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      1 /*
      2  * Copyright (C) 2015 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 AAPT_UTIL_IMMUTABLEMAP_H
     18 #define AAPT_UTIL_IMMUTABLEMAP_H
     19 
     20 #include <utility>
     21 #include <vector>
     22 
     23 #include "util/TypeTraits.h"
     24 
     25 namespace aapt {
     26 
     27 template <typename TKey, typename TValue>
     28 class ImmutableMap {
     29   static_assert(is_comparable<TKey, TKey>::value, "key is not comparable");
     30 
     31  public:
     32   using const_iterator =
     33       typename std::vector<std::pair<TKey, TValue>>::const_iterator;
     34 
     35   ImmutableMap(ImmutableMap&&) = default;
     36   ImmutableMap& operator=(ImmutableMap&&) = default;
     37 
     38   static ImmutableMap<TKey, TValue> CreatePreSorted(
     39       std::initializer_list<std::pair<TKey, TValue>> list) {
     40     return ImmutableMap(
     41         std::vector<std::pair<TKey, TValue>>(list.begin(), list.end()));
     42   }
     43 
     44   static ImmutableMap<TKey, TValue> CreateAndSort(
     45       std::initializer_list<std::pair<TKey, TValue>> list) {
     46     std::vector<std::pair<TKey, TValue>> data(list.begin(), list.end());
     47     std::sort(data.begin(), data.end());
     48     return ImmutableMap(std::move(data));
     49   }
     50 
     51   template <typename TKey2, typename = typename std::enable_if<
     52                                 is_comparable<TKey, TKey2>::value>::type>
     53   const_iterator find(const TKey2& key) const {
     54     auto cmp = [](const std::pair<TKey, TValue>& candidate,
     55                   const TKey2& target) -> bool {
     56       return candidate.first < target;
     57     };
     58 
     59     const_iterator end_iter = end();
     60     auto iter = std::lower_bound(data_.begin(), end_iter, key, cmp);
     61     if (iter == end_iter || iter->first == key) {
     62       return iter;
     63     }
     64     return end_iter;
     65   }
     66 
     67   const_iterator begin() const { return data_.begin(); }
     68 
     69   const_iterator end() const { return data_.end(); }
     70 
     71  private:
     72   DISALLOW_COPY_AND_ASSIGN(ImmutableMap);
     73 
     74   explicit ImmutableMap(std::vector<std::pair<TKey, TValue>> data)
     75       : data_(std::move(data)) {}
     76 
     77   std::vector<std::pair<TKey, TValue>> data_;
     78 };
     79 
     80 }  // namespace aapt
     81 
     82 #endif /* AAPT_UTIL_IMMUTABLEMAP_H */
     83