content: /*
   * 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.
   */
  package org.apache.arrow.tools;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import org.apache.arrow.memory.BufferAllocator;
  import org.apache.arrow.memory.RootAllocator;
  import org.apache.arrow.vector.VectorSchemaRoot;
  import org.apache.arrow.vector.ipc.ArrowFileReader;
  import org.apache.arrow.vector.ipc.ArrowStreamWriter;
  
  /**
   * Converts an Arrow file to an Arrow stream. The file should be specified as the first argument and
   * the output is written to standard out.
   */
  public class FileToStream {
    private FileToStream() {}
  
    /** Reads an Arrow file from in and writes it back to out. */
    public static void convert(FileInputStream in, OutputStream out) throws IOException {
      BufferAllocator allocator = new RootAllocator(Integer.MAX_VALUE);
      try (ArrowFileReader reader = new ArrowFileReader(in.getChannel(), allocator)) {
        VectorSchemaRoot root = reader.getVectorSchemaRoot();
        // load the first batch before instantiating the writer so that we have any dictionaries
        // only writeBatches if we loaded one in the first place.
        boolean writeBatches = reader.loadNextBatch();
        try (ArrowStreamWriter writer = new ArrowStreamWriter(root, reader, out)) {
          writer.start();
          while (writeBatches) {
            writer.writeBatch();
            if (!reader.loadNextBatch()) {
              break;
            }
          }
          writer.end();
        }
      }
    }
  
    /**
     * Main method. The first arg is the file path. The second, optional argument, is an output file
     * location (defaults to standard out).
     */
    public static void main(String[] args) throws IOException {
      if (args.length != 1 && args.length != 2) {
        System.err.println("Usage: FileToStream <input file> [output file]");
        System.exit(1);
      }
  
      FileInputStream in = new FileInputStream(new File(args[0]));
      OutputStream out = args.length == 1 ? System.out : new FileOutputStream(new File(args[1]));
  
      convert(in, out);
    }
  }
  