1 /* 2 * Copyright (C) 2016 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 CHRE_UTIL_DYNAMIC_VECTOR_H_ 18 #define CHRE_UTIL_DYNAMIC_VECTOR_H_ 19 20 #include <cstddef> 21 22 #include "chre/util/non_copyable.h" 23 24 namespace chre { 25 26 /** 27 * A container for storing a sequential array of elements. This container 28 * resizes dynamically using heap allocations. 29 */ 30 template<typename ElementType> 31 class DynamicVector : public NonCopyable { 32 public: 33 /** 34 * Default-constructs a dynamic vector. 35 */ 36 DynamicVector(); 37 38 /** 39 * Move-constructs a dynamic vector from another. The other dynamic vector is 40 * left in an empty state. 41 * 42 * @param other The other vector to move from. 43 */ 44 DynamicVector(DynamicVector<ElementType>&& other); 45 46 /** 47 * Destructs the objects and releases the memory owned by the vector. 48 */ 49 ~DynamicVector(); 50 51 /** 52 * Removes all elements from the vector, but does not change the capacity. 53 * All iterators and references are invalidated. 54 */ 55 void clear(); 56 57 /** 58 * Returns a pointer to the underlying buffer. Note that this should not be 59 * considered to be persistent as the vector will be moved and resized 60 * automatically. 61 * 62 * @return The pointer to the underlying buffer. 63 */ 64 ElementType *data(); 65 66 /** 67 * Returns a const pointer to the underlying buffer. Note that this should not 68 * be considered to be persistent as the vector will be moved and resized 69 * automatically. 70 * 71 * @return The const pointer to the underlying buffer. 72 */ 73 const ElementType *data() const; 74 75 /** 76 * Returns the current number of elements in the vector. 77 * 78 * @return The number of elements in the vector. 79 */ 80 size_t size() const; 81 82 /** 83 * Returns the maximum number of elements that can be stored in this vector 84 * without a resize operation. 85 * 86 * @return The capacity of the vector. 87 */ 88 size_t capacity() const; 89 90 /** 91 * Determines whether the vector is empty or not. 92 * 93 * @return true if the vector is empty. 94 */ 95 bool empty() const; 96 97 /** 98 * Copy- or move-constructs an element onto the back of the vector. If the 99 * vector requires a resize and that allocation fails this function will 100 * return false. All iterators and references are invalidated if the container 101 * has been resized. Otherwise, only the past-the-end iterator is invalidated. 102 * 103 * @param The element to push onto the vector. 104 * @return true if the element was pushed successfully. 105 */ 106 bool push_back(const ElementType& element); 107 bool push_back(ElementType&& element); 108 109 /** 110 * Constructs an element onto the back of the vector. All iterators and 111 * references are invalidated if the container has been resized. Otherwise, 112 * only the past-the-end iterator is invalidated. 113 * 114 * @param The arguments to the constructor 115 * @return true is the element is constructed successfully. 116 */ 117 template<typename... Args> 118 bool emplace_back(Args&&... args); 119 120 /** 121 * Obtains an element of the vector given an index. It is illegal to index 122 * this vector out of bounds and the user of the API must check the size() 123 * function prior to indexing this vector to ensure that they will not read 124 * out of bounds. 125 * 126 * @param The index of the element. 127 * @return The element. 128 */ 129 ElementType& operator[](size_t index); 130 131 /** 132 * Obtains a const element of the vector given an index. It is illegal to 133 * index this vector out of bounds and the user of the API must check the 134 * size() function prior to indexing this vector to ensure that they will not 135 * read out of bounds. 136 * 137 * @param The index of the element. 138 * @return The element. 139 */ 140 const ElementType& operator[](size_t index) const; 141 142 /** 143 * Resizes the vector to a new capacity returning true if allocation was 144 * successful. If the new capacity is smaller than the current capacity, 145 * the operation is a no-op and true is returned. If a memory allocation 146 * fails, the contents of the vector are not modified and false is returned. 147 * This is intended to be similar to the reserve function of the std::vector. 148 * All iterators and references are invalidated unless the container did not 149 * resize. 150 * 151 * @param The new capacity of the vector. 152 * @return true if the resize operation was successful. 153 */ 154 bool reserve(size_t newCapacity); 155 156 /** 157 * Inserts an element into the vector at a given index. If a resize of the 158 * vector is required and the allocation fails, false will be returned. This 159 * will shift all vector elements after the given index one position backward 160 * in the list. The supplied index must be <= the size of the vector. It is 161 * not possible to have a sparse list of items. If the index is > the current 162 * size of the vector, false will be returned. All iterators and references 163 * to and after the indexed element are invalidated. Iterators and references 164 * to before the indexed elements are unaffected if the container did not resize. 165 * 166 * @param index The index to insert an element at. 167 * @param element The element to insert. 168 * @return Whether or not the insert operation was successful. 169 */ 170 bool insert(size_t index, const ElementType& element); 171 bool insert(size_t index, ElementType&& element); 172 173 /** 174 * Similar to wrap(), except makes a copy of the supplied C-style array, 175 * maintaining ownership of the buffer within the DynamicVector container. The 176 * vector's capacity is increased if necessary to fit the given array, though 177 * note that this function will not cause the capacity to shrink. Upon 178 * successful reservation of necessary capacity, any pre-existing items in the 179 * vector are removed (via clear()), the supplied array is copied, and the 180 * vector's size is set to elementCount. All iterators and references are 181 * invalidated unless the container did not resize. 182 * 183 * This is essentially equivalent to calling these functions from std::vector: 184 * vector.clear(); 185 * vector.insert(vector.begin(), array, &array[elementCount]); 186 * 187 * This function is not valid to call on a vector where owns_data() is false. 188 * Use unwrap() first in that case. 189 * 190 * @param array Pointer to the start of an array 191 * @param elementCount Number of elements in the supplied array to copy 192 * 193 * @return true if capacity was reserved to fit the supplied array (or the 194 * vector already had sufficient capacity), and the supplied array was 195 * copied into the vector. If false, the vector is not modified. 196 */ 197 bool copy_array(const ElementType *array, size_t elementCount); 198 199 /** 200 * Removes an element from the vector given an index. All elements after the 201 * indexed one are moved forward one position. The destructor is invoked on 202 * on the invalid item left at the end of the vector. The index passed in 203 * must be less than the size() of the vector. If the index is greater than or 204 * equal to the size no operation is performed. All iterators and references 205 * to and after the indexed element are invalidated. 206 * 207 * @param index The index to remove an element at. 208 */ 209 void erase(size_t index); 210 211 /** 212 * Searches the vector for an element. 213 * 214 * @param element The element to comare against. 215 * @return The index of the element found. If the return is equal to size() 216 * then the element was not found. 217 */ 218 size_t find(const ElementType& element) const; 219 220 /** 221 * Swaps the location of two elements stored in the vector. The indices 222 * passed in must be less than the size() of the vector. If the index is 223 * greater than or equal to the size, no operation is performed. All 224 * iterators and references to these two indexed elements are invalidated. 225 * 226 * @param index0 The index of the first element 227 * @param index1 The index of the second element 228 */ 229 void swap(size_t index0, size_t index1); 230 231 /** 232 * Wraps an existing C-style array so it can be used as a DynamicVector. A 233 * reference to the supplied array is kept, as opposed to making a copy. The 234 * caller retains ownership of the memory. Calling code must therefore ensure 235 * that the lifetime of the supplied array is at least as long as that of this 236 * vector, and that the memory is released after this vector is destructed, as 237 * the vector will not attempt to free the memory itself. 238 * 239 * Once a vector wraps another buffer, it cannot be resized except through 240 * another call to wrap(). However, elements can be erased to make room for 241 * adding new elements. 242 * 243 * Destruction of elements within a wrapped array remains the responsibility 244 * of the calling code. While the vector may invoke the element destructor as 245 * a result of explicit calls to functions like erase() or clear(), it will 246 * not destruct elements remaining in the array when the vector is destructed. 247 * Therefore, special care must be taken when wrapping an array of elements 248 * that have a non-trivial destructor. 249 * 250 * @param array Pointer to a pre-allocated array 251 * @param elementCount Number of elements in the array (NOT the array's size 252 * in bytes); will become the vector's size() and capacity() 253 */ 254 void wrap(ElementType *array, size_t elementCount); 255 256 257 /** 258 * Returns a vector that is wrapping an array to the newly-constructed state, 259 * with capacity equal to 0, and owns_data() is true. 260 */ 261 void unwrap(); 262 263 /** 264 * @return false if this vector is wrapping an array passed in via wrap() 265 */ 266 bool owns_data() const; 267 268 /** 269 * Returns a reference to the first element in the vector. It is illegal to 270 * call this on an empty vector. 271 * 272 * @return The first element in the vector. 273 */ 274 ElementType& front(); 275 276 /** 277 * Returns a const reference to the first element in the vector. It is illegal 278 * to call this on an empty vector. 279 * 280 * @return The first element in the vector. 281 */ 282 const ElementType& front() const; 283 284 /** 285 * Returns a reference to the last element in the vector. It is illegal to 286 * call this on an empty vector. 287 * 288 * @return The last element in the vector. 289 */ 290 ElementType& back(); 291 292 /** 293 * Returns a const reference to the last element in the vector. It is illegal 294 * to call this on an empty vector. 295 * 296 * @return The last element in the vector. 297 */ 298 const ElementType& back() const; 299 300 /** 301 * Prepares a vector to push a minimum of one element onto the back. The 302 * vector may be resized if required. The capacity of the vector increases 303 * with the growth policy of this vector (doubles for each resize for now). 304 * 305 * @return Whether or not the resize was successful. 306 */ 307 bool prepareForPush(); 308 309 /** 310 * Random-access iterator that points to some element in the container. 311 */ 312 typedef ElementType* iterator; 313 typedef const ElementType* const_iterator; 314 315 /** 316 * @return A random-access iterator to the beginning. 317 */ 318 typename DynamicVector<ElementType>::iterator begin(); 319 typename DynamicVector<ElementType>::const_iterator begin() const; 320 typename DynamicVector<ElementType>::const_iterator cbegin() const; 321 322 /** 323 * @return A random-access iterator to the end. 324 */ 325 typename DynamicVector<ElementType>::iterator end(); 326 typename DynamicVector<ElementType>::const_iterator end() const; 327 typename DynamicVector<ElementType>::const_iterator cend() const; 328 329 private: 330 //! A pointer to the underlying data buffer. 331 ElementType *mData = nullptr; 332 333 //! The current size of the vector, as in the number of elements stored. 334 size_t mSize = 0; 335 336 //! The current capacity of the vector, as in the maximum number of elements 337 //! that can be stored. 338 size_t mCapacity = 0; 339 340 //! Set to true when the buffer (mData) was supplied via wrap() 341 bool mDataIsWrapped = false; 342 343 /** 344 * Prepares the vector for insertion - upon successful return, the memory at 345 * the given index will be allocated but uninitialized 346 * 347 * @param index 348 * @return true 349 */ 350 bool prepareInsert(size_t index); 351 }; 352 353 } // namespace chre 354 355 #include "chre/util/dynamic_vector_impl.h" 356 357 #endif // CHRE_UTIL_DYNAMIC_VECTOR_H_ 358