safe_map.h revision 83cc7ae96d4176533dd0391a1591d321b0a87f4f 
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>::allocator_type allocator_type;
38  typedef typename ::std::map<K, V, Comparator, Allocator>::iterator iterator;
39  typedef typename ::std::map<K, V, Comparator, Allocator>::const_iterator const_iterator;
40  typedef typename ::std::map<K, V, Comparator, Allocator>::size_type size_type;
41  typedef typename ::std::map<K, V, Comparator, Allocator>::value_type value_type;
42
43  SafeMap() = default;
44  explicit SafeMap(const key_compare& cmp, const allocator_type& allocator = allocator_type())
45    : map_(cmp, allocator) {
46  }
47
48  Self& operator=(const Self& rhs) {
49    map_ = rhs.map_;
50    return *this;
51  }
52
53  iterator begin() { return map_.begin(); }
54  const_iterator begin() const { return map_.begin(); }
55  iterator end() { return map_.end(); }
56  const_iterator end() const { return map_.end(); }
57
58  bool empty() const { return map_.empty(); }
59  size_type size() const { return map_.size(); }
60
61  void clear() { map_.clear(); }
62  void erase(iterator it) { map_.erase(it); }
63  size_type erase(const K& k) { return map_.erase(k); }
64
65  iterator find(const K& k) { return map_.find(k); }
66  const_iterator find(const K& k) const { return map_.find(k); }
67
68  size_type count(const K& k) const { return map_.count(k); }
69
70  // Note that unlike std::map's operator[], this doesn't return a reference to the value.
71  V Get(const K& k) const {
72    const_iterator it = map_.find(k);
73    DCHECK(it != map_.end());
74    return it->second;
75  }
76
77  // Used to insert a new mapping.
78  void Put(const K& k, const V& v) {
79    std::pair<iterator, bool> result = map_.insert(std::make_pair(k, v));
80    DCHECK(result.second);  // Check we didn't accidentally overwrite an existing value.
81  }
82
83  // Used to insert a new mapping or overwrite an existing mapping. Note that if the value type
84  // of this container is a pointer, any overwritten pointer will be lost and if this container
85  // was the owner, you have a leak.
86  void Overwrite(const K& k, const V& v) {
87    std::pair<iterator, bool> result = map_.insert(std::make_pair(k, v));
88    if (!result.second) {
89      // Already there - update the value for the existing key
90      result.first->second = v;
91    }
92  }
93
94  bool Equals(const Self& rhs) const {
95    return map_ == rhs.map_;
96  }
97
98 private:
99  ::std::map<K, V, Comparator, Allocator> map_;
100};
101
102template <typename K, typename V, typename Comparator>
103bool operator==(const SafeMap<K, V, Comparator>& lhs, const SafeMap<K, V, Comparator>& rhs) {
104  return lhs.Equals(rhs);
105}
106
107template <typename K, typename V, typename Comparator>
108bool operator!=(const SafeMap<K, V, Comparator>& lhs, const SafeMap<K, V, Comparator>& rhs) {
109  return !(lhs == rhs);
110}
111
112}  // namespace art
113
114#endif  // ART_RUNTIME_SAFE_MAP_H_
115