Package com.tangosol.io

Class 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 Detail

      • 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:
        Constant Field Values

      • 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:
        Constant Field Values

      • 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:
        Constant Field Values

      • 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:
        Constant Field Values

      • 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:
        Constant Field Values

      • MIN_BLOCK

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

      • 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 Detail

      • BinaryDeltaCompressor

        public BinaryDeltaCompressor()
        Default constructor.

    • Method Detail

      • 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

      • 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