Package org.apache.hadoop.io.erasurecode.coder

Class ErasureDecoder

java.lang.Object
org.apache.hadoop.conf.Configured
org.apache.hadoop.io.erasurecode.coder.ErasureDecoder
All Implemented Interfaces:
Configurable, ErasureCoder
Direct Known Subclasses:
DummyErasureDecoder, HHXORErasureDecoder, RSErasureDecoder, XORErasureDecoder
@Private public abstract class ErasureDecoder extends Configured implements ErasureCoder
An abstract erasure decoder that's to be inherited by new decoders. It implements the ErasureCoder interface.

  • Constructor Details

  • Method Details

    • calculateCoding

      public ErasureCodingStep calculateCoding(ECBlockGroup blockGroup)
      Description copied from interface: ErasureCoder
      Calculate the encoding or decoding steps given a block blockGroup. Note, currently only one coding step is supported. Will support complex cases of multiple coding steps.
      Specified by:
      calculateCoding in interface ErasureCoder
      Parameters:
      blockGroup - the erasure coding block group containing all necessary information for codec calculation
      Returns:
      ErasureCodingStep.

    • getNumDataUnits

      public int getNumDataUnits()
      Description copied from interface: ErasureCoder
      The number of data input units for the coding. A unit can be a byte, chunk or buffer or even a block.
      Specified by:
      getNumDataUnits in interface ErasureCoder
      Returns:
      count of data input units

    • getNumParityUnits

      public int getNumParityUnits()
      Description copied from interface: ErasureCoder
      The number of parity output units for the coding. A unit can be a byte, chunk, buffer or even a block.
      Specified by:
      getNumParityUnits in interface ErasureCoder
      Returns:
      count of parity output units

    • getOptions

      public ErasureCoderOptions getOptions()
      Description copied from interface: ErasureCoder
      The options of erasure coder. This option is passed to raw erasure coder as it is.
      Specified by:
      getOptions in interface ErasureCoder
      Returns:
      erasure coder options

    • getInputBlocks

      protected ECBlock[] getInputBlocks(ECBlockGroup blockGroup)
      We have all the data blocks and parity blocks as input blocks for recovering by default. It's codec specific
      Parameters:
      blockGroup - blockGroup.
      Returns:
      input blocks

    • getOutputBlocks

      protected ECBlock[] getOutputBlocks(ECBlockGroup blockGroup)
      Which blocks were erased ?
      Parameters:
      blockGroup - blockGroup.
      Returns:
      output blocks to recover

    • preferDirectBuffer

      public boolean preferDirectBuffer()
      Description copied from interface: ErasureCoder
      Tell if direct or off-heap buffer is preferred or not. It's for callers to decide how to allocate coding chunk buffers, either on heap or off heap. It will return false by default.
      Specified by:
      preferDirectBuffer in interface ErasureCoder
      Returns:
      true if direct buffer is preferred for performance consideration, otherwise false.

    • release

      public void release()
      Description copied from interface: ErasureCoder
      Release the resources if any. Good chance to invoke RawErasureCoder#release.
      Specified by:
      release in interface ErasureCoder

    • prepareDecodingStep

      protected abstract ErasureCodingStep prepareDecodingStep(ECBlockGroup blockGroup)
      Perform decoding against a block blockGroup.
      Parameters:
      blockGroup - blockGroup.
      Returns:
      decoding step for caller to do the real work

    • getNumErasedBlocks

      protected int getNumErasedBlocks(ECBlockGroup blockGroup)
      Get the number of erased blocks in the block group.
      Parameters:
      blockGroup - blockGroup.
      Returns:
      number of erased blocks

    • getNumErasedBlocks

      protected static int getNumErasedBlocks(ECBlock[] inputBlocks)
      Find out how many blocks are erased.
      Parameters:
      inputBlocks - all the input blocks
      Returns:
      number of erased blocks

    • getErasedIndexes

      protected int[] getErasedIndexes(ECBlock[] inputBlocks)
      Get indexes of erased blocks from inputBlocks
      Parameters:
      inputBlocks - inputBlocks.
      Returns:
      indexes of erased blocks from inputBlocks