safe_map.h revision b19955d3c8fbd9588f7e17299e559d02938154b6 
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
23#include "base/logging.h"
24
25namespace art {
26
27// Equivalent to std::map, but without operator[] and its bug-prone semantics (in particular,
28// the implicit insertion of a default-constructed value on failed lookups).
29template <typename K, typename V, typename Comparator = std::less<K>,
30          typename Allocator = std::allocator<std::pair<const K, V>>>
31class SafeMap {
32 private:
33  typedef SafeMap<K, V, Comparator, Allocator> Self;
34
35 public:
36  typedef typename ::std::map<K, V, Comparator, Allocator>::key_compare key_compare;
37  typedef typename ::std::map<K, V, Comparator, Allocator>::value_compare value_compare;
38  typedef typename ::std::map<K, V, Comparator, Allocator>::allocator_type allocator_type;
39  typedef typename ::std::map<K, V, Comparator, Allocator>::iterator iterator;
40  typedef typename ::std::map<K, V, Comparator, Allocator>::const_iterator const_iterator;
41  typedef typename ::std::map<K, V, Comparator, Allocator>::size_type size_type;
42  typedef typename ::std::map<K, V, Comparator, Allocator>::key_type key_type;
43  typedef typename ::std::map<K, V, Comparator, Allocator>::value_type value_type;
44
45  SafeMap() = default;
46  explicit SafeMap(const key_compare& cmp, const allocator_type& allocator = allocator_type())
47    : map_(cmp, allocator) {
48  }
49
50  Self& operator=(const Self& rhs) {
51    map_ = rhs.map_;
52    return *this;
53  }
54
55  allocator_type get_allocator() const { return map_.get_allocator(); }
56  key_compare key_comp() const { return map_.key_comp(); }
57  value_compare value_comp() const { return map_.value_comp(); }
58
59  iterator begin() { return map_.begin(); }
60  const_iterator begin() const { return map_.begin(); }
61  iterator end() { return map_.end(); }
62  const_iterator end() const { return map_.end(); }
63
64  bool empty() const { return map_.empty(); }
65  size_type size() const { return map_.size(); }
66
67  void swap(Self& other) { map_.swap(other.map_); }
68  void clear() { map_.clear(); }
69  iterator erase(iterator it) { return map_.erase(it); }
70  size_type erase(const K& k) { return map_.erase(k); }
71
72  iterator find(const K& k) { return map_.find(k); }
73  const_iterator find(const K& k) const { return map_.find(k); }
74
75  iterator lower_bound(const K& k) { return map_.lower_bound(k); }
76  const_iterator lower_bound(const K& k) const { return map_.lower_bound(k); }
77
78  size_type count(const K& k) const { return map_.count(k); }
79
80  // Note that unlike std::map's operator[], this doesn't return a reference to the value.
81  V Get(const K& k) const {
82    const_iterator it = map_.find(k);
83    DCHECK(it != map_.end());
84    return it->second;
85  }
86
87  // Used to insert a new mapping.
88  iterator Put(const K& k, const V& v) {
89    std::pair<iterator, bool> result = map_.emplace(k, v);
90    DCHECK(result.second);  // Check we didn't accidentally overwrite an existing value.
91    return result.first;
92  }
93
94  // Used to insert a new mapping at a known position for better performance.
95  iterator PutBefore(iterator pos, const K& k, const V& v) {
96    // Check that we're using the correct position and the key is not in the map.
97    DCHECK(pos == map_.end() || map_.key_comp()(k, pos->first));
98    DCHECK(pos == map_.begin() || map_.key_comp()((--iterator(pos))->first, k));
99    return map_.emplace_hint(pos, k, v);
100  }
101
102  // Used to insert a new mapping or overwrite an existing mapping. Note that if the value type
103  // of this container is a pointer, any overwritten pointer will be lost and if this container
104  // was the owner, you have a leak.
105  void Overwrite(const K& k, const V& v) {
106    std::pair<iterator, bool> result = map_.insert(std::make_pair(k, v));
107    if (!result.second) {
108      // Already there - update the value for the existing key
109      result.first->second = v;
110    }
111  }
112
113  bool Equals(const Self& rhs) const {
114    return map_ == rhs.map_;
115  }
116
117 private:
118  ::std::map<K, V, Comparator, Allocator> map_;
119};
120
121template <typename K, typename V, typename Comparator, typename Allocator>
122bool operator==(const SafeMap<K, V, Comparator, Allocator>& lhs,
123                const SafeMap<K, V, Comparator, Allocator>& rhs) {
124  return lhs.Equals(rhs);
125}
126
127template <typename K, typename V, typename Comparator, typename Allocator>
128bool operator!=(const SafeMap<K, V, Comparator, Allocator>& lhs,
129                const SafeMap<K, V, Comparator, Allocator>& rhs) {
130  return !(lhs == rhs);
131}
132
133}  // namespace art
134
135#endif  // ART_RUNTIME_SAFE_MAP_H_
136