ceph/src/arrow/cpp/src/arrow/util/concurrent_map.h

   1 // Licensed to the Apache Software Foundation (ASF) under one
   2 // or more contributor license agreements.  See the NOTICE file
   3 // distributed with this work for additional information
   4 // regarding copyright ownership.  The ASF licenses this file
   5 // to you under the Apache License, Version 2.0 (the
   6 // "License"); you may not use this file except in compliance
   7 // with the License.  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,
  12 // software distributed under the License is distributed on an
  13 // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  14 // KIND, either express or implied.  See the License for the
  15 // specific language governing permissions and limitations
  16 // under the License.
  17
  18 #pragma once
  19
  20 #include <unordered_map>
  21 #include <utility>
  22
  23 #include "arrow/util/mutex.h"
  24
  25 namespace arrow {
  26 namespace util {
  27
  28 template <typename K, typename V>
  29 class ConcurrentMap {
  30  public:
  31   void Insert(const K& key, const V& value) {
  32     auto lock = mutex_.Lock();
  33     map_.insert({key, value});
  34   }
  35
  36   template <typename ValueFunc>
  37   V GetOrInsert(const K& key, ValueFunc&& compute_value_func) {
  38     auto lock = mutex_.Lock();
  39     auto it = map_.find(key);
  40     if (it == map_.end()) {
  41       auto pair = map_.emplace(key, compute_value_func());
  42       it = pair.first;
  43     }
  44     return it->second;
  45   }
  46
  47   void Erase(const K& key) {
  48     auto lock = mutex_.Lock();
  49     map_.erase(key);
  50   }
  51
  52   void Clear() {
  53     auto lock = mutex_.Lock();
  54     map_.clear();
  55   }
  56
  57   size_t size() const {
  58     auto lock = mutex_.Lock();
  59     return map_.size();
  60   }
  61
  62  private:
  63   std::unordered_map<K, V> map_;
  64   mutable arrow::util::Mutex mutex_;
  65 };
  66
  67 }  // namespace util
  68 }  // namespace arrow