-bit words. 289 Allocator* const allocator_; // Allocator if expandable. 290 const bool expandable_; // Should the bitmap expand if too small? 291 }; 292 293 294 } // namespace art 295 296 #endif // ART_LIBARTBASE_BASE_BIT_VECTOR_H_ 297
