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Avro command line tools and utilities
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/*
 * 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.avro.tool;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

import org.apache.avro.Schema;
import org.apache.avro.file.CodecFactory;
import org.apache.avro.file.DataFileConstants;
import org.apache.avro.file.DataFileStream;
import org.apache.avro.file.DataFileWriter;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.generic.GenericRecord;
import org.apache.hadoop.fs.Path;

/**
 * Tool to concatenate avro files with the same schema and non-reserved
 * metatdata.
 */
public class ConcatTool implements Tool {
  /**
   * @return 0 for success, 1 if the schemas of the input files differ, 2 if the
   *         non-reserved input metadata differs, 3 if the input files are encoded
   *         with more than one codec.
   */
  @Override
  public int run(InputStream in, PrintStream out, PrintStream err, List args) throws Exception {

    if (args.isEmpty()) {
      printHelp(out);
      return 0;
    }

    OutputStream output = out;
    if (args.size() > 1) {
      output = Util.fileOrStdout(args.get(args.size() - 1), out);
      args = args.subList(0, args.size() - 1);
    }

    DataFileWriter writer = new DataFileWriter<>(new GenericDatumWriter<>());
    Schema schema = null;
    Map metadata = new TreeMap<>();
    String inputCodec = null;

    for (String inFile : expandsInputFiles(args)) {
      InputStream input = Util.fileOrStdin(inFile, in);
      DataFileStream reader = new DataFileStream<>(input, new GenericDatumReader<>());

      if (schema == null) {
        // this is the first file - set up the writer, and store the
        // Schema & metadata we'll use.
        schema = reader.getSchema();
        for (String key : reader.getMetaKeys()) {
          if (!DataFileWriter.isReservedMeta(key)) {
            byte[] metadatum = reader.getMeta(key);
            metadata.put(key, metadatum);
            writer.setMeta(key, metadatum);
          }
        }
        inputCodec = reader.getMetaString(DataFileConstants.CODEC);
        if (inputCodec == null) {
          inputCodec = DataFileConstants.NULL_CODEC;
        }
        writer.setCodec(CodecFactory.fromString(inputCodec));
        writer.create(schema, output);
      } else {
        // check that we're appending to the same schema & metadata.
        if (!schema.equals(reader.getSchema())) {
          err.println("input files have different schemas");
          reader.close();
          return 1;
        }
        for (String key : reader.getMetaKeys()) {
          if (!DataFileWriter.isReservedMeta(key)) {
            byte[] metadatum = reader.getMeta(key);
            byte[] writersMetadatum = metadata.get(key);
            if (!Arrays.equals(metadatum, writersMetadatum)) {
              err.println("input files have different non-reserved metadata");
              reader.close();
              return 2;
            }
          }
        }
        String thisCodec = reader.getMetaString(DataFileConstants.CODEC);
        if (thisCodec == null) {
          thisCodec = DataFileConstants.NULL_CODEC;
        }
        if (!inputCodec.equals(thisCodec)) {
          err.println("input files have different codecs");
          reader.close();
          return 3;
        }
      }

      writer.appendAllFrom(reader, /* recompress */ false);
      reader.close();
    }

    writer.close();
    return 0;
  }

  /** Processes a list of input files to expand directories if needed. */
  private static List expandsInputFiles(List args) throws IOException {
    List files = new ArrayList<>();

    for (String arg : args) {
      if (arg.equals("-")) {
        files.add(arg);
      } else {
        List paths = Util.getFiles(arg);
        for (Path path : paths) {
          files.add(path.toString());
        }
      }
    }

    return files;
  }

  private void printHelp(PrintStream out) {
    out.println("concat [input-file...] output-file");
    out.println();
    out.println("Concatenates one or more input files into a new output file");
    out.println("by appending the input blocks without decoding them. The input");
    out.println("files must have the same schema, metadata and codec. If they");
    out.println("do not the tool will return the following error codes:");
    out.println("  1 if the schemas don't match");
    out.println("  2 if the metadata doesn't match");
    out.println("  3 if the codecs don't match");
    out.println("If no input files are given stdin will be used. The tool");
    out.println("0 on success. A dash ('-') can be given as an input file");
    out.println("to use stdin, and as an output file to use stdout. If a directory");
    out.println("is given as an input-file all the files within this directory");
    out.println("are used.");
  }

  @Override
  public String getName() {
    return "concat";
  }

  @Override
  public String getShortDescription() {
    return "Concatenates avro files without re-compressing.";
  }
}