1 /*
2  * Copyright (C) 2012 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_SAFE_MAP_H_
18 #define ART_RUNTIME_SAFE_MAP_H_
19 
20 #include <map>
21 #include <memory>
22 #include <type_traits>
23 
24 #include "base/allocator.h"
25 #include "base/logging.h"
26 
27 namespace art {
28 
29 // Equivalent to std::map, but without operator[] and its bug-prone semantics (in particular,
30 // the implicit insertion of a default-constructed value on failed lookups).
31 template <typename K, typename V, typename Comparator = std::less<K>,
32           typename Allocator = TrackingAllocator<std::pair<const K, V>, kAllocatorTagSafeMap>>
33 class SafeMap {
34  private:
35   typedef SafeMap<K, V, Comparator, Allocator> Self;
36 
37  public:
38   typedef typename ::std::map<K, V, Comparator, Allocator>::key_compare key_compare;
39   typedef typename ::std::map<K, V, Comparator, Allocator>::value_compare value_compare;
40   typedef typename ::std::map<K, V, Comparator, Allocator>::allocator_type allocator_type;
41   typedef typename ::std::map<K, V, Comparator, Allocator>::iterator iterator;
42   typedef typename ::std::map<K, V, Comparator, Allocator>::const_iterator const_iterator;
43   typedef typename ::std::map<K, V, Comparator, Allocator>::size_type size_type;
44   typedef typename ::std::map<K, V, Comparator, Allocator>::key_type key_type;
45   typedef typename ::std::map<K, V, Comparator, Allocator>::value_type value_type;
46 
47   SafeMap() = default;
48   SafeMap(const SafeMap&) = default;
49   explicit SafeMap(const key_compare& cmp, const allocator_type& allocator = allocator_type())
map_(cmp,allocator)50     : map_(cmp, allocator) {
51   }
52 
53   Self& operator=(const Self& rhs) {
54     map_ = rhs.map_;
55     return *this;
56   }
57 
get_allocator()58   allocator_type get_allocator() const { return map_.get_allocator(); }
key_comp()59   key_compare key_comp() const { return map_.key_comp(); }
value_comp()60   value_compare value_comp() const { return map_.value_comp(); }
61 
begin()62   iterator begin() { return map_.begin(); }
begin()63   const_iterator begin() const { return map_.begin(); }
end()64   iterator end() { return map_.end(); }
end()65   const_iterator end() const { return map_.end(); }
66 
empty()67   bool empty() const { return map_.empty(); }
size()68   size_type size() const { return map_.size(); }
69 
swap(Self & other)70   void swap(Self& other) { map_.swap(other.map_); }
clear()71   void clear() { map_.clear(); }
erase(iterator it)72   iterator erase(iterator it) { return map_.erase(it); }
erase(const K & k)73   size_type erase(const K& k) { return map_.erase(k); }
74 
find(const K & k)75   iterator find(const K& k) { return map_.find(k); }
find(const K & k)76   const_iterator find(const K& k) const { return map_.find(k); }
77 
lower_bound(const K & k)78   iterator lower_bound(const K& k) { return map_.lower_bound(k); }
lower_bound(const K & k)79   const_iterator lower_bound(const K& k) const { return map_.lower_bound(k); }
80 
count(const K & k)81   size_type count(const K& k) const { return map_.count(k); }
82 
83   // Note that unlike std::map's operator[], this doesn't return a reference to the value.
Get(const K & k)84   V Get(const K& k) const {
85     const_iterator it = map_.find(k);
86     DCHECK(it != map_.end());
87     return it->second;
88   }
89 
90   // Used to insert a new mapping.
Put(const K & k,const V & v)91   iterator Put(const K& k, const V& v) {
92     std::pair<iterator, bool> result = map_.emplace(k, v);
93     DCHECK(result.second);  // Check we didn't accidentally overwrite an existing value.
94     return result.first;
95   }
Put(const K & k,V && v)96   iterator Put(const K& k, V&& v) {
97     std::pair<iterator, bool> result = map_.emplace(k, std::move(v));
98     DCHECK(result.second);  // Check we didn't accidentally overwrite an existing value.
99     return result.first;
100   }
101 
102   // Used to insert a new mapping at a known position for better performance.
PutBefore(const_iterator pos,const K & k,const V & v)103   iterator PutBefore(const_iterator pos, const K& k, const V& v) {
104     // Check that we're using the correct position and the key is not in the map.
105     DCHECK(pos == map_.end() || map_.key_comp()(k, pos->first));
106     DCHECK(pos == map_.begin() || map_.key_comp()((--const_iterator(pos))->first, k));
107     return map_.emplace_hint(pos, k, v);
108   }
PutBefore(const_iterator pos,const K & k,V && v)109   iterator PutBefore(const_iterator pos, const K& k, V&& v) {
110     // Check that we're using the correct position and the key is not in the map.
111     DCHECK(pos == map_.end() || map_.key_comp()(k, pos->first));
112     DCHECK(pos == map_.begin() || map_.key_comp()((--const_iterator(pos))->first, k));
113     return map_.emplace_hint(pos, k, std::move(v));
114   }
115 
116   // Used to insert a new mapping or overwrite an existing mapping. Note that if the value type
117   // of this container is a pointer, any overwritten pointer will be lost and if this container
118   // was the owner, you have a leak. Returns iterator pointing to the new or overwritten entry.
Overwrite(const K & k,const V & v)119   iterator Overwrite(const K& k, const V& v) {
120     std::pair<iterator, bool> result = map_.insert(std::make_pair(k, v));
121     if (!result.second) {
122       // Already there - update the value for the existing key
123       result.first->second = v;
124     }
125     return result.first;
126   }
127 
128   template <typename CreateFn>
GetOrCreate(const K & k,CreateFn create)129   V GetOrCreate(const K& k, CreateFn create) {
130     static_assert(std::is_same<V, typename std::result_of<CreateFn()>::type>::value,
131                   "Argument `create` should return a value of type V.");
132     auto lb = lower_bound(k);
133     if (lb != end() && !key_comp()(k, lb->first)) {
134       return lb->second;
135     }
136     auto it = PutBefore(lb, k, create());
137     return it->second;
138   }
139 
FindOrAdd(const K & k,const V & v)140   iterator FindOrAdd(const K& k, const V& v) {
141     iterator it = find(k);
142     return it == end() ? Put(k, v) : it;
143   }
144 
FindOrAdd(const K & k)145   iterator FindOrAdd(const K& k) {
146     iterator it = find(k);
147     return it == end() ? Put(k, V()) : it;
148   }
149 
Equals(const Self & rhs)150   bool Equals(const Self& rhs) const {
151     return map_ == rhs.map_;
152   }
153 
154  private:
155   ::std::map<K, V, Comparator, Allocator> map_;
156 };
157 
158 template <typename K, typename V, typename Comparator, typename Allocator>
159 bool operator==(const SafeMap<K, V, Comparator, Allocator>& lhs,
160                 const SafeMap<K, V, Comparator, Allocator>& rhs) {
161   return lhs.Equals(rhs);
162 }
163 
164 template <typename K, typename V, typename Comparator, typename Allocator>
165 bool operator!=(const SafeMap<K, V, Comparator, Allocator>& lhs,
166                 const SafeMap<K, V, Comparator, Allocator>& rhs) {
167   return !(lhs == rhs);
168 }
169 
170 template<class Key, class T, AllocatorTag kTag, class Compare = std::less<Key>>
171 class AllocationTrackingSafeMap : public SafeMap<
172     Key, T, Compare, TrackingAllocator<std::pair<const Key, T>, kTag>> {
173 };
174 
175 }  // namespace art
176 
177 #endif  // ART_RUNTIME_SAFE_MAP_H_
178