1 /*
2  * Copyright (C) 2013 The Android Open Source Project
3 
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  *      http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17 
18 #include <stddef.h>
19 #include <map>
20 #include <list>
21 
22 #ifndef ART_COMPILER_UTILS_SCOPED_HASHTABLE_H_
23 #define ART_COMPILER_UTILS_SCOPED_HASHTABLE_H_
24 
25 namespace utils {
26 template <typename K, typename V>
27 class ScopedHashtable {
28  public:
ScopedHashtable()29   explicit ScopedHashtable():scopes() {
30   }
31 
OpenScope()32   void OpenScope() {
33     scopes.push_front(std::map<K, V>());
34   }
35 
36   // Lookups entry K starting from the current (topmost) scope
37   // and returns its value if found or NULL.
Lookup(K k)38   V Lookup(K k) const {
39     for (typename std::list<std::map<K, V>>::const_iterator scopes_it = scopes.begin();
40         scopes_it != scopes.end(); scopes_it++) {
41       typename std::map<K, V>::const_iterator result_it = (*scopes_it).find(k);
42       if (result_it != (*scopes_it).end()) {
43         return (*result_it).second;
44       }
45     }
46     return NULL;
47   }
48 
49   // Adds a new entry in the current (topmost) scope.
Add(K k,V v)50   void Add(K k, V v) {
51     scopes.front().erase(k);
52     scopes.front().insert(std::pair< K, V >(k, v));
53   }
54 
55   // Removes the topmost scope.
CloseScope()56   bool CloseScope() {
57     // Added check to uniformly handle undefined behavior
58     // when removing scope and the list of scopes is empty.
59     if (scopes.size() > 0) {
60       scopes.pop_front();
61       return true;
62     }
63     return false;
64   }
65 
66  private:
67   std::list<std::map<K, V>> scopes;
68 };
69 }  // namespace utils
70 
71 #endif  // ART_COMPILER_UTILS_SCOPED_HASHTABLE_H_
72