James Robinson | 646469d | 2014-10-03 15:33:28 -0700 | [diff] [blame] | 1 | // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef BASE_ID_MAP_H_ |
| 6 | #define BASE_ID_MAP_H_ |
| 7 | |
| 8 | #include <set> |
| 9 | |
| 10 | #include "base/basictypes.h" |
| 11 | #include "base/containers/hash_tables.h" |
| 12 | #include "base/logging.h" |
| 13 | #include "base/threading/non_thread_safe.h" |
| 14 | |
| 15 | // Ownership semantics - own pointer means the pointer is deleted in Remove() |
| 16 | // & during destruction |
| 17 | enum IDMapOwnershipSemantics { |
| 18 | IDMapExternalPointer, |
| 19 | IDMapOwnPointer |
| 20 | }; |
| 21 | |
| 22 | // This object maintains a list of IDs that can be quickly converted to |
| 23 | // pointers to objects. It is implemented as a hash table, optimized for |
| 24 | // relatively small data sets (in the common case, there will be exactly one |
| 25 | // item in the list). |
| 26 | // |
| 27 | // Items can be inserted into the container with arbitrary ID, but the caller |
| 28 | // must ensure they are unique. Inserting IDs and relying on automatically |
| 29 | // generated ones is not allowed because they can collide. |
| 30 | // |
| 31 | // This class does not have a virtual destructor, do not inherit from it when |
| 32 | // ownership semantics are set to own because pointers will leak. |
| 33 | template<typename T, IDMapOwnershipSemantics OS = IDMapExternalPointer> |
| 34 | class IDMap : public base::NonThreadSafe { |
| 35 | public: |
| 36 | typedef int32 KeyType; |
| 37 | |
| 38 | private: |
| 39 | typedef base::hash_map<KeyType, T*> HashTable; |
| 40 | |
| 41 | public: |
| 42 | IDMap() : iteration_depth_(0), next_id_(1), check_on_null_data_(false) { |
| 43 | // A number of consumers of IDMap create it on one thread but always access |
| 44 | // it from a different, but consitent, thread post-construction. |
| 45 | DetachFromThread(); |
| 46 | } |
| 47 | |
| 48 | ~IDMap() { |
| 49 | // Many IDMap's are static, and hence will be destroyed on the main thread. |
| 50 | // However, all the accesses may take place on another thread, such as the |
| 51 | // IO thread. Detaching again to clean this up. |
| 52 | DetachFromThread(); |
| 53 | Releaser<OS, 0>::release_all(&data_); |
| 54 | } |
| 55 | |
Przemyslaw Pietrzkiewicz | ea77f0b | 2014-12-10 15:35:08 +0100 | [diff] [blame] | 56 | // Sets whether Add and Replace should DCHECK if passed in NULL data. |
| 57 | // Default is false. |
James Robinson | 646469d | 2014-10-03 15:33:28 -0700 | [diff] [blame] | 58 | void set_check_on_null_data(bool value) { check_on_null_data_ = value; } |
| 59 | |
| 60 | // Adds a view with an automatically generated unique ID. See AddWithID. |
| 61 | KeyType Add(T* data) { |
| 62 | DCHECK(CalledOnValidThread()); |
Przemyslaw Pietrzkiewicz | ea77f0b | 2014-12-10 15:35:08 +0100 | [diff] [blame] | 63 | DCHECK(!check_on_null_data_ || data); |
James Robinson | 646469d | 2014-10-03 15:33:28 -0700 | [diff] [blame] | 64 | KeyType this_id = next_id_; |
| 65 | DCHECK(data_.find(this_id) == data_.end()) << "Inserting duplicate item"; |
| 66 | data_[this_id] = data; |
| 67 | next_id_++; |
| 68 | return this_id; |
| 69 | } |
| 70 | |
| 71 | // Adds a new data member with the specified ID. The ID must not be in |
| 72 | // the list. The caller either must generate all unique IDs itself and use |
| 73 | // this function, or allow this object to generate IDs and call Add. These |
| 74 | // two methods may not be mixed, or duplicate IDs may be generated |
| 75 | void AddWithID(T* data, KeyType id) { |
| 76 | DCHECK(CalledOnValidThread()); |
Przemyslaw Pietrzkiewicz | ea77f0b | 2014-12-10 15:35:08 +0100 | [diff] [blame] | 77 | DCHECK(!check_on_null_data_ || data); |
James Robinson | 646469d | 2014-10-03 15:33:28 -0700 | [diff] [blame] | 78 | DCHECK(data_.find(id) == data_.end()) << "Inserting duplicate item"; |
| 79 | data_[id] = data; |
| 80 | } |
| 81 | |
| 82 | void Remove(KeyType id) { |
| 83 | DCHECK(CalledOnValidThread()); |
| 84 | typename HashTable::iterator i = data_.find(id); |
| 85 | if (i == data_.end()) { |
| 86 | NOTREACHED() << "Attempting to remove an item not in the list"; |
| 87 | return; |
| 88 | } |
| 89 | |
| 90 | if (iteration_depth_ == 0) { |
| 91 | Releaser<OS, 0>::release(i->second); |
| 92 | data_.erase(i); |
| 93 | } else { |
| 94 | removed_ids_.insert(id); |
| 95 | } |
| 96 | } |
| 97 | |
Przemyslaw Pietrzkiewicz | ea77f0b | 2014-12-10 15:35:08 +0100 | [diff] [blame] | 98 | // Replaces the value for |id| with |new_data| and returns a pointer to the |
| 99 | // existing value. If there is no entry for |id|, the map is not altered and |
| 100 | // nullptr is returned. The OwnershipSemantics of the map have no effect on |
| 101 | // how the existing value is treated, the IDMap does not delete the existing |
| 102 | // value being replaced. |
| 103 | T* Replace(KeyType id, T* new_data) { |
| 104 | DCHECK(CalledOnValidThread()); |
| 105 | DCHECK(!check_on_null_data_ || new_data); |
| 106 | typename HashTable::iterator i = data_.find(id); |
| 107 | if (i == data_.end()) { |
| 108 | NOTREACHED() << "Attempting to replace an item not in the list"; |
| 109 | return nullptr; |
| 110 | } |
| 111 | |
| 112 | T* temp = i->second; |
| 113 | i->second = new_data; |
| 114 | return temp; |
| 115 | } |
| 116 | |
James Robinson | 646469d | 2014-10-03 15:33:28 -0700 | [diff] [blame] | 117 | void Clear() { |
| 118 | DCHECK(CalledOnValidThread()); |
| 119 | if (iteration_depth_ == 0) { |
| 120 | Releaser<OS, 0>::release_all(&data_); |
| 121 | } else { |
| 122 | for (typename HashTable::iterator i = data_.begin(); |
| 123 | i != data_.end(); ++i) |
| 124 | removed_ids_.insert(i->first); |
| 125 | } |
| 126 | } |
| 127 | |
| 128 | bool IsEmpty() const { |
| 129 | DCHECK(CalledOnValidThread()); |
| 130 | return size() == 0u; |
| 131 | } |
| 132 | |
| 133 | T* Lookup(KeyType id) const { |
| 134 | DCHECK(CalledOnValidThread()); |
| 135 | typename HashTable::const_iterator i = data_.find(id); |
| 136 | if (i == data_.end()) |
| 137 | return NULL; |
| 138 | return i->second; |
| 139 | } |
| 140 | |
| 141 | size_t size() const { |
| 142 | DCHECK(CalledOnValidThread()); |
| 143 | return data_.size() - removed_ids_.size(); |
| 144 | } |
| 145 | |
| 146 | #if defined(UNIT_TEST) |
| 147 | int iteration_depth() const { |
| 148 | return iteration_depth_; |
| 149 | } |
| 150 | #endif // defined(UNIT_TEST) |
| 151 | |
| 152 | // It is safe to remove elements from the map during iteration. All iterators |
| 153 | // will remain valid. |
| 154 | template<class ReturnType> |
| 155 | class Iterator { |
| 156 | public: |
| 157 | Iterator(IDMap<T, OS>* map) |
| 158 | : map_(map), |
| 159 | iter_(map_->data_.begin()) { |
| 160 | Init(); |
| 161 | } |
| 162 | |
| 163 | Iterator(const Iterator& iter) |
| 164 | : map_(iter.map_), |
| 165 | iter_(iter.iter_) { |
| 166 | Init(); |
| 167 | } |
| 168 | |
| 169 | const Iterator& operator=(const Iterator& iter) { |
| 170 | map_ = iter.map; |
| 171 | iter_ = iter.iter; |
| 172 | Init(); |
| 173 | return *this; |
| 174 | } |
| 175 | |
| 176 | ~Iterator() { |
| 177 | DCHECK(map_->CalledOnValidThread()); |
| 178 | |
| 179 | // We're going to decrement iteration depth. Make sure it's greater than |
| 180 | // zero so that it doesn't become negative. |
| 181 | DCHECK_LT(0, map_->iteration_depth_); |
| 182 | |
| 183 | if (--map_->iteration_depth_ == 0) |
| 184 | map_->Compact(); |
| 185 | } |
| 186 | |
| 187 | bool IsAtEnd() const { |
| 188 | DCHECK(map_->CalledOnValidThread()); |
| 189 | return iter_ == map_->data_.end(); |
| 190 | } |
| 191 | |
| 192 | KeyType GetCurrentKey() const { |
| 193 | DCHECK(map_->CalledOnValidThread()); |
| 194 | return iter_->first; |
| 195 | } |
| 196 | |
| 197 | ReturnType* GetCurrentValue() const { |
| 198 | DCHECK(map_->CalledOnValidThread()); |
| 199 | return iter_->second; |
| 200 | } |
| 201 | |
| 202 | void Advance() { |
| 203 | DCHECK(map_->CalledOnValidThread()); |
| 204 | ++iter_; |
| 205 | SkipRemovedEntries(); |
| 206 | } |
| 207 | |
| 208 | private: |
| 209 | void Init() { |
| 210 | DCHECK(map_->CalledOnValidThread()); |
| 211 | ++map_->iteration_depth_; |
| 212 | SkipRemovedEntries(); |
| 213 | } |
| 214 | |
| 215 | void SkipRemovedEntries() { |
| 216 | while (iter_ != map_->data_.end() && |
| 217 | map_->removed_ids_.find(iter_->first) != |
| 218 | map_->removed_ids_.end()) { |
| 219 | ++iter_; |
| 220 | } |
| 221 | } |
| 222 | |
| 223 | IDMap<T, OS>* map_; |
| 224 | typename HashTable::const_iterator iter_; |
| 225 | }; |
| 226 | |
| 227 | typedef Iterator<T> iterator; |
| 228 | typedef Iterator<const T> const_iterator; |
| 229 | |
| 230 | private: |
| 231 | |
| 232 | // The dummy parameter is there because C++ standard does not allow |
| 233 | // explicitly specialized templates inside classes |
| 234 | template<IDMapOwnershipSemantics OI, int dummy> struct Releaser { |
| 235 | static inline void release(T* ptr) {} |
| 236 | static inline void release_all(HashTable* table) {} |
| 237 | }; |
| 238 | |
| 239 | template<int dummy> struct Releaser<IDMapOwnPointer, dummy> { |
| 240 | static inline void release(T* ptr) { delete ptr;} |
| 241 | static inline void release_all(HashTable* table) { |
| 242 | for (typename HashTable::iterator i = table->begin(); |
| 243 | i != table->end(); ++i) { |
| 244 | delete i->second; |
| 245 | } |
| 246 | table->clear(); |
| 247 | } |
| 248 | }; |
| 249 | |
| 250 | void Compact() { |
| 251 | DCHECK_EQ(0, iteration_depth_); |
| 252 | for (std::set<KeyType>::const_iterator i = removed_ids_.begin(); |
| 253 | i != removed_ids_.end(); ++i) { |
| 254 | Remove(*i); |
| 255 | } |
| 256 | removed_ids_.clear(); |
| 257 | } |
| 258 | |
| 259 | // Keep track of how many iterators are currently iterating on us to safely |
| 260 | // handle removing items during iteration. |
| 261 | int iteration_depth_; |
| 262 | |
| 263 | // Keep set of IDs that should be removed after the outermost iteration has |
| 264 | // finished. This way we manage to not invalidate the iterator when an element |
| 265 | // is removed. |
| 266 | std::set<KeyType> removed_ids_; |
| 267 | |
| 268 | // The next ID that we will return from Add() |
| 269 | KeyType next_id_; |
| 270 | |
| 271 | HashTable data_; |
| 272 | |
| 273 | // See description above setter. |
| 274 | bool check_on_null_data_; |
| 275 | |
| 276 | DISALLOW_COPY_AND_ASSIGN(IDMap); |
| 277 | }; |
| 278 | |
| 279 | #endif // BASE_ID_MAP_H_ |