text: // Licensed to the Apache Software Foundation (ASF) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The ASF licenses this file
  // to you under the Apache License, Version 2.0 (the
  // "License"); you may not use this file except in compliance
  // with the License.  You may obtain a copy of the License at
  //
  //   http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing,
  // software distributed under the License is distributed on an
  // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  // KIND, either express or implied.  See the License for the
  // specific language governing permissions and limitations
  // under the License.
  
  #ifndef ARROW_UTIL_KEY_VALUE_METADATA_H
  #define ARROW_UTIL_KEY_VALUE_METADATA_H
  
  #include <cstdint>
  #include <memory>
  #include <string>
  #include <unordered_map>
  #include <utility>
  #include <vector>
  
  #include "arrow/util/macros.h"
  #include "arrow/util/visibility.h"
  
  namespace arrow {
  
  /// \brief A container for key-value pair type metadata. Not thread-safe
  class ARROW_EXPORT KeyValueMetadata {
   public:
    KeyValueMetadata();
    KeyValueMetadata(std::vector<std::string> keys, std::vector<std::string> values);
    explicit KeyValueMetadata(const std::unordered_map<std::string, std::string>& map);
    virtual ~KeyValueMetadata() = default;
  
    void ToUnorderedMap(std::unordered_map<std::string, std::string>* out) const;
  
    void Append(const std::string& key, const std::string& value);
  
    void reserve(int64_t n);
    int64_t size() const;
  
    const std::string& key(int64_t i) const;
    const std::string& value(int64_t i) const;
    std::vector<std::pair<std::string, std::string>> sorted_pairs() const;
  
    /// \brief Perform linear search for key, returning -1 if not found
    int FindKey(const std::string& key) const;
  
    std::shared_ptr<KeyValueMetadata> Copy() const;
  
    /// \brief Return a new KeyValueMetadata by combining the passed metadata
    /// with this KeyValueMetadata. Colliding keys will be overridden by the
    /// passed metadata. Assumes keys in both containers are unique
    std::shared_ptr<KeyValueMetadata> Merge(const KeyValueMetadata& other) const;
  
    bool Equals(const KeyValueMetadata& other) const;
    std::string ToString() const;
  
   private:
    std::vector<std::string> keys_;
    std::vector<std::string> values_;
  
    ARROW_DISALLOW_COPY_AND_ASSIGN(KeyValueMetadata);
  };
  
  /// \brief Create a KeyValueMetadata instance
  ///
  /// \param pairs key-value mapping
  std::shared_ptr<KeyValueMetadata> ARROW_EXPORT
  key_value_metadata(const std::unordered_map<std::string, std::string>& pairs);
  
  /// \brief Create a KeyValueMetadata instance
  ///
  /// \param keys sequence of metadata keys
  /// \param values sequence of corresponding metadata values
  std::shared_ptr<KeyValueMetadata> ARROW_EXPORT key_value_metadata(
      const std::vector<std::string>& keys, const std::vector<std::string>& values);
  
  }  // namespace arrow
  
  #endif  //  ARROW_UTIL_KEY_VALUE_METADATA_H
  