void init(Configuration conf, FSDataOutputStream out,
        CompressionCodec codec, Metadata metadata) throws IOException {
      this.conf = conf;
      this.out = out;
      this.codec = codec;
      this.metadata = metadata;
      this.useNewMagic = conf.getBoolean(HIVE_USE_EXPLICIT_RCFILE_HEADER.varname, true);
    }
Write and flush the file header.
ql/src/java/org/apache/hadoop/hive/ql/io/RCFile.java