bit_vector.h revision 067f1ed7816cf4eb5d6258ca31b387ddb2073ab7
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 26namespace art { 27 28class 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 */ 34class 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 BitVector(uint32_t start_bits, 115 bool expandable, 116 Allocator* allocator); 117 118 BitVector(bool expandable, 119 Allocator* allocator, 120 uint32_t storage_size, 121 uint32_t* storage); 122 123 BitVector(const BitVector& src, 124 bool expandable, 125 Allocator* allocator); 126 127 virtual ~BitVector(); 128 129 // The number of words necessary to encode bits. 130 static constexpr uint32_t BitsToWords(uint32_t bits) { 131 return RoundUp(bits, kWordBits) / kWordBits; 132 } 133 134 // Mark the specified bit as "set". 135 void SetBit(uint32_t idx) { 136 /* 137 * TUNING: this could have pathologically bad growth/expand behavior. Make sure we're 138 * not using it badly or change resize mechanism. 139 */ 140 if (idx >= storage_size_ * kWordBits) { 141 EnsureSize(idx); 142 } 143 storage_[WordIndex(idx)] |= BitMask(idx); 144 } 145 146 // Mark the specified bit as "unset". 147 void ClearBit(uint32_t idx) { 148 // If the index is over the size, we don't have to do anything, it is cleared. 149 if (idx < storage_size_ * kWordBits) { 150 // Otherwise, go ahead and clear it. 151 storage_[WordIndex(idx)] &= ~BitMask(idx); 152 } 153 } 154 155 // Determine whether or not the specified bit is set. 156 bool IsBitSet(uint32_t idx) const { 157 // If the index is over the size, whether it is expandable or not, this bit does not exist: 158 // thus it is not set. 159 return (idx < (storage_size_ * kWordBits)) && IsBitSet(storage_, idx); 160 } 161 162 // Mark all bits bit as "clear". 163 void ClearAllBits(); 164 165 // Mark specified number of bits as "set". Cannot set all bits like ClearAll since there might 166 // be unused bits - setting those to one will confuse the iterator. 167 void SetInitialBits(uint32_t num_bits); 168 169 void Copy(const BitVector* src); 170 171 // Intersect with another bit vector. 172 void Intersect(const BitVector* src2); 173 174 // Union with another bit vector. 175 bool Union(const BitVector* src); 176 177 // Set bits of union_with that are not in not_in. 178 bool UnionIfNotIn(const BitVector* union_with, const BitVector* not_in); 179 180 void Subtract(const BitVector* src); 181 182 // Are we equal to another bit vector? Note: expandability attributes must also match. 183 bool Equal(const BitVector* src) const; 184 185 /** 186 * @brief Are all the bits set the same? 187 * @details expandability and size can differ as long as the same bits are set. 188 */ 189 bool SameBitsSet(const BitVector *src) const; 190 191 bool IsSubsetOf(const BitVector *other) const; 192 193 // Count the number of bits that are set. 194 uint32_t NumSetBits() const; 195 196 // Count the number of bits that are set in range [0, end). 197 uint32_t NumSetBits(uint32_t end) const; 198 199 IndexContainer Indexes() const { 200 return IndexContainer(this); 201 } 202 203 uint32_t GetStorageSize() const { 204 return storage_size_; 205 } 206 207 bool IsExpandable() const { 208 return expandable_; 209 } 210 211 uint32_t GetRawStorageWord(size_t idx) const { 212 return storage_[idx]; 213 } 214 215 uint32_t* GetRawStorage() { 216 return storage_; 217 } 218 219 const uint32_t* GetRawStorage() const { 220 return storage_; 221 } 222 223 size_t GetSizeOf() const { 224 return storage_size_ * kWordBytes; 225 } 226 227 /** 228 * @return the highest bit set, -1 if none are set 229 */ 230 int GetHighestBitSet() const; 231 232 // Is bit set in storage. (No range check.) 233 static bool IsBitSet(const uint32_t* storage, uint32_t idx) { 234 return (storage[WordIndex(idx)] & BitMask(idx)) != 0; 235 } 236 237 // Number of bits set in range [0, end) in storage. (No range check.) 238 static uint32_t NumSetBits(const uint32_t* storage, uint32_t end); 239 240 // Fill given memory region with the contents of the vector and zero padding. 241 void CopyTo(void* dst, size_t len) const { 242 DCHECK_LE(static_cast<size_t>(GetHighestBitSet() + 1), len * kBitsPerByte); 243 size_t vec_len = GetSizeOf(); 244 if (vec_len < len) { 245 void* dst_padding = reinterpret_cast<uint8_t*>(dst) + vec_len; 246 memcpy(dst, storage_, vec_len); 247 memset(dst_padding, 0, len - vec_len); 248 } else { 249 memcpy(dst, storage_, len); 250 } 251 } 252 253 void Dump(std::ostream& os, const char* prefix) const; 254 255 Allocator* GetAllocator() const; 256 257 private: 258 /** 259 * @brief Dump the bitvector into buffer in a 00101..01 format. 260 * @param buffer the ostringstream used to dump the bitvector into. 261 */ 262 void DumpHelper(const char* prefix, std::ostringstream& buffer) const; 263 264 // Ensure there is space for a bit at idx. 265 void EnsureSize(uint32_t idx); 266 267 // The index of the word within storage. 268 static constexpr uint32_t WordIndex(uint32_t idx) { 269 return idx >> 5; 270 } 271 272 // A bit mask to extract the bit for the given index. 273 static constexpr uint32_t BitMask(uint32_t idx) { 274 return 1 << (idx & 0x1f); 275 } 276 277 static constexpr uint32_t kWordBytes = sizeof(uint32_t); 278 static constexpr uint32_t kWordBits = kWordBytes * 8; 279 280 uint32_t* storage_; // The storage for the bit vector. 281 uint32_t storage_size_; // Current size, in 32-bit words. 282 Allocator* const allocator_; // Allocator if expandable. 283 const bool expandable_; // Should the bitmap expand if too small? 284}; 285 286 287} // namespace art 288 289#endif // ART_RUNTIME_BASE_BIT_VECTOR_H_ 290