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.
   */
  package org.apache.hadoop.io.erasurecode.coder;
  
  import org.apache.hadoop.classification.InterfaceAudience;
  import org.apache.hadoop.io.erasurecode.CodecUtil;
  import org.apache.hadoop.io.erasurecode.ECBlock;
  import org.apache.hadoop.io.erasurecode.ECBlockGroup;
  import org.apache.hadoop.io.erasurecode.ErasureCodeConstants;
  import org.apache.hadoop.io.erasurecode.ErasureCoderOptions;
  import org.apache.hadoop.io.erasurecode.rawcoder.RawErasureDecoder;
  
  /**
   * Reed-Solomon erasure decoder that decodes a block group.
   *
   * It implements {@link ErasureCoder}.
   */
  @InterfaceAudience.Private
  public class RSErasureDecoder extends ErasureDecoder {
    private RawErasureDecoder rsRawDecoder;
  
    public RSErasureDecoder(ErasureCoderOptions options) {
      super(options);
    }
  
    @Override
    protected ErasureCodingStep prepareDecodingStep(final ECBlockGroup blockGroup) {
  
      ECBlock[] inputBlocks = getInputBlocks(blockGroup);
      ECBlock[] outputBlocks = getOutputBlocks(blockGroup);
  
      RawErasureDecoder rawDecoder = checkCreateRSRawDecoder();
      return new ErasureDecodingStep(inputBlocks,
          getErasedIndexes(inputBlocks), outputBlocks, rawDecoder);
    }
  
    private RawErasureDecoder checkCreateRSRawDecoder() {
      if (rsRawDecoder == null) {
        rsRawDecoder = CodecUtil.createRawDecoder(getConf(),
            ErasureCodeConstants.RS_CODEC_NAME, getOptions());
      }
      return rsRawDecoder;
    }
  
    @Override
    public void release() {
      if (rsRawDecoder != null) {
        rsRawDecoder.release();
      }
    }
  }
  