hadoop ErasureDecoder 源码

  • 2022-10-20
  • 浏览 (546)

haddop ErasureDecoder 代码

文件路径:/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/coder/ErasureDecoder.java

/**
 * 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.conf.Configured;
import org.apache.hadoop.io.erasurecode.ECBlock;
import org.apache.hadoop.io.erasurecode.ECBlockGroup;
import org.apache.hadoop.io.erasurecode.ErasureCoderOptions;

/**
 * An abstract erasure decoder that's to be inherited by new decoders.
 *
 * It implements the {@link ErasureCoder} interface.
 */
@InterfaceAudience.Private
public abstract class ErasureDecoder extends Configured
    implements ErasureCoder {
  private final int numDataUnits;
  private final int numParityUnits;
  private final ErasureCoderOptions options;

  public ErasureDecoder(ErasureCoderOptions options) {
    this.options = options;
    this.numDataUnits = options.getNumDataUnits();
    this.numParityUnits = options.getNumParityUnits();
  }

  @Override
  public ErasureCodingStep calculateCoding(ECBlockGroup blockGroup) {
    // We may have more than this when considering complicate cases. HADOOP-11550
    return prepareDecodingStep(blockGroup);
  }

  @Override
  public int getNumDataUnits() {
    return this.numDataUnits;
  }

  @Override
  public int getNumParityUnits() {
    return this.numParityUnits;
  }

  @Override
  public ErasureCoderOptions getOptions() {
    return options;
  }

  /**
   * We have all the data blocks and parity blocks as input blocks for
   * recovering by default. It's codec specific
   * @param blockGroup blockGroup.
   * @return input blocks
   */
  protected ECBlock[] getInputBlocks(ECBlockGroup blockGroup) {
    ECBlock[] inputBlocks = new ECBlock[getNumDataUnits() +
            getNumParityUnits()];

    System.arraycopy(blockGroup.getDataBlocks(), 0, inputBlocks,
            0, getNumDataUnits());

    System.arraycopy(blockGroup.getParityBlocks(), 0, inputBlocks,
            getNumDataUnits(), getNumParityUnits());

    return inputBlocks;
  }

  /**
   * Which blocks were erased ?
   * @param blockGroup blockGroup.
   * @return output blocks to recover
   */
  protected ECBlock[] getOutputBlocks(ECBlockGroup blockGroup) {
    ECBlock[] outputBlocks = new ECBlock[getNumErasedBlocks(blockGroup)];

    int idx = 0;

    for (int i = 0; i < getNumDataUnits(); i++) {
      if (blockGroup.getDataBlocks()[i].isErased()) {
        outputBlocks[idx++] = blockGroup.getDataBlocks()[i];
      }
    }

    for (int i = 0; i < getNumParityUnits(); i++) {
      if (blockGroup.getParityBlocks()[i].isErased()) {
        outputBlocks[idx++] = blockGroup.getParityBlocks()[i];
      }
    }

    return outputBlocks;
  }

  @Override
  public boolean preferDirectBuffer() {
    return false;
  }

  @Override
  public void release() {
    // Nothing to do by default
  }

  /**
   * Perform decoding against a block blockGroup.
   * @param blockGroup blockGroup.
   * @return decoding step for caller to do the real work
   */
  protected abstract ErasureCodingStep prepareDecodingStep(
      ECBlockGroup blockGroup);

  /**
   * Get the number of erased blocks in the block group.
   * @param blockGroup blockGroup.
   * @return number of erased blocks
   */
  protected int getNumErasedBlocks(ECBlockGroup blockGroup) {
    int num = getNumErasedBlocks(blockGroup.getParityBlocks());
    num += getNumErasedBlocks(blockGroup.getDataBlocks());
    return num;
  }

  /**
   * Find out how many blocks are erased.
   * @param inputBlocks all the input blocks
   * @return number of erased blocks
   */
  protected static int getNumErasedBlocks(ECBlock[] inputBlocks) {
    int numErased = 0;
    for (int i = 0; i < inputBlocks.length; i++) {
      if (inputBlocks[i].isErased()) {
        numErased ++;
      }
    }

    return numErased;
  }

  /**
   * Get indexes of erased blocks from inputBlocks
   * @param inputBlocks inputBlocks.
   * @return indexes of erased blocks from inputBlocks
   */
  protected int[] getErasedIndexes(ECBlock[] inputBlocks) {
    int numErased = getNumErasedBlocks(inputBlocks);
    if (numErased == 0) {
      return new int[0];
    }

    int[] erasedIndexes = new int[numErased];
    int i = 0, j = 0;
    for (; i < inputBlocks.length && j < erasedIndexes.length; i++) {
      if (inputBlocks[i].isErased()) {
        erasedIndexes[j++] = i;
      }
    }

    return erasedIndexes;
  }
}

相关信息

hadoop 源码目录

相关文章

hadoop DummyErasureDecoder 源码

hadoop DummyErasureEncoder 源码

hadoop ErasureCoder 源码

hadoop ErasureCodingStep 源码

hadoop ErasureDecodingStep 源码

hadoop ErasureEncoder 源码

hadoop ErasureEncodingStep 源码

hadoop HHErasureCodingStep 源码

hadoop HHXORErasureDecoder 源码

hadoop HHXORErasureDecodingStep 源码

0  赞