hadoop HHXORErasureDecodingStep 源码

haddop HHXORErasureDecodingStep 代码

文件路径：/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/coder/HHXORErasureDecodingStep.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 java.io.IOException;
import java.nio.ByteBuffer;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.io.erasurecode.ECBlock;
import org.apache.hadoop.io.erasurecode.ECChunk;
import org.apache.hadoop.io.erasurecode.coder.util.HHUtil;
import org.apache.hadoop.io.erasurecode.rawcoder.RawErasureDecoder;
import org.apache.hadoop.io.erasurecode.rawcoder.RawErasureEncoder;

/**
 * Hitchhiker-XOR Erasure decoding step, a wrapper of all the necessary
 * information to perform a decoding step involved in the whole process of
 * decoding a block group.
 */
@InterfaceAudience.Private
public class HHXORErasureDecodingStep extends HHErasureCodingStep {
  private int pbIndex;
  private int[] piggyBackIndex;
  private int[] piggyBackFullIndex;
  private int[] erasedIndexes;
  private RawErasureDecoder rsRawDecoder;
  private RawErasureEncoder xorRawEncoder;

  /**
   * The constructor with all the necessary info.
   * @param inputBlocks inputBlocks.
   * @param erasedIndexes the indexes of erased blocks in inputBlocks array
   * @param outputBlocks outputBlocks.
   * @param rawDecoder underlying RS decoder for hitchhiker decoding
   * @param rawEncoder underlying XOR encoder for hitchhiker decoding
   */
  public HHXORErasureDecodingStep(ECBlock[] inputBlocks, int[] erasedIndexes,
      ECBlock[] outputBlocks, RawErasureDecoder rawDecoder,
      RawErasureEncoder rawEncoder) {
    super(inputBlocks, outputBlocks);
    this.pbIndex = rawDecoder.getNumParityUnits() - 1;
    this.erasedIndexes = erasedIndexes;
    this.rsRawDecoder = rawDecoder;
    this.xorRawEncoder = rawEncoder;

    this.piggyBackIndex = HHUtil.initPiggyBackIndexWithoutPBVec(
        rawDecoder.getNumDataUnits(), rawDecoder.getNumParityUnits());
    this.piggyBackFullIndex = HHUtil.initPiggyBackFullIndexVec(
        rawDecoder.getNumDataUnits(), piggyBackIndex);
  }

  @Override
  public void performCoding(ECChunk[] inputChunks, ECChunk[] outputChunks)
      throws IOException {
    if (erasedIndexes.length == 0) {
      return;
    }

    ByteBuffer[] inputBuffers = ECChunk.toBuffers(inputChunks);
    ByteBuffer[] outputBuffers = ECChunk.toBuffers(outputChunks);
    performCoding(inputBuffers, outputBuffers);
  }

  private void performCoding(ByteBuffer[] inputs, ByteBuffer[] outputs)
      throws IOException {
    final int numDataUnits = rsRawDecoder.getNumDataUnits();
    final int numParityUnits = rsRawDecoder.getNumParityUnits();
    final int numTotalUnits = numDataUnits + numParityUnits;
    final int subPacketSize = getSubPacketSize();

    ByteBuffer fisrtValidInput = HHUtil.findFirstValidInput(inputs);
    final int bufSize = fisrtValidInput.remaining();

    if (inputs.length != numTotalUnits * getSubPacketSize()) {
      throw new IllegalArgumentException("Invalid inputs length");
    }

    if (outputs.length != erasedIndexes.length * getSubPacketSize()) {
      throw new IllegalArgumentException("Invalid outputs length");
    }

    // notes:inputs length = numDataUnits * subPacketizationSize
    // first numDataUnits length is first sub-stripe,
    // second numDataUnits length is second sub-stripe
    ByteBuffer[][] newIn = new ByteBuffer[subPacketSize][numTotalUnits];
    for (int i = 0; i < subPacketSize; ++i) {
      for (int j = 0; j < numTotalUnits; ++j) {
        newIn[i][j] = inputs[i * numTotalUnits + j];
      }
    }

    ByteBuffer[][] newOut = new ByteBuffer[subPacketSize][erasedIndexes.length];
    for (int i = 0; i < subPacketSize; ++i) {
      for (int j = 0; j < erasedIndexes.length; ++j) {
        newOut[i][j] = outputs[i * erasedIndexes.length + j];
      }
    }

    if (erasedIndexes.length == 1 && erasedIndexes[0] < numDataUnits) {
      // Only reconstruct one data unit missing
      doDecodeSingle(newIn, newOut, erasedIndexes[0], bufSize,
              fisrtValidInput.isDirect());
    } else {
      doDecodeMultiAndParity(newIn, newOut, erasedIndexes, bufSize);
    }
  }

  private void doDecodeSingle(ByteBuffer[][] inputs, ByteBuffer[][] outputs,
                              int erasedLocationToFix, int bufSize,
                              boolean isDirect) throws IOException {
    final int numDataUnits = rsRawDecoder.getNumDataUnits();
    final int numParityUnits = rsRawDecoder.getNumParityUnits();
    final int subPacketSize = getSubPacketSize();

    int[][] inputPositions = new int[subPacketSize][inputs[0].length];
    for (int i = 0; i < subPacketSize; ++i) {
      for (int j = 0; j < inputs[i].length; ++j) {
        if (inputs[i][j] != null) {
          inputPositions[i][j] = inputs[i][j].position();
        }
      }
    }

    ByteBuffer[] tempInputs = new ByteBuffer[numDataUnits + numParityUnits];
    for (int i = 0; i < tempInputs.length; ++i) {
      tempInputs[i] = inputs[1][i];
    }

    ByteBuffer[][] tmpOutputs = new ByteBuffer[subPacketSize][numParityUnits];
    for (int i = 0; i < getSubPacketSize(); ++i) {
      for (int j = 0; j < erasedIndexes.length; ++j) {
        tmpOutputs[i][j] = outputs[i][j];
      }

      for (int m = erasedIndexes.length; m < numParityUnits; ++m) {
        tmpOutputs[i][m] = HHUtil.allocateByteBuffer(isDirect, bufSize);
      }
    }

    // First consider the second subPacket
    int[] erasedLocation = new int[numParityUnits];
    erasedLocation[0] = erasedLocationToFix;

    // assign the erased locations based on the locations not read for
    // second subPacket but from decoding
    for (int i = 1; i < numParityUnits; i++) {
      erasedLocation[i] = numDataUnits + i;
      tempInputs[numDataUnits + i] = null;
    }

    rsRawDecoder.decode(tempInputs, erasedLocation, tmpOutputs[1]);

    int piggyBackParityIndex = piggyBackFullIndex[erasedLocationToFix];
    ByteBuffer piggyBack = HHUtil.getPiggyBackForDecode(inputs, tmpOutputs,
            piggyBackParityIndex, numDataUnits, numParityUnits, pbIndex);

    // Second consider the first subPacket.
    // get the value of the piggyback associated with the erased location
    if (isDirect) {
      // decode the erased value in the first subPacket by using the piggyback
      int idxToWrite = 0;
      doDecodeByPiggyBack(inputs[0], tmpOutputs[0][idxToWrite], piggyBack,
              erasedLocationToFix);
    } else {
      ByteBuffer buffer;
      byte[][][] newInputs = new byte[getSubPacketSize()][inputs[0].length][];
      int[][] inputOffsets = new int[getSubPacketSize()][inputs[0].length];
      byte[][][] newOutputs = new byte[getSubPacketSize()][numParityUnits][];
      int[][] outOffsets = new int[getSubPacketSize()][numParityUnits];

      for (int i = 0; i < getSubPacketSize(); ++i) {
        for (int j = 0; j < inputs[0].length; ++j) {
          buffer = inputs[i][j];
          if (buffer != null) {
            inputOffsets[i][j] = buffer.arrayOffset() + buffer.position();
            newInputs[i][j] = buffer.array();
          }
        }
      }

      for (int i = 0; i < getSubPacketSize(); ++i) {
        for (int j = 0; j < numParityUnits; ++j) {
          buffer = tmpOutputs[i][j];
          if (buffer != null) {
            outOffsets[i][j] = buffer.arrayOffset() + buffer.position();
            newOutputs[i][j] = buffer.array();
          }
        }
      }

      byte[] newPiggyBack = piggyBack.array();

      // decode the erased value in the first subPacket by using the piggyback
      int idxToWrite = 0;
      doDecodeByPiggyBack(newInputs[0], inputOffsets[0],
              newOutputs[0][idxToWrite], outOffsets[0][idxToWrite],
              newPiggyBack, erasedLocationToFix, bufSize);
    }

    for (int i = 0; i < subPacketSize; ++i) {
      for (int j = 0; j < inputs[i].length; ++j) {
        if (inputs[i][j] != null) {
          inputs[i][j].position(inputPositions[i][j] + bufSize);
        }
      }
    }
  }

  private void doDecodeByPiggyBack(ByteBuffer[] inputs,
                                   ByteBuffer outputs,
                                   ByteBuffer piggyBack,
                                   int erasedLocationToFix) {
    final int thisPiggyBackSetIdx = piggyBackFullIndex[erasedLocationToFix];
    final int startIndex = piggyBackIndex[thisPiggyBackSetIdx - 1];
    final int endIndex = piggyBackIndex[thisPiggyBackSetIdx];

    // recover first sub-stripe data by XOR piggyback
    int bufSize = piggyBack.remaining();
    for (int i = piggyBack.position();
         i < piggyBack.position() + bufSize; i++) {
      for (int j = startIndex; j < endIndex; j++) {
        if (inputs[j] != null) {
          piggyBack.put(i, (byte)
                  (piggyBack.get(i) ^ inputs[j].get(inputs[j].position() + i)));
        }
      }
      outputs.put(outputs.position() + i, piggyBack.get(i));
    }
  }

  private void doDecodeByPiggyBack(byte[][] inputs, int[] inputOffsets,
                                   byte[] outputs, int outOffset,
                                   byte[] piggyBack, int erasedLocationToFix,
                                   int bufSize) {
    final int thisPiggyBackSetIdx = piggyBackFullIndex[erasedLocationToFix];
    final int startIndex = piggyBackIndex[thisPiggyBackSetIdx - 1];
    final int endIndex = piggyBackIndex[thisPiggyBackSetIdx];

    // recover first sub-stripe data by XOR piggyback
    for (int i = 0; i < bufSize; i++) {
      for (int j = startIndex; j < endIndex; j++) {
        if (inputs[j] != null) {
          piggyBack[i] = (byte) (piggyBack[i] ^ inputs[j][i + inputOffsets[j]]);
        }
      }
      outputs[i + outOffset] = piggyBack[i];
    }
  }

  private void doDecodeMultiAndParity(ByteBuffer[][] inputs,
                                      ByteBuffer[][] outputs,
                                      int[] erasedLocationToFix, int bufSize)
      throws IOException {
    final int numDataUnits = rsRawDecoder.getNumDataUnits();
    final int numParityUnits = rsRawDecoder.getNumParityUnits();
    final int numTotalUnits = numDataUnits + numParityUnits;
    int[] parityToFixFlag = new int[numTotalUnits];

    for (int i = 0; i < erasedLocationToFix.length; ++i) {
      if (erasedLocationToFix[i] >= numDataUnits) {
        parityToFixFlag[erasedLocationToFix[i]] = 1;
      }
    }

    int[] inputPositions = new int[inputs[0].length];
    for (int i = 0; i < inputPositions.length; i++) {
      if (inputs[0][i] != null) {
        inputPositions[i] = inputs[0][i].position();
      }
    }

    // decoded first sub-stripe
    rsRawDecoder.decode(inputs[0], erasedLocationToFix, outputs[0]);

    for (int i = 0; i < inputs[0].length; i++) {
      if (inputs[0][i] != null) {
        // dataLen bytes consumed
        inputs[0][i].position(inputPositions[i]);
      }
    }

    ByteBuffer[] tempInput = new ByteBuffer[numDataUnits];
    for (int i = 0; i < numDataUnits; ++i) {
      tempInput[i] = inputs[0][i];
//
//      if (!isDirect && tempInput[i] != null) {
//        tempInput[i].position(tempInput[i].position() - bufSize);
//      }
    }

    for (int i = 0; i < erasedLocationToFix.length; ++i) {
      if (erasedLocationToFix[i] < numDataUnits) {
        tempInput[erasedLocationToFix[i]] = outputs[0][i];
      }
    }

    ByteBuffer[] piggyBack = HHUtil.getPiggyBacksFromInput(tempInput,
            piggyBackIndex, numParityUnits, 0, xorRawEncoder);

    for (int j = numDataUnits + 1; j < numTotalUnits; ++j) {
      if (parityToFixFlag[j] == 0 && inputs[1][j] != null) {
        // f(b) + f(a1,a2,a3....)
        for (int k = inputs[1][j].position(),
             m = piggyBack[j - numDataUnits - 1].position();
             k < inputs[1][j].limit(); ++k, ++m) {
          inputs[1][j].put(k, (byte)
                  (inputs[1][j].get(k) ^
                          piggyBack[j - numDataUnits - 1].get(m)));
        }
      }
    }

    // decoded second sub-stripe
    rsRawDecoder.decode(inputs[1], erasedLocationToFix, outputs[1]);

    // parity index = 0, the data have no piggyBack
    for (int j = 0; j < erasedLocationToFix.length; ++j) {
      if (erasedLocationToFix[j] < numTotalUnits
              && erasedLocationToFix[j] > numDataUnits) {
        int parityIndex = erasedLocationToFix[j] - numDataUnits - 1;
        for (int k = outputs[1][j].position(),
             m = piggyBack[parityIndex].position();
             k < outputs[1][j].limit(); ++k, ++m) {
          outputs[1][j].put(k, (byte)
                  (outputs[1][j].get(k) ^ piggyBack[parityIndex].get(m)));
        }
      }
    }

    for (int i = 0; i < inputs[0].length; i++) {
      if (inputs[0][i] != null) {
        // dataLen bytes consumed
        inputs[0][i].position(inputPositions[i] + bufSize);
      }
    }
  }

}

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 ErasureDecoder 源码

hadoop ErasureDecodingStep 源码

hadoop ErasureEncoder 源码

hadoop ErasureEncodingStep 源码

hadoop HHErasureCodingStep 源码

hadoop HHXORErasureDecoder 源码