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Oracle® Coherence Java API Reference
Release 3.7.0.0

E18683-01


com.tangosol.io
Class BinaryDeltaCompressor

java.lang.Object
  extended by com.tangosol.io.BinaryDeltaCompressor

All Implemented Interfaces:
DeltaCompressor
Direct Known Subclasses:
PofDeltaCompressor

public class BinaryDeltaCompressor
extends java.lang.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 Summary
protected static Binary DELTA_TRUNCATE
          A delta value that indicates an empty new value.
protected static 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.
protected static 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.
protected static 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.
protected static int MIN_BLOCK
          Minimum length of an "extract" block to encode.
protected static Binary NO_BINARY
          An empty Binary object.
protected static 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.
protected static 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.
protected static 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.

 

Constructor Summary
BinaryDeltaCompressor()
          Default constructor.

 

Method Summary
 ReadBuffer applyDelta(ReadBuffer bufOld, ReadBuffer bufDelta)
          Apply a delta to an old value in order to create a new value.
protected  ReadBuffer createDelta(ReadBuffer bufOld, ReadBuffer bufNew)
          Actually create a delta in the binary delta format.
 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.

 

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

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:
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

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

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Oracle® Coherence Java API Reference
Release 3.7.0.0

E18683-01


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