CodecUtil.java example

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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.hadoop.io.erasurecode;

import com.google.common.base.Preconditions;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.CommonConfigurationKeys;
import org.apache.hadoop.io.erasurecode.rawcoder.RawErasureCoderFactory;
import org.apache.hadoop.io.erasurecode.rawcoder.RawErasureDecoder;
import org.apache.hadoop.io.erasurecode.rawcoder.RawErasureEncoder;

/**
 * A codec & coder utility to help create raw coders conveniently.
 */
@InterfaceAudience.Private
public final class CodecUtil {

  private CodecUtil() { }

  /**
   * Create RS raw encoder according to configuration.
   * @param conf configuration
   * @param coderOptions coder options that's used to create the coder
   * @param codec the codec to use. If null, will use the default codec
   * @return raw encoder
   */
  public static RawErasureEncoder createRawEncoder(
      Configuration conf, String codec, ErasureCoderOptions coderOptions) {
    Preconditions.checkNotNull(conf);
    Preconditions.checkNotNull(codec);

    String rawCoderFactoryKey = getFactNameFromCodec(conf, codec);

    RawErasureCoderFactory fact = createRawCoderFactory(conf,
        rawCoderFactoryKey);

    return fact.createEncoder(coderOptions);
  }

  /**
   * Create RS raw decoder according to configuration.
   * @param conf configuration
   * @param coderOptions coder options that's used to create the coder
   * @param codec the codec to use. If null, will use the default codec
   * @return raw decoder
   */
  public static RawErasureDecoder createRawDecoder(
      Configuration conf, String codec, ErasureCoderOptions coderOptions) {
    Preconditions.checkNotNull(conf);
    Preconditions.checkNotNull(codec);

    String rawCoderFactoryKey = getFactNameFromCodec(conf, codec);

    RawErasureCoderFactory fact = createRawCoderFactory(conf,
        rawCoderFactoryKey);

    return fact.createDecoder(coderOptions);
  }

  private static RawErasureCoderFactory createRawCoderFactory(
      Configuration conf, String rawCoderFactoryKey) {
    RawErasureCoderFactory fact;
    try {
      Class<? extends RawErasureCoderFactory> factClass = conf.getClassByName(
          rawCoderFactoryKey).asSubclass(RawErasureCoderFactory.class);
      fact = factClass.newInstance();
    } catch (ClassNotFoundException | InstantiationException |
        IllegalAccessException e) {
      throw new RuntimeException("Failed to create raw coder factory", e);
    }

    if (fact == null) {
      throw new RuntimeException("Failed to create raw coder factory");
    }

    return fact;
  }

  private static String getFactNameFromCodec(Configuration conf, String codec) {
    switch (codec) {
    case ErasureCodeConstants.RS_DEFAULT_CODEC_NAME:
      return conf.get(
          CommonConfigurationKeys.IO_ERASURECODE_CODEC_RS_DEFAULT_RAWCODER_KEY,
          CommonConfigurationKeys.
              IO_ERASURECODE_CODEC_RS_DEFAULT_RAWCODER_DEFAULT);
    case ErasureCodeConstants.RS_LEGACY_CODEC_NAME:
      return conf.get(
          CommonConfigurationKeys.IO_ERASURECODE_CODEC_RS_LEGACY_RAWCODER_KEY,
          CommonConfigurationKeys.
              IO_ERASURECODE_CODEC_RS_LEGACY_RAWCODER_DEFAULT);
    case ErasureCodeConstants.XOR_CODEC_NAME:
      return conf.get(
          CommonConfigurationKeys.IO_ERASURECODE_CODEC_XOR_RAWCODER_KEY,
          CommonConfigurationKeys.IO_ERASURECODE_CODEC_XOR_RAWCODER_DEFAULT);
    default:
      // For custom codec, we throw exception if the factory is not configured
      String rawCoderKey = "io.erasurecode.codec." + codec + ".rawcoder";
      String factName = conf.get(rawCoderKey);
      if (factName == null) {
        throw new IllegalArgumentException("Raw coder factory not configured " +
            "for custom codec " + codec);
      }
      return factName;
    }
  }
}