Package com.tangosol.io

Class BinaryDeltaCompressor

java.lang.Object
com.tangosol.io.BinaryDeltaCompressor
All Implemented Interfaces:
DeltaCompressor
Direct Known Subclasses:
PofDeltaCompressor
public class BinaryDeltaCompressor extends Object implements DeltaCompressor
A DeltaCompressor implementation that works with opaque (binary) values.

The delta format is composed of a leading byte that indicates the format; the format indicator byte is one of the FMT_* field values. If the delta value does not begin with one of the FMT_* indicators, then the delta value is itself the new value. If the delta is null, then it indicates no change. The grammar follows: 

 BinaryDelta:
   FMT_EMPTY
   FMT_BINDIFF BinaryChangeList-opt OP_TERM
   FMT_REPLACE-opt Bytes
   null

 BinaryChangeList:
   OP_EXTRACT Offset Length BinaryChangeList-opt
   OP_APPEND Length Bytes BinaryChangeList-opt

 Offset:
 Length:
   packed-integer

 Bytes:
   byte Bytes-opt
Author:
cp 2009.01.06

  • Field Details

    • FMT_EMPTY

      protected static final byte FMT_EMPTY
      A format indicator (the first byte of the binary delta) that indicates that the new value is a zero-length binary value.
      See Also:

    • FMT_REPLACE

      protected static final byte FMT_REPLACE
      A format indicator (the first byte of the binary delta) that indicates that the new value is found in its entirety in the delta value. In other words, other than the first byte, the delta is itself the new value.
      See Also:

    • FMT_BINDIFF

      protected static final byte FMT_BINDIFF
      A format indicator (the first byte of the binary delta) that indicates that the new value is formed by applying a series of modifications to the old value. The possible modifications are defined by the OP_* constants.
      See Also:

    • OP_EXTRACT

      protected static final byte OP_EXTRACT
      A binary delta operator that instructs the applyDelta(com.tangosol.io.ReadBuffer, com.tangosol.io.ReadBuffer) method to extract bytes from the old value and append them to the new value. The format is the one-byte OP_EXTRACT indicator followed by a packed int offset and packed int length. The offset and length indicate the region of the old value to extract and append to the new value.
      See Also:

    • OP_APPEND

      protected static final byte OP_APPEND
      A binary delta operator that instructs the applyDelta(com.tangosol.io.ReadBuffer, com.tangosol.io.ReadBuffer) method to copy the following bytes from the delta value and append them to the new value. The format is the one-byte OP_APPEND indicator followed by a packed int length and then a series of bytes. The length indicates the length of the series of bytes to copy from the delta value and append to the new value.
      See Also:

    • OP_TERM

      protected static final byte OP_TERM
      A binary delta operator that instructs the applyDelta(com.tangosol.io.ReadBuffer, com.tangosol.io.ReadBuffer) method that the delta has been fully applied.
      See Also:

    • MIN_BLOCK

      protected static final int MIN_BLOCK
      Minimum length of an "extract" block to encode.
      See Also:

    • NO_BINARY

      protected static final Binary NO_BINARY
      An empty Binary object.

    • DELTA_TRUNCATE

      protected static final Binary DELTA_TRUNCATE
      A delta value that indicates an empty new value.

  • Constructor Details

    • BinaryDeltaCompressor

      public BinaryDeltaCompressor()
      Default constructor.

  • Method Details

    • extractDelta

      public ReadBuffer extractDelta(ReadBuffer bufOld, ReadBuffer bufNew)
      Compare an old value to a new value and generate a delta that represents the changes that must be made to the old value in order to transform it into the new value. The generated delta must be a ReadBuffer of non-zero length.

      If the old value is null, the generated delta must be a "replace", meaning that applying it to any value must produce the specified new value.

      Specified by:
      extractDelta in interface DeltaCompressor
      Parameters:
      bufOld - the old value
      bufNew - the new value; must not be null
      Returns:
      the changes that must be made to the old value in order to transform it into the new value, or null to indicate no change

    • applyDelta

      public ReadBuffer applyDelta(ReadBuffer bufOld, ReadBuffer bufDelta)
      Apply a delta to an old value in order to create a new value.
      Specified by:
      applyDelta in interface DeltaCompressor
      Parameters:
      bufOld - the old value
      bufDelta - the delta information returned from DeltaCompressor.extractDelta(com.tangosol.io.ReadBuffer, com.tangosol.io.ReadBuffer) to apply to the old value
      Returns:
      the new value

    • createDelta

      protected ReadBuffer createDelta(ReadBuffer bufOld, ReadBuffer bufNew)
      Actually create a delta in the binary delta format. This method is designed to be overridden by subclasses that have more intimate knowledge of the contents of the buffers.
      Parameters:
      bufOld - the old value
      bufNew - the new value
      Returns:
      a delta in the binary delta format