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.
  
  // This module contains the logical parquet-cpp types (independent of Thrift
  // structures), schema nodes, and related type tools
  
  #ifndef PARQUET_SCHEMA_INTERNAL_H
  #define PARQUET_SCHEMA_INTERNAL_H
  
  #include <cstdint>
  #include <memory>
  #include <vector>
  
  #include "parquet/schema.h"
  #include "parquet/types.h"
  #include "parquet/util/macros.h"
  
  namespace parquet {
  
  namespace format {
  class SchemaElement;
  }
  
  namespace schema {
  
  // ----------------------------------------------------------------------
  // Conversion from Parquet Thrift metadata
  
  std::shared_ptr<SchemaDescriptor> FromParquet(
      const std::vector<format::SchemaElement>& schema);
  
  class FlatSchemaConverter {
   public:
    FlatSchemaConverter(const format::SchemaElement* elements, int length)
        : elements_(elements), length_(length), pos_(0), current_id_(0) {}
  
    std::unique_ptr<Node> Convert();
  
   private:
    const format::SchemaElement* elements_;
    int length_;
    int pos_;
    int current_id_;
  
    int next_id() { return current_id_++; }
  
    const format::SchemaElement& Next();
  
    std::unique_ptr<Node> NextNode();
  };
  
  // ----------------------------------------------------------------------
  // Conversion to Parquet Thrift metadata
  
  void ToParquet(const GroupNode* schema, std::vector<format::SchemaElement>* out);
  
  // Converts nested parquet schema back to a flat vector of Thrift structs
  class SchemaFlattener {
   public:
    SchemaFlattener(const GroupNode* schema, std::vector<format::SchemaElement>* out);
  
    void Flatten();
  
   private:
    const GroupNode* root_;
    std::vector<format::SchemaElement>* elements_;
  };
  
  }  // namespace schema
  }  // namespace parquet
  
  #endif  // PARQUET_SCHEMA_INTERNAL_H
  