Igor Murashkin | aaebaa0 | 2015-01-26 10:55:53 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2015 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_VARIANT_MAP_H_ |
| 18 | #define ART_RUNTIME_BASE_VARIANT_MAP_H_ |
| 19 | |
| 20 | #include <memory.h> |
| 21 | #include <map> |
| 22 | #include <utility> |
| 23 | |
| 24 | namespace art { |
| 25 | |
| 26 | // |
| 27 | // A variant map is a heterogenous, type safe key->value map. It allows |
| 28 | // for multiple different value types to be stored dynamically in the same map. |
| 29 | // |
| 30 | // It provides the following interface in a nutshell: |
| 31 | // |
| 32 | // struct VariantMap { |
| 33 | // template <typename TValue> |
| 34 | // TValue* Get(Key<T> key); // nullptr if the value was never set, otherwise the value. |
| 35 | // |
| 36 | // template <typename TValue> |
| 37 | // void Set(Key<T> key, TValue value); |
| 38 | // }; |
| 39 | // |
| 40 | // Since the key is strongly typed at compile-time, it is impossible to accidentally |
| 41 | // read/write a value with a different type than the key at either compile-time or run-time. |
| 42 | // |
| 43 | // Do not use VariantMap/VariantMapKey directly. Instead subclass each of them and use |
| 44 | // the subclass, for example: |
| 45 | // |
| 46 | // template <typename TValue> |
| 47 | // struct FruitMapKey : VariantMapKey<TValue> { |
| 48 | // FruitMapKey() {} |
| 49 | // }; |
| 50 | // |
| 51 | // struct FruitMap : VariantMap<FruitMap, FruitMapKey> { |
| 52 | // // This 'using' line is necessary to inherit the variadic constructor. |
| 53 | // using VariantMap<FruitMap, FruitMapKey>::VariantMap; |
| 54 | // |
| 55 | // // Make the next '4' usages of Key slightly shorter to type. |
| 56 | // template <typename TValue> |
| 57 | // using Key = FruitMapKey<TValue>; |
| 58 | // |
| 59 | // static const Key<int> Apple; |
| 60 | // static const Key<double> Orange; |
| 61 | // static const Key<std::string> Banana; |
| 62 | // }; |
| 63 | // |
| 64 | // const FruitMap::Key<int> FruitMap::Apple; |
| 65 | // const FruitMap::Key<double> FruitMap::Orange; |
| 66 | // const FruitMap::Key<std::string> Banana; |
| 67 | // |
| 68 | // See variant_map_test.cc for more examples. |
| 69 | // |
| 70 | |
| 71 | // Implementation details for VariantMap. |
| 72 | namespace detail { |
| 73 | // Allocate a unique counter value each time it's called. |
| 74 | struct VariantMapKeyCounterAllocator { |
| 75 | static size_t AllocateCounter() { |
| 76 | static size_t counter = 0; |
| 77 | counter++; |
| 78 | |
| 79 | return counter; |
| 80 | } |
| 81 | }; |
| 82 | |
| 83 | // Type-erased version of VariantMapKey<T> |
| 84 | struct VariantMapKeyRaw { |
| 85 | // TODO: this may need to call a virtual function to support string comparisons |
| 86 | bool operator<(const VariantMapKeyRaw& other) const { |
| 87 | return key_counter_ < other.key_counter_; |
| 88 | } |
| 89 | |
| 90 | // The following functions need to be virtual since we don't know the compile-time type anymore: |
| 91 | |
| 92 | // Clone the key, creating a copy of the contents. |
| 93 | virtual VariantMapKeyRaw* Clone() const = 0; |
| 94 | |
| 95 | // Delete a value whose runtime type is that of the non-erased key's TValue. |
| 96 | virtual void ValueDelete(void* value) const = 0; |
| 97 | |
| 98 | // Clone a value whose runtime type is that of the non-erased key's TValue. |
| 99 | virtual void* ValueClone(void* value) const = 0; |
| 100 | |
| 101 | // Compare one key to another (same as operator<). |
| 102 | virtual bool Compare(const VariantMapKeyRaw* other) const { |
| 103 | if (other == nullptr) { |
| 104 | return false; |
| 105 | } |
| 106 | return key_counter_ < other->key_counter_; |
| 107 | } |
| 108 | |
| 109 | virtual ~VariantMapKeyRaw() {} |
| 110 | |
| 111 | protected: |
| 112 | VariantMapKeyRaw() |
| 113 | : key_counter_(VariantMapKeyCounterAllocator::AllocateCounter()) {} |
| 114 | // explicit VariantMapKeyRaw(size_t counter) |
| 115 | // : key_counter_(counter) {} |
| 116 | |
| 117 | size_t GetCounter() const { |
| 118 | return key_counter_; |
| 119 | } |
| 120 | |
| 121 | protected: |
| 122 | // Avoid the object slicing problem; use Clone() instead. |
Andreas Gampe | c801f0d | 2015-02-24 20:55:16 -0800 | [diff] [blame] | 123 | VariantMapKeyRaw(const VariantMapKeyRaw&) = default; |
| 124 | VariantMapKeyRaw(VariantMapKeyRaw&&) = default; |
Igor Murashkin | aaebaa0 | 2015-01-26 10:55:53 -0800 | [diff] [blame] | 125 | |
| 126 | private: |
| 127 | size_t key_counter_; // Runtime type ID. Unique each time a new type is reified. |
| 128 | }; |
| 129 | } // namespace detail |
| 130 | |
| 131 | // The base type for keys used by the VariantMap. Users must subclass this type. |
| 132 | template <typename TValue> |
| 133 | struct VariantMapKey : detail::VariantMapKeyRaw { |
| 134 | // Instantiate a default value for this key. If an explicit default value was provided |
| 135 | // then that is used. Otherwise, the default value for the type TValue{} is returned. |
| 136 | TValue CreateDefaultValue() const { |
| 137 | if (default_value_ == nullptr) { |
| 138 | return TValue{}; // NOLINT [readability/braces] [4] |
| 139 | } else { |
| 140 | return TValue(*default_value_); |
| 141 | } |
| 142 | } |
| 143 | |
| 144 | protected: |
| 145 | // explicit VariantMapKey(size_t counter) : detail::VariantMapKeyRaw(counter) {} |
| 146 | explicit VariantMapKey(const TValue& default_value) |
| 147 | : default_value_(std::make_shared<TValue>(default_value)) {} |
| 148 | explicit VariantMapKey(TValue&& default_value) |
| 149 | : default_value_(std::make_shared<TValue>(default_value)) {} |
| 150 | VariantMapKey() {} |
| 151 | virtual ~VariantMapKey() {} |
| 152 | |
| 153 | private: |
| 154 | virtual VariantMapKeyRaw* Clone() const { |
| 155 | return new VariantMapKey<TValue>(*this); |
| 156 | } |
| 157 | |
| 158 | virtual void* ValueClone(void* value) const { |
| 159 | if (value == nullptr) { |
| 160 | return nullptr; |
| 161 | } |
| 162 | |
| 163 | TValue* strong_value = reinterpret_cast<TValue*>(value); |
| 164 | return new TValue(*strong_value); |
| 165 | } |
| 166 | |
| 167 | virtual void ValueDelete(void* value) const { |
| 168 | if (value == nullptr) { |
| 169 | return; |
| 170 | } |
| 171 | |
| 172 | // Smartly invoke the proper delete/delete[]/etc |
| 173 | const std::default_delete<TValue> deleter = std::default_delete<TValue>(); |
| 174 | deleter(reinterpret_cast<TValue*>(value)); |
| 175 | } |
| 176 | |
Andreas Gampe | c801f0d | 2015-02-24 20:55:16 -0800 | [diff] [blame] | 177 | VariantMapKey(const VariantMapKey&) = default; |
| 178 | VariantMapKey(VariantMapKey&&) = default; |
Igor Murashkin | aaebaa0 | 2015-01-26 10:55:53 -0800 | [diff] [blame] | 179 | |
| 180 | template <typename Base, template <typename TV> class TKey> friend struct VariantMap; |
| 181 | |
| 182 | // Store a prototype of the key's default value, for usage with VariantMap::GetOrDefault |
| 183 | std::shared_ptr<TValue> default_value_; |
| 184 | }; |
| 185 | |
| 186 | // Implementation details for a stringified VariantMapStringKey. |
| 187 | namespace detail { |
| 188 | struct VariantMapStringKeyRegistry { |
| 189 | // TODO |
| 190 | }; |
| 191 | } // namespace detail |
| 192 | |
| 193 | // Alternative base type for all keys used by VariantMap, supports runtime strings as the name. |
| 194 | template <typename TValue> |
| 195 | struct VariantMapStringKey : VariantMapKey<TValue> { |
| 196 | explicit VariantMapStringKey(const char* name) |
| 197 | : // VariantMapKey(/*std::hash<std::string>()(name)*/), |
| 198 | name_(name) { |
| 199 | } |
| 200 | |
| 201 | private: |
| 202 | const char* name_; |
| 203 | }; |
| 204 | |
| 205 | // A variant map allows type-safe heteregeneous key->value mappings. |
| 206 | // All possible key types must be specified at compile-time. Values may be added/removed |
| 207 | // at runtime. |
| 208 | template <typename Base, template <typename TV> class TKey> |
| 209 | struct VariantMap { |
| 210 | // Allow users of this static interface to use the key type. |
| 211 | template <typename TValue> |
| 212 | using Key = TKey<TValue>; |
| 213 | |
| 214 | // Look up the value from the key. The pointer becomes invalid if this key is overwritten/removed. |
| 215 | // A null value is returned only when the key does not exist in this map. |
| 216 | template <typename TValue> |
| 217 | const TValue* Get(const TKey<TValue>& key) const { |
| 218 | return GetValuePtr(key); |
| 219 | } |
| 220 | |
| 221 | // Look up the value from the key. The pointer becomes invalid if this key is overwritten/removed. |
| 222 | // A null value is returned only when the key does not exist in this map. |
| 223 | template <typename TValue> |
| 224 | TValue* Get(const TKey<TValue>& key) { |
| 225 | return GetValuePtr(key); |
| 226 | } |
| 227 | |
| 228 | // Lookup the value from the key. If it was not set in the map, return the default value. |
| 229 | // The default value is either the key's default, or TValue{} if the key doesn't have a default. |
| 230 | template <typename TValue> |
| 231 | TValue GetOrDefault(const TKey<TValue>& key) const { |
| 232 | auto* ptr = Get(key); |
| 233 | return (ptr == nullptr) ? key.CreateDefaultValue() : *ptr; |
| 234 | } |
| 235 | |
| 236 | private: |
| 237 | // TODO: move to detail, or make it more generic like a ScopeGuard(function) |
| 238 | template <typename TValue> |
| 239 | struct ScopedRemove { |
| 240 | ScopedRemove(VariantMap& map, const TKey<TValue>& key) : map_(map), key_(key) {} |
| 241 | ~ScopedRemove() { |
| 242 | map_.Remove(key_); |
| 243 | } |
| 244 | |
| 245 | VariantMap& map_; |
| 246 | const TKey<TValue>& key_; |
| 247 | }; |
| 248 | |
| 249 | public: |
| 250 | // Release the value from the key. If it was not set in the map, returns the default value. |
| 251 | // If the key was set, it is removed as a side effect. |
| 252 | template <typename TValue> |
| 253 | TValue ReleaseOrDefault(const TKey<TValue>& key) { |
| 254 | ScopedRemove<TValue> remove_on_return(*this, key); |
| 255 | |
| 256 | TValue* ptr = Get(key); |
| 257 | if (ptr != nullptr) { |
| 258 | return std::move(*ptr); |
| 259 | } else { |
| 260 | TValue default_value = key.CreateDefaultValue(); |
| 261 | return std::move(default_value); |
| 262 | } |
| 263 | } |
| 264 | |
| 265 | // See if a value is stored for this key. |
| 266 | template <typename TValue> |
| 267 | bool Exists(const TKey<TValue>& key) const { |
| 268 | return GetKeyValueIterator(key) != storage_map_.end(); |
| 269 | } |
| 270 | |
| 271 | // Set a value for a given key, overwriting the previous value if any. |
| 272 | template <typename TValue> |
| 273 | void Set(const TKey<TValue>& key, const TValue& value) { |
Igor Murashkin | 2798da1 | 2015-02-06 17:59:39 -0800 | [diff] [blame] | 274 | // Clone the value first, to protect against &value == GetValuePtr(key). |
| 275 | auto* new_value = new TValue(value); |
| 276 | |
Igor Murashkin | aaebaa0 | 2015-01-26 10:55:53 -0800 | [diff] [blame] | 277 | Remove(key); |
Igor Murashkin | 2798da1 | 2015-02-06 17:59:39 -0800 | [diff] [blame] | 278 | storage_map_.insert({{key.Clone(), new_value}}); |
Igor Murashkin | aaebaa0 | 2015-01-26 10:55:53 -0800 | [diff] [blame] | 279 | } |
| 280 | |
| 281 | // Set a value for a given key, only if there was no previous value before. |
| 282 | // Returns true if the value was set, false if a previous value existed. |
| 283 | template <typename TValue> |
| 284 | bool SetIfMissing(const TKey<TValue>& key, const TValue& value) { |
| 285 | TValue* ptr = Get(key); |
| 286 | if (ptr == nullptr) { |
| 287 | Set(key, value); |
| 288 | return true; |
| 289 | } |
| 290 | return false; |
| 291 | } |
| 292 | |
| 293 | // Remove the value for a given key, or a no-op if there was no previously set value. |
| 294 | template <typename TValue> |
| 295 | void Remove(const TKey<TValue>& key) { |
| 296 | StaticAssertKeyType<TValue>(); |
| 297 | |
| 298 | auto&& it = GetKeyValueIterator(key); |
| 299 | if (it != storage_map_.end()) { |
| 300 | key.ValueDelete(it->second); |
| 301 | delete it->first; |
| 302 | storage_map_.erase(it); |
| 303 | } |
| 304 | } |
| 305 | |
| 306 | // Remove all key/value pairs. |
| 307 | void Clear() { |
| 308 | DeleteStoredValues(); |
| 309 | storage_map_.clear(); |
| 310 | } |
| 311 | |
| 312 | // How many key/value pairs are stored in this map. |
| 313 | size_t Size() const { |
| 314 | return storage_map_.size(); |
| 315 | } |
| 316 | |
| 317 | // Construct an empty map. |
| 318 | explicit VariantMap() {} |
| 319 | |
| 320 | template <typename ... TKeyValue> |
| 321 | explicit VariantMap(const TKeyValue& ... key_value_list) { |
| 322 | static_assert(sizeof...(TKeyValue) % 2 == 0, "Must be an even number of key/value elements"); |
| 323 | InitializeParameters(key_value_list...); |
| 324 | } |
| 325 | |
| 326 | // Create a new map from an existing map, copying all the key/value pairs. |
| 327 | VariantMap(const VariantMap& other) { |
| 328 | operator=(other); |
| 329 | } |
| 330 | |
| 331 | // Copy the key/value pairs from the other map into this one. Existing key/values are cleared. |
| 332 | VariantMap& operator=(const VariantMap& other) { |
| 333 | if (this == &other) { |
| 334 | return *this; |
| 335 | } |
| 336 | |
| 337 | Clear(); |
| 338 | |
| 339 | for (auto&& kv_pair : other.storage_map_) { |
| 340 | const detail::VariantMapKeyRaw* raw_key_other = kv_pair.first; |
| 341 | void* value = kv_pair.second; |
| 342 | |
| 343 | detail::VariantMapKeyRaw* cloned_raw_key = raw_key_other->Clone(); |
| 344 | void* cloned_value = raw_key_other->ValueClone(value); |
| 345 | |
| 346 | storage_map_.insert({{ cloned_raw_key, cloned_value }}); |
| 347 | } |
| 348 | |
| 349 | return *this; |
| 350 | } |
| 351 | |
| 352 | // Create a new map by moving an existing map into this one. The other map becomes empty. |
| 353 | VariantMap(VariantMap&& other) { |
| 354 | operator=(std::forward<VariantMap>(other)); |
| 355 | } |
| 356 | |
| 357 | // Move the existing map's key/value pairs into this one. The other map becomes empty. |
| 358 | VariantMap& operator=(VariantMap&& other) { |
| 359 | if (this != &other) { |
| 360 | Clear(); |
| 361 | storage_map_.swap(other.storage_map_); |
| 362 | other.storage_map_.clear(); |
| 363 | } |
| 364 | return *this; |
| 365 | } |
| 366 | |
| 367 | ~VariantMap() { |
| 368 | DeleteStoredValues(); |
| 369 | } |
| 370 | |
| 371 | private: |
| 372 | void InitializeParameters() {} |
| 373 | |
| 374 | template <typename TK, typename TValue, typename ... Rest> |
| 375 | void InitializeParameters(const TK& key, const TValue& value, const Rest& ... rest) { |
| 376 | static_assert( |
| 377 | std::is_same<TK, TKey<TValue>>::value, "The 0th/2nd/4th/etc parameters must be a key"); |
| 378 | |
| 379 | const TKey<TValue>& key_refined = key; |
| 380 | |
| 381 | Set(key_refined, value); |
| 382 | InitializeParameters(rest...); |
| 383 | } |
| 384 | |
| 385 | // Custom key comparator for std::map, needed since we are storing raw pointers as the keys. |
| 386 | struct KeyComparator { |
| 387 | bool operator()(const detail::VariantMapKeyRaw* lhs, |
| 388 | const detail::VariantMapKeyRaw* rhs) const { |
| 389 | if (lhs == nullptr) { |
| 390 | return lhs != rhs; |
| 391 | } |
| 392 | |
| 393 | return lhs->Compare(rhs); |
| 394 | } |
| 395 | }; |
| 396 | |
| 397 | // Map of key pointers to value pointers. Pointers are never null. |
| 398 | using StorageMap = std::map<const detail::VariantMapKeyRaw*, void*, KeyComparator>; |
| 399 | |
| 400 | template <typename TValue> |
| 401 | typename StorageMap::iterator GetKeyValueIterator(const TKey<TValue>& key) { |
| 402 | StaticAssertKeyType<TValue>(); |
| 403 | |
| 404 | const TKey<TValue>* key_ptr = &key; |
| 405 | const detail::VariantMapKeyRaw* raw_ptr = key_ptr; |
| 406 | return storage_map_.find(raw_ptr); |
| 407 | } |
| 408 | |
| 409 | template <typename TValue> |
| 410 | typename StorageMap::const_iterator GetKeyValueIterator(const TKey<TValue>& key) const { |
| 411 | StaticAssertKeyType<TValue>(); |
| 412 | |
| 413 | const TKey<TValue>* key_ptr = &key; |
| 414 | const detail::VariantMapKeyRaw* raw_ptr = key_ptr; |
| 415 | return storage_map_.find(raw_ptr); |
| 416 | } |
| 417 | |
| 418 | template <typename TValue> |
| 419 | TValue* GetValuePtr(const TKey<TValue>& key) { |
| 420 | return const_cast<TValue*>(GetValueConstPtr(key)); |
| 421 | } |
| 422 | |
| 423 | template <typename TValue> |
| 424 | const TValue* GetValuePtr(const TKey<TValue>& key) const { |
| 425 | return GetValueConstPtr(key); |
| 426 | } |
| 427 | |
| 428 | template <typename TValue> |
| 429 | const TValue* GetValueConstPtr(const TKey<TValue>& key) const { |
| 430 | auto&& it = GetKeyValueIterator(key); |
| 431 | if (it == storage_map_.end()) { |
| 432 | return nullptr; |
| 433 | } |
| 434 | |
| 435 | return reinterpret_cast<const TValue*>(it->second); |
| 436 | } |
| 437 | |
| 438 | template <typename TValue> |
| 439 | static void StaticAssertKeyType() { |
| 440 | static_assert(std::is_base_of<VariantMapKey<TValue>, TKey<TValue>>::value, |
| 441 | "The provided key type (TKey) must be a subclass of VariantMapKey"); |
| 442 | } |
| 443 | |
| 444 | void DeleteStoredValues() { |
| 445 | for (auto&& kv_pair : storage_map_) { |
| 446 | kv_pair.first->ValueDelete(kv_pair.second); |
| 447 | delete kv_pair.first; |
| 448 | } |
| 449 | } |
| 450 | |
| 451 | StorageMap storage_map_; |
| 452 | }; |
| 453 | |
| 454 | } // namespace art |
| 455 | |
| 456 | #endif // ART_RUNTIME_BASE_VARIANT_MAP_H_ |